Re: Functions help
In article mailman.7297.1393204171.18130.python-l...@python.org, Mark Lawrence breamore...@yahoo.co.uk wrote: On 24/02/2014 00:55, alex23 wrote: On 23/02/2014 3:43 PM, Scott W Dunning wrote: I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. Meaning is there a way I can call a function and then add *5 or something like that? The same way you repeat anything in Python: with a loop construct. for _ in range(5): func() For the benefit of newbies, besides the obvious indentation error above, the underscore basically acts as a dummy variable. I'll let the language lawyers give a very detailed, precise description :) As far as I know, it's purely convention. _ is a legal variable name in Python, and the convention is that unpacking something into _ means, I don't care about that value. It's also used to ignore several values: _, _, foo, bar, _ = blah unpacks a 5-tuple, of which you only care about the 3rd and 4th values. -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 2014-02-24, Benjamin Kaplan benjamin.kap...@case.edu wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( -- Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. It was also fine here reading comp.lang.python using slrn. -- Grant Edwards grant.b.edwardsYow! I have the power to at HALT PRODUCTION on all gmail.comTEENAGE SEX COMEDIES!! -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Tue, 25 Feb 2014 02:18:43 -, Dennis Lee Bieber wlfr...@ix.netcom.com wrote: On Mon, 24 Feb 2014 01:01:15 -, Rhodri James rho...@wildebst.org.uk declaimed the following: The function range returns the sequence of numbers 1, 2, 3, 4 and 5 [*], so this has the same effect as if you had typed: Wrong -- it returns the sequence 0, 1, 2, 3, 4... Duh, yes. I do know better than that... -- Rhodri James *-* Wildebeest Herder to the Masses -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 26/02/2014 02:06, Cameron Simpson wrote: On 24Feb2014 13:59, Mark Lawrence breamore...@yahoo.co.uk wrote: On 24/02/2014 04:01, ru...@yahoo.com wrote: On 02/23/2014 08:21 PM, Mark Lawrence wrote: On 24/02/2014 02:55, Benjamin Kaplan wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. I'm reading gmane.comp.python.general using Thunderbird 24.3.0 on Windows 7. The original message was properly indented on Google Groups. Perhaps you should switch to GG or some non-broken client that doesn't mangle whitespace. MRAB has confirmed that as always Thunderbird is working perfectly, thank you. He confirmed it worked for him. And yet your copy rendered incorrectly. MRAB pointed at a possible cause (mixed TABs and spaces). But you can stick with your bug ridden, badly flawed tool as long as you like, just expect me to keep complaining until google fixes it, or people stop using it, or people follow the instructions that were put up on a Python web site to prevent the bugs showing up. Methinks rurpy's GG suggestion was bait aimed specificly at you. I recognised it as sarcasm (or parody?). Relax. Frankly I don't give a damn one way or the other, I'm simply cheesed off with seeing garbage coming through from gg, in the same way readers of this list are fed up with me complaining about it :) -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 02/25/2014 07:52 PM, Ethan Furman wrote: On 02/23/2014 08:01 PM, ru...@yahoo.com wrote: On 02/23/2014 08:21 PM, Mark Lawrence wrote: On 24/02/2014 02:55, Benjamin Kaplan wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. I'm reading gmane.comp.python.general using Thunderbird 24.3.0 on Windows 7. The original message was properly indented on Google Groups. Perhaps you should switch to GG or some non-broken client that doesn't mangle whitespace. LOL! How long have you waited to say that? ;) A while. It was worth the wait though. :-) -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 24Feb2014 13:59, Mark Lawrence breamore...@yahoo.co.uk wrote: On 24/02/2014 04:01, ru...@yahoo.com wrote: On 02/23/2014 08:21 PM, Mark Lawrence wrote: On 24/02/2014 02:55, Benjamin Kaplan wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. I'm reading gmane.comp.python.general using Thunderbird 24.3.0 on Windows 7. The original message was properly indented on Google Groups. Perhaps you should switch to GG or some non-broken client that doesn't mangle whitespace. MRAB has confirmed that as always Thunderbird is working perfectly, thank you. He confirmed it worked for him. And yet your copy rendered incorrectly. MRAB pointed at a possible cause (mixed TABs and spaces). But you can stick with your bug ridden, badly flawed tool as long as you like, just expect me to keep complaining until google fixes it, or people stop using it, or people follow the instructions that were put up on a Python web site to prevent the bugs showing up. Methinks rurpy's GG suggestion was bait aimed specificly at you. I recognised it as sarcasm (or parody?). Relax. -- Cameron Simpson c...@zip.com.au Scott Fansler wrote: Give me a break with this thread!! So what if another rider doesn't wave?? Who the hell cares!?!? I wave to other riders from my HD when the thought/moment is there. If they wave back cool, if not, so what. Maybe they didn't see me, maybe they're pissed at their boss or spouse or life in general and are out for a putt to clear out the BS and don't care to wave back. Big deal. Have you seen EVERY motorcyle that EVER rode past you going the other way?? Don't think so. Stop posing ride, wave or no wave. 2 cents Somebody get the pliers, this one's hooked deep. We'll need some more bait too. You might want to fiddle with drag setting on your reel too. - Tim Simpson t...@peop.tdsnet.com in rec.moto -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 23Feb2014 18:55, Benjamin Kaplan benjamin.kap...@case.edu wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. My copy was fine too. I'm reading it via the python-list mailing list, with mutt. -- Cameron Simpson c...@zip.com.au Deep into the monitor peering, long I sat there wond'ring, fearing, Doubting, while the disk kept churning, turning yet to churn some more. Save! I said, You cursed mother! Save my data from before! One thing did the phosphors answer, only this and nothing more, Just, Abort, Retry, Ignore? -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 02/23/2014 08:01 PM, ru...@yahoo.com wrote: On 02/23/2014 08:21 PM, Mark Lawrence wrote: On 24/02/2014 02:55, Benjamin Kaplan wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. I'm reading gmane.comp.python.general using Thunderbird 24.3.0 on Windows 7. The original message was properly indented on Google Groups. Perhaps you should switch to GG or some non-broken client that doesn't mangle whitespace. LOL! How long have you waited to say that? ;) -- ~Ethan -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Sunday, 23 February 2014 05:43:17 UTC, Scott W Dunning wrote: I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. Meaning is there a way I can call a function and then add *5 or something like that? The following answers your question but is probably not a method you want to employ. from functools import partial def a(ch): print(ch) def b(x): print(x + 10) [x() for x in [partial(a, 'd'), partial(b, 10)]*5] Produces d 14 d 14 d 14 d 14 d 14 --Simon -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Sunday, 23 February 2014 05:43:17 UTC, Scott W Dunning wrote: I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. Meaning is there a way I can call a function and then add *5 or something like that? The following answers your question but is probably not a method you want to employ. from functools import partial def a(ch): print(ch) def b(x): print(x + 4) [x() for x in [partial(a, 'd'), partial(b, 10)]*5] Produces d 14 d 14 d 14 d 14 d 14 --Simon -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 24/02/2014 04:01, ru...@yahoo.com wrote: On 02/23/2014 08:21 PM, Mark Lawrence wrote: On 24/02/2014 02:55, Benjamin Kaplan wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. I'm reading gmane.comp.python.general using Thunderbird 24.3.0 on Windows 7. The original message was properly indented on Google Groups. Perhaps you should switch to GG or some non-broken client that doesn't mangle whitespace. MRAB has confirmed that as always Thunderbird is working perfectly, thank you. But you can stick with your bug ridden, badly flawed tool as long as you like, just expect me to keep complaining until google fixes it, or people stop using it, or people follow the instructions that were put up on a Python web site to prevent the bugs showing up. -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
- Original Message - On Feb 23, 2014, at 1:44 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Sorry, I don't really understand your question. Could you show an example of what you are doing? Do you mean add 5 or *5? Add *5 doesn't really mean anything to me. Sorry I forgot to add the code that I had to give an example of what I was talking about. I’ll put it below, sorry that it’s so long. A Here's an example of how your star() function could be rewritten. Note that it does not exactly do what it does in your example regarding the start and end position of the turtle. So use it for inspiration only ;) from turtle import * from math import sin, sqrt, radians def star(width): R = (width)/(2*sin(radians(72))) A = (2*width)/(3+sqrt(5)) # record the initial position position = getturtle().pos() heading = getturtle().heading() penup() left(36) # initial angle forward(R) pendown() for arms in range(5): left(144) forward(A) right(72) forward(A) penup() # go back to the initial position getturtle().setpos(position) getturtle().setheading(heading) showturtle() clear() star(50) -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
Scott W Dunning swdunn...@cox.net writes: I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. You should ask question like this on the “python-tutor” forum. I say that because this question suggests you have yet to learn about basic Python features like loops. My recommendation is that you work your way thoroughly through the Python tutorial URL:http://docs.python.org/3/tutorial/, doing each example and experimenting to understand it before progressing. By the end, you will have a much more comprehensive grasp of the basics of Python, and have a toolkit of concepts and techniques for addressing questions like the above. Thanks for any help! Hope that helps! Feel free to ask for help on the Tutor forum URL:https://mail.python.org/mailman/listinfo/tutor. -- \ “We spend the first twelve months of our children's lives | `\ teaching them to walk and talk and the next twelve years | _o__) telling them to sit down and shut up.” —Phyllis Diller | Ben Finney -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Sat, 22 Feb 2014 22:43:17 -0700, Scott W Dunning wrote: Hello, I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. Meaning is there a way I can call a function and then add *5 or something like that? Sorry, I don't really understand your question. Could you show an example of what you are doing? Do you mean add 5 or *5? Add *5 doesn't really mean anything to me. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 23/02/2014 3:43 PM, Scott W Dunning wrote: I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. Meaning is there a way I can call a function and then add *5 or something like that? The same way you repeat anything in Python: with a loop construct. for _ in range(5): func() -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Sun, 23 Feb 2014 05:43:17 -, Scott W Dunning swdunn...@cox.net wrote: I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. Meaning is there a way I can call a function and then add *5 or something like that? The usual way to call a function several times is to use a loop, like this: for i in range(5): my_function() The function range returns the sequence of numbers 1, 2, 3, 4 and 5 [*], so this has the same effect as if you had typed: my_function() my_function() my_function() my_function() my_function() This isn't a great advantage if you just want to call the function two or three times, but when you want to call it two or three hundred times it matters a lot more! You can still use the same technique if you want to pass different parameters to the function each time you call it: for i in range(6): print(i*i) for day in (Mon, Tue, Wed, Thu, Fri): do_stuff_for_day(day) -- Rhodri James *-* Wildebeest Herder to the Masses -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 24/02/2014 00:55, alex23 wrote: On 23/02/2014 3:43 PM, Scott W Dunning wrote: I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. Meaning is there a way I can call a function and then add *5 or something like that? The same way you repeat anything in Python: with a loop construct. for _ in range(5): func() For the benefit of newbies, besides the obvious indentation error above, the underscore basically acts as a dummy variable. I'll let the language lawyers give a very detailed, precise description :) -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Feb 23, 2014, at 1:44 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Sorry, I don't really understand your question. Could you show an example of what you are doing? Do you mean add 5 or *5? Add *5 doesn't really mean anything to me. Sorry I forgot to add the code that I had to give an example of what I was talking about. I’ll put it below, sorry that it’s so long. A couple of people have basically answered my question though. I take it was I was talking about was a loop, which I haven’t learned in school yet but, it seems semi self-explanatory. As you can see I added a loop in there about half way down the code (i put it in bold) and it seemed to do what I want. Now I’m going to try and do what Rhodri suggested, a range function? I’m not sure exactly what that’ll do but I think it’ll clean up my code more and make things easier to call? from turtle import * from math import sin, sqrt, radians def star(width): R = (width)/(2*sin(radians(72))) A = (2*width)/(3+sqrt(5)) penup() left(18) penup() forward(R) pendown() left(162) forward(A) right(72) forward(A) left(144) forward(A) right(72) forward(A) left(144) forward(A) right(72) forward(A) left(144) forward(A) right(72) forward(A) left(144) forward(A) right(72) forward(A) penup() left(162) forward(R) left(162) showturtle() def fillstar(color): fillcolor(color) begin_fill() star(25) end_fill() red = red fillstar(red) def space(width): penup() forward(2*width) pendown() space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) def row(width): penup() right(90) forward(width) right(90) forward(11*width) right(180) pendown() row(25) for i in range (5): fillstar(red) space(25) row(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) row(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) row(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) row(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) row(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) row(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) row(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) fillstar(red) space(25) -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Feb 23, 2014, at 17:09, Mark Lawrence breamore...@yahoo.co.uk wrote: For the benefit of newbies, besides the obvious indentation error above, the underscore basically acts as a dummy variable. I'll let the language lawyers give a very detailed, precise description :) You mean a dummy name binding, right? If we say variable we might confuse those newly arrived pilgrims from other language kingdom. (If you squint hard, I think there's some facetious tags in there :) ) -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Feb 23, 2014, at 12:59 AM, Ben Finney ben+pyt...@benfinney.id.au wrote: You should ask question like this on the “python-tutor” forum. Thanks Ben, I wasn’t aware of PythonTutor. -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
I understood what you meant because I looked up loops in the python documentation since we haven’t got there yet in school. On Feb 23, 2014, at 6:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( -- https://mail.python.org/mailman/listinfo/python-list -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( -- Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 24/02/2014 02:55, Benjamin Kaplan wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( -- Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. I'm reading gmane.comp.python.general using Thunderbird 24.3.0 on Windows 7. -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 2014-02-24 03:21, Mark Lawrence wrote: On 24/02/2014 02:55, Benjamin Kaplan wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( -- Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. I'm reading gmane.comp.python.general using Thunderbird 24.3.0 on Windows 7. It looked OK to me (also using Thunderbird). However, examining the source, I can see that the first line is indented with 5 spaces and the second line with 1 tab. -- https://mail.python.org/mailman/listinfo/python-list
Re: Functions help
On 02/23/2014 08:21 PM, Mark Lawrence wrote: On 24/02/2014 02:55, Benjamin Kaplan wrote: On Sun, Feb 23, 2014 at 5:39 PM, alex23 wuwe...@gmail.com wrote: On 24/02/2014 11:09 AM, Mark Lawrence wrote: On 24/02/2014 00:55, alex23 wrote: for _ in range(5): func() the obvious indentation error above Stupid cutpaste :( Your message came through fine for me (viewing as mailing list in gmail). Mark's client must be dropping spaces. I'm reading gmane.comp.python.general using Thunderbird 24.3.0 on Windows 7. The original message was properly indented on Google Groups. Perhaps you should switch to GG or some non-broken client that doesn't mangle whitespace. -- https://mail.python.org/mailman/listinfo/python-list
Functions help
Hello, I had a question regarding functions. Is there a way to call a function multiple times without recalling it over and over. Meaning is there a way I can call a function and then add *5 or something like that? Thanks for any help! Scott -- https://mail.python.org/mailman/listinfo/python-list
Profiling very small/quick functions, help!?
i use this code to profile. however for small standard functions it just says 0 seconds. so one solution is to run the function a very big number of times(how big?). but the bottom code doesnt work, it just runs the same profiling 1 times insetad of running the fucntion 10K times and evaluate the time of all thsoe 10K times. ao how to solve this? if __name__==__main__: try: from cProfile import run except: from profile import run run(tests()) if __name__==__main__: try: from cProfile import run except: from profile import run for x in range(1, 1): run(power(10,10)) -- http://mail.python.org/mailman/listinfo/python-list
Re: Profiling very small/quick functions, help!?
On Apr 16, 12:35 pm, [EMAIL PROTECTED] wrote: if __name__==__main__: try: from cProfile import run except: from profile import run for x in range(1, 1): run(power(10,10)) def test1(): for x in xrange(1,1): test = power(10,10) if __name__==__main__: try: from cProfile import run except: from profile import run for x in range(1, 1): run(test1()) all the best! -- Aaron Watters === http://www.xfeedme.com/nucular/pydistro.py/go?FREETEXT=jar -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sun, 23 Sep 2007 18:32:28 -0700, Kay Schluehr wrote: On 22 Sep., 02:14, Bruno Desthuilliers [EMAIL PROTECTED] wrote: Kay Schluehr a crit : (snip) I checked out Io once and I disliked it. I expected Io's prototype OO being just a more flexible variant of class based OO but Io couples a prototype very closely to its offspring. When A produces B and A.f is modified after production of B also B.f is modified. A controls the state of B during the whole lifetime of B. I think parents shall not do this, not in real life and also not in programming language semantics. I may totally miss the point, but how is this different from: class A(object): def dothis(self): print A.dothis(%s) % self class B(A): pass b = B() b.dothis() def dothat(self): print function dothat(%s) % self A.dothis = dothat b.dothis() It's not a big deal because you do not use a class to propagate mutable state unless you are using a class attribute intentionally ( i guess you do not overuse it just to avoid object encapsulation and make everything global ). When using a prototype as in Io you need to protect the state of the child object yourself. Just like in Python! Here `things` are shared between all children: class A(object): things = list() def add(self, thing): self.things.append(thing) This is what happens too when you use this Io snippet: A := Object clone do( things := list() add := method(thing, self things append(thing) ) ) If you don't want `things` to be shared you write an `init` method, in both Python and Io. Python: class B(object): def __init__(self): self.things = list() def add(self, thing): self.things.append(thing) And Io: B := Object clone do( init := method( self things := list() self ) add := method(thing, self things append(thing) ) ) The `init` is called by the default `clone` method automatically just like `__init__()` in Python. It is really much like the class/instance relationship in Python with just the line between class and instance blurred. You can do this by overwriting the objects slots but then you end up writing your own object constructors and the templates accordingly, also named classes by some. Not having dedicated object constructors, member variable initializations and the presumed class definition boilerplate comes at the price of introducing them on your own. The mechanism is already there in Io, no need to invent, just use it. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
In message [EMAIL PROTECTED], Bryan Olson wrote: The keyword lambda sucks. ... Alonzo Church's calculus used the *symbol*. The keyword was popularized by LISP, and hence adopted by most other languages to copy the concept. In my view, it's no worse than using = for assignment instead of equality. function would be a much better keyword. As used that way in JavaScript. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
In message [EMAIL PROTECTED], Cristian wrote: I think it would make more sense to have beginners _know_ that functions are like all other variables ... Functions are not variables. Though they are values, and can be held in variables. In Python, every name is a variable, and can be assigned to. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
In message [EMAIL PROTECTED],
[EMAIL PROTECTED] wrote:
A question: if you WERE to implement function definitions as normal
expressions, how would you go about embedding it within an expression?
x = map(def a:
line of code
line of code
line of code
, [1, 2, 3])
Perl can do it just fine:
$x = map
(
sub
{
...
},
[1, 2, 3]
);
The fact that Python has difficulties is purely a demonstration of the
limitations of indentation-controlled syntax, not a criticism of the
concept itself.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Lawrence D'Oliveiro [EMAIL PROTECTED] writes: The fact that Python has difficulties is purely a demonstration of the limitations of indentation-controlled syntax, not a criticism of the concept itself. Not even. Haskell has indentation syntax (they call it layout) but can have multi-line function definitions inside expressions. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian a écrit :
On Sep 21, 5:21 pm, Bruno Desthuilliers
[EMAIL PROTECTED] wrote:
Ok, then what about classes ? They also are objects-like-any-other,
after all. So should we have this syntax too ?
MyClass = class(ParentClass):
__init__ = function (self, name):
self.name = name
?-)
For consistency I would suggest this, but Python already does this!
Foo = type('Foo', (object, ), {'bar': lambda self, bar: bar})
I've created a new class and then binded it to name afterwards. If you
can import modules without special syntax and you can create classes
without special syntax, why should functions be treated any
differently?
You already can create functions without using the def statement:
Help on class function in module __builtin__:
class function(object)
| function(code, globals[, name[, argdefs[, closure]]])
|
| Create a function object from a code object and a dictionary.
| The optional name string overrides the name from the code object.
| The optional argdefs tuple specifies the default argument values.
| The optional closure tuple supplies the bindings for free variables.
|
HTH
--
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Re: Would Anonymous Functions Help in Learning Programming/Python?
On Mon, 24 Sep 2007 11:43:59 +0200, Bruno Desthuilliers wrote: You already can create functions without using the def statement: Help on class function in module __builtin__: class function(object) | function(code, globals[, name[, argdefs[, closure]]]) | | Create a function object from a code object and a dictionary. | The optional name string overrides the name from the code object. | The optional argdefs tuple specifies the default argument values. | The optional closure tuple supplies the bindings for free variables. | Where the heck does *this* come from? Neither Python 2.5.1 nor the 3.0alpha has this in `__builtin__`. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Mon, 2007-09-24 at 10:05 +, Marc 'BlackJack' Rintsch wrote: On Mon, 24 Sep 2007 11:43:59 +0200, Bruno Desthuilliers wrote: You already can create functions without using the def statement: Help on class function in module __builtin__: class function(object) | function(code, globals[, name[, argdefs[, closure]]]) | | Create a function object from a code object and a dictionary. | The optional name string overrides the name from the code object. | The optional argdefs tuple specifies the default argument values. | The optional closure tuple supplies the bindings for free variables. | Where the heck does *this* come from? Neither Python 2.5.1 nor the 3.0alpha has this in `__builtin__`. It comes from the 'new' module: import new help(new.function) Help on class function in module __builtin__: ... Oddly enough, the help misrepresents which module the function is coming from. -- Carsten Haese http://informixdb.sourceforge.net -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 24, 9:09 am, Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: Python: class B(object): def __init__(self): self.things = list() def add(self, thing): self.things.append(thing) And Io: B := Object clone do( init := method( self things := list() self ) add := method(thing, self things append(thing) ) ) The `init` is called by the default `clone` method automatically just like `__init__()` in Python. It is really much like the class/instance relationship in Python with just the line between class and instance blurred. [...] Ciao, Marc 'BlackJack' Rintsch O.K. Marc, I'm convinced by the examples you presented. So init is also special in Io and is called at the clone event to fill object slots with data. Now I have to track back in the discussion thread to remember why we started to talk about Io... -- http://mail.python.org/mailman/listinfo/python-list
RE: Would Anonymous Functions Help in Learning Programming/Python?
Carsten Haese wrote: Where the heck does *this* come from? Neither Python 2.5.1 nor the 3.0alpha has this in `__builtin__`. It comes from the 'new' module: import new help(new.function) Help on class function in module __builtin__: ... Oddly enough, the help misrepresents which module the function is coming from. Not exactly: help(type(lambda x: x)) Help on class function in module __builtin__: The function type is builtin, but it doesn't have an exposed name. `new.function` is simply a name bound to the function type. Note the help says *class* function ... Tim Delaney -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Carsten Haese [EMAIL PROTECTED] wrote: It comes from the 'new' module: import new help(new.function) Help on class function in module __builtin__: ... Oddly enough, the help misrepresents which module the function is coming from. No, I don't think it is misrepresenting anything. The 'new' module simply exposes names for some things which don't otherwise have names, none of the types accessible through that module are actually defined there. The class 'function' is a builtin definition, but by default it isn't bound to any name accessible to the Python interpreter. If you do: def f(): pass type(f).__module__ '__builtin__' help(type(f)) Help on class function in module __builtin__: ... etc ... then the help makes a bit more sense. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Steven D'Aprano a écrit : On Fri, 21 Sep 2007 22:07:55 +, Cristian wrote: True, there is lambda, but that is very limited. It might be useful for key arguments, but not much else. No, lambda is useful for anything that any other function is useful for, provided that you can write it as a single expression and not need to use statements. Which makes a great difference in practice !-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Matthew Woodcraft a écrit : Cristian [EMAIL PROTECTED] wrote: To me, the biggest setback for new programmers is the different syntax Python has for creating functions. Instead of the common (and easy to grasp) syntax of foo = bar Python has the def foo(): syntax. [...] in a program like Python there doesn't seem to be any other reason to have it. One reason for the different syntax is that functions, unlike most other objects, know their own names (which can be shown in tracebacks and the like). Nope. They know *one* of their names - the one they've been given when first instanciated. Which may or not be the name used to get at them... -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 24, 9:16 pm, Bruno Desthuilliers bruno. [EMAIL PROTECTED] wrote: Matthew Woodcraft a écrit : One reason for the different syntax is that functions, unlike most other objects, know their own names (which can be shown in tracebacks and the like). Nope. They know *one* of their names - the one they've been given when first instanciated. Which may or not be the name used to get at them... That's exactly the point - a function may be given many names through the assignment statement, just like any other data value. However, the *first* name given to a function (the one in the def statement) is special, as that is the name the function knows *itself* by. While a function *can* be treated like any other piece of data once you have a reference to one, the original statement does a lot more than a normal assignment does: - being within the scope of a function significantly alters name binding and lookup - return statements and yield statements are meaningful only within the scope of a function - you can attach decorators to a function definition - you can include a docstring in a function definition For the original poster, I suggest trying some of the other suggestions in this thread, where you skip the def statement and instead look at manipulating standard library functions like math.sin and math.cos. Using a dictionary to select a function to run may be a good trick to illustrate the usefulness of this technique (e.g. passing in a command line argument to choose a function to call to generate a test sequence) -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
NickC a écrit : On Sep 24, 9:16 pm, Bruno Desthuilliers bruno. [EMAIL PROTECTED] wrote: Matthew Woodcraft a écrit : One reason for the different syntax is that functions, unlike most other objects, know their own names (which can be shown in tracebacks and the like). Nope. They know *one* of their names - the one they've been given when first instanciated. Which may or not be the name used to get at them... That's exactly the point - a function may be given many names through the assignment statement, just like any other data value. However, the *first* name given to a function (the one in the def statement) is special, as that is the name the function knows *itself* by. knows itself by ? Really ?-) def toto(level): ... print toto %s % level ... if level == 0: print done ... else: toto(level-1) ... toto(3) toto 3 toto 2 toto 1 toto 0 done tutu = toto def toto(level): ... print YADDA YADDA ... tutu(3) toto 3 YADDA YADDA While a function *can* be treated like any other piece of data once you have a reference to one, the original statement does a lot more than a normal assignment does: Indeed. But : - being within the scope of a function significantly alters name binding and lookup Runtime stuff and 'locals' parameters of te function object initializer AFAICT. - return statements and yield statements are meaningful only within the scope of a function s/within the scope/in the code object/, I'd say... Look at the signature of the function object's initializer, it takes a code object. Please some guru correct me if I'm wrong, but AFAICT, you can have all this working without the def statement itself (even if it's quite enough of a boring work to justify the existence of the def statement). Anyway, the OP suggestion was to turn the statement into an expression (à la javascript), not to get rid of it. - you can attach decorators to a function definition @decorators are just syntactic sugar for HOFs. If you want to apply a decorator do a lambda, you don't need this syntax - just pass the lambda as a param to the decorator. - you can include a docstring in a function definition And you can add it afterwards too: toto.__doc__ is None True toto.__doc__ = yadda toto.__doc__ 'yadda' Don't get me wrong, I'm not saying the def statement is useless. Just that the reasons why this statement exists have very few to do with your arguments here. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On 22 Sep., 23:17, Erik Max Francis [EMAIL PROTECTED] wrote: The attribute and method (not made distinct in Io; they're called slots) is much the same as with Python; the current instance is checked for the object, then its parents, then _its_ parents, and so on. Repeating the same point as Marc doesn't mean that I have to repeat my reply as well. Doesn't it? -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Scott David Daniels wrote: Ron Adam wrote: Scott David Daniels wrote: Cristian wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. Here's an idea: import math def sin_integral(start, finish, dx): ... def cos_integral(start, finish, dx): ... generalize and separate the integration technique from the function it integrates. How about this? It's based on the apple basic program example in How to Enjoy Calculus. Ron import math def integrate(fn, x1, x2, n=100):... def fn(x): ... print Area of fn:, integrate(fn, 0, 2) print Area of cos fn:, integrate(math.cos, 1, 2) The point was a pedagogic suggestion, i.e. I understood your point. I just found it interesting since I've been trying to extend my math (for use with python) skills in this area. Try taking your friend along this path. I wasn't trying to do a particularly good job integrating, simply trying to show how you could motivate first-class functions by showing a useful and fun (at least to an engineer) function that cries out for higher order functions. In my experience engineers often want a reason its useful before engaging with an idea. I'll bet that after a few such experiences he'll see how passing around functions and (later) making functions from from functions is a great tool to have in his toolbox. Once he sees that, there will be no problem. Yes, I agree. Another useful thing I've found is to store functions in a dictionary and call them (dispatching) based on some data value. Ron -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Ron Adam wrote: Scott David Daniels wrote: Ron Adam wrote: How about this? def integrate(fn, x1, x2, n=100):... The point was a pedagogic suggestion, ... I understood your point. I just found it interesting since I've been trying to extend my math (for use with python) skills in this area. Ah, sorry. I had realized I wasn't explicit in my first message. Yes, a perfectly fine integration. You can then (and this is a major jump to get used to): import functools Sine = functools.partial(integrate, math.cos, 0.0, n=100) Similarly, you can define a derivative that will behave fairly well, all without examining the definition of the function being operated upon. -Scott -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian a écrit : (snip) To me, the biggest setback for new programmers is the different syntax Python has for creating functions. Instead of the common (and easy to grasp) syntax of foo = bar It's actually a mostly *un*common syntax when it comes to functions. The only mainstream language I know allowing such a syntax is javascript. Now given python's parsing rules, I wonder how this could be implemented... Python has the def foo(): syntax. So, when a new programmer is first introduced to functions they are immediately confronted with the notion that functions are different. Which is the case in most non functional languages. After all, they have their own special syntax. This seems to only further the separation newbies make between data and functions or stuff and actions. Now, the vast majority of us learned this dichotomy when we first began to program, so we are ingrained to assume and even expect a different syntax for function declaration, but in a program like Python there doesn't seem to be any other reason to have it. Technically, I'd say patsing rules. From a more conceptual POV, Python was meant to be the missing link between shell scripts and C - and some design choices clearly (IMHO) came from the desire to look familiar enough to C programmers. Even if Python ended up with some (restricted) support for functional programming, it's still has it's roots in procedural programming. Furthermore, I think it actually inhibits the learning of the uninitiated. We can, of course, keep the current syntax as sugar. To someone who's learning to program wouldn't a syntax like the further give them all they need and also reinforces the idea that functions are data just like everything else? Python's functions are *objects* like anything else. And objects are more than data. My 2 cents: show your friend that Python's functions are objects, and that other objects can be callable too... my_function = function(foo, bar): pass an_instance_method = function(self, foo): pass a_method_declaration = method(self, foo): pass The last one is mostly my pet peeve of having Python magically create methods out of (what is essentially) a function declaration. There's not much magic in this. What's stored as an attribute of the class *is* a function. It's only wrapped in a method object when looked up. And FWIW, it's the function object itself that takes care of this, thanks to the descriptor protocol (all relevant doc is on python.org). When I first learned it, it felt wrong but you had to press through it because there was really no other way of declaring methods. Truth is that you do *not* declare methods in Python. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Kay Schluehr a écrit : (snip) I checked out Io once and I disliked it. I expected Io's prototype OO being just a more flexible variant of class based OO but Io couples a prototype very closely to its offspring. When A produces B and A.f is modified after production of B also B.f is modified. A controls the state of B during the whole lifetime of B. I think parents shall not do this, not in real life and also not in programming language semantics. I may totally miss the point, but how is this different from: class A(object): def dothis(self): print A.dothis(%s) % self class B(A): pass b = B() b.dothis() def dothat(self): print function dothat(%s) % self A.dothis = dothat b.dothis() -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Kay Schluehr a écrit : On 22 Sep., 23:17, Erik Max Francis [EMAIL PROTECTED] wrote: The attribute and method (not made distinct in Io; they're called slots) is much the same as with Python; the current instance is checked for the object, then its parents, then _its_ parents, and so on. Repeating the same point as Marc doesn't mean that I have to repeat my reply as well. Doesn't it? Then please don't answer my own repeating of the same point !-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian a écrit : On Sep 21, 4:47 pm, Sean Tierney [EMAIL PROTECTED] wrote: Just tell him that functions are like all other variables and can therefore be passed by other functions or returned by other functions. I could Just tell him that functions are like all other variables and can therefore be passed by other functions or returned by other functions. but wouldn't it be great if Python did this for me? It seems to me that the ability for Python to explicitly state that functions-are- like-other-variables is there so why not expose it? Ok, then what about classes ? They also are objects-like-any-other, after all. So should we have this syntax too ? MyClass = class(ParentClass): __init__ = function (self, name): self.name = name ?-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Scott David Daniels wrote: Ron Adam wrote: Scott David Daniels wrote: Ron Adam wrote: How about this? def integrate(fn, x1, x2, n=100):... The point was a pedagogic suggestion, ... I understood your point. I just found it interesting since I've been trying to extend my math (for use with python) skills in this area. Ah, sorry. I had realized I wasn't explicit in my first message. Yes, I wasn't trying to correct you. I'm sorry if it came across that way. Yes, a perfectly fine integration. There's still something about it that bothers me. I think it may be the n=100 rather than delta='.0001', or some other way to specify the minimal error. (Yes, it's a bit off topic.) You can then (and this is a major jump to get used to): import functools Sine = functools.partial(integrate, math.cos, 0.0, n=100) I haven't played around with .partial yet. I wonder if it could be used in dispatching situations where the function signatures differ? Similarly, you can define a derivative that will behave fairly well, all without examining the definition of the function being operated upon. I'll get around to doing that at some point. ;-) I also have a class that solves equations that takes a function in a similar way. It uses the same method used by HP calculators to solve TVM equations. Cheers, Ron -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On 22 Sep., 02:14, Bruno Desthuilliers [EMAIL PROTECTED] wrote: Kay Schluehr a écrit : (snip) I checked out Io once and I disliked it. I expected Io's prototype OO being just a more flexible variant of class based OO but Io couples a prototype very closely to its offspring. When A produces B and A.f is modified after production of B also B.f is modified. A controls the state of B during the whole lifetime of B. I think parents shall not do this, not in real life and also not in programming language semantics. I may totally miss the point, but how is this different from: class A(object): def dothis(self): print A.dothis(%s) % self class B(A): pass b = B() b.dothis() def dothat(self): print function dothat(%s) % self A.dothis = dothat b.dothis() It's not a big deal because you do not use a class to propagate mutable state unless you are using a class attribute intentionally ( i guess you do not overuse it just to avoid object encapsulation and make everything global ). When using a prototype as in Io you need to protect the state of the child object yourself. You can do this by overwriting the objects slots but then you end up writing your own object constructors and the templates accordingly, also named classes by some. Not having dedicated object constructors, member variable initializations and the presumed class definition boilerplate comes at the price of introducing them on your own. Prototypes have a purpose of course when you want to transfer state to a newly created object. Using a prototyping mechanism as a generic form of a copy constructor is the right kind to thinking about them IMO. I have got the impression that the discussion has drifted away from what Paul Rubin suggested, namely abandone the expression/statement distinction. Instead we are discussing the advantages and disadvantages of object models now. Can we stop here, please? -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 21, 5:21 pm, Bruno Desthuilliers
[EMAIL PROTECTED] wrote:
Ok, then what about classes ? They also are objects-like-any-other,
after all. So should we have this syntax too ?
MyClass = class(ParentClass):
__init__ = function (self, name):
self.name = name
?-)
For consistency I would suggest this, but Python already does this!
Foo = type('Foo', (object, ), {'bar': lambda self, bar: bar})
I've created a new class and then binded it to name afterwards. If you
can import modules without special syntax and you can create classes
without special syntax, why should functions be treated any
differently?
--
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Re: Would Anonymous Functions Help in Learning Programming/Python?
On Fri, 21 Sep 2007 19:52:41 -0400, Carl Banks wrote: First of all, let me say that I think functions as first class data is helpful, but not crucial, to programming in Python, and there are many people who simply don't need the lesson. Especially someone like an engineer (in the classical sense), who isn't building versatile software packages, won't need to resort to functional programming much. Of course you don't *need* functional programming as in there's no way around it, but why are engineers such an exception!? I find the stuff in `itertools` very handy when it comes to filter, manipulate, group and aggregate data from large log files in ad hoc scripts. I'm not an engineer but I guess there are similar tasks with log files or measurement results. For straightforward tasks, like sorting lists with a custom ordering, functional progamming merely a convenience, and can be done without. ``for`` loops are just a convenience, you can do without. ;-) Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Carl Banks [EMAIL PROTECTED] writes: Especially someone like an engineer (in the classical sense), who isn't building versatile software packages, won't need to resort to functional programming much. http://www.math.chalmers.se/~rjmh/Papers/whyfp.html -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On 22 Sep., 00:36, Cristian [EMAIL PROTECTED] wrote: Yeah, I agree, that does look pretty ugly. Correct me if I'm wrong, but I thought the way Python determines a block is by the whitespace of the first line. So, as long as the spacing (or !tabbing!) is consistent from line to line the parser will know it's part of the same block. From that I don't think the parser would have much trouble extracting the function definition from the above example. I would change the word def. That's never been informative enough for me. Here is the grammar: http://svn.python.org/projects/stackless/tags/python-2.5/Grammar/Grammar If you feel you can transform it into another unambigous grammar mixing statements and expressions it's up to you. Guido at least does not seem to show interest: http://www.artima.com/weblogs/viewpost.jsp?thread=147358 When you are working on it you'll need a parser generator that also checks your changes. EasyExtend might help http://www.fiber-space.de/EasyExtend/doc/EE.html You can use it with Python 2.5, create a new fiber and a Grammar.ext file. Note that the parser generator is LL(1) so it is not all powerfull but *very* efficient. Tokenization is performed separately. INDENT, DEDENT are indentation token used within the definition of the suite nonterminal. I'd provide additional help when you get stuck. Finally the standard response to your claims: this is all open source. This advice might be annoying and uncomfortable and maybe you just want to talk about some problems and make a few guesses instead of solving them actually. We are all Web 2.0 now and discussing issues and doing socialization might be more important than everything else even among geeks. This can be confusing however for people who believe that softskills are not everything. Regards, Kay -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Kay Schluehr [EMAIL PROTECTED] writes: If you feel you can transform it into another unambigous grammar mixing statements and expressions it's up to you. We got rid of the print statement for python 3.0. Why not get rid of the rest of them too? Just use expressions for everything, as works fine for plenty of other languages. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Scott David Daniels wrote: Cristian wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. Here's an idea: import math def sin_integral(start, finish, dx): total = 0.0 y0 = math.sin(start) for n in range(1, 1 + int((finish - start) / float(dx))): y1 = math.sin(start + n * dx) total += (y0 + y1) y0 = y1 return total / 2. * dx def cos_integral(start, finish, dx): total = 0.0 y0 = math.sin(start) for n in range(1, 1 + int((finish - start) / float(dx))): y1 = math.cos(start + n * dx) total += (y0 + y1) y0 = y1 return total / 2. * dx generalize and separate the integration technique from the function it integrates. How about this? It's based on the apple basic program example in How to Enjoy Calculus. Ron import math def integrate(fn, x1, x2, n=100): # Calculate area of fn using Simpson's rule. width = float(x2 - x1) / n area = fn(x1) if n % 2 != 0: # make sure its even n += 1 for n in range(1, n): x = x1 + n * width if n % 2 == 0: area += 2.0 * fn(x) else: area += 4.0 * fn(x) area += fn(x2) return area * (width / 3.0) def fn(x): return x**2 print Area of fn:, integrate(fn, 0, 2) print Area of cos fn:, integrate(math.cos, 1, 2) print Area of sin fn:, integrate(math.sin, 1, 2) Area of fn: 2.667 Area of cos fn: 0.0678264420216 Area of sin fn: 0.956449142468 -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On 22 Sep., 08:56, Paul Rubin http://[EMAIL PROTECTED] wrote: Kay Schluehr [EMAIL PROTECTED] writes: If you feel you can transform it into another unambigous grammar mixing statements and expressions it's up to you. We got rid of the print statement for python 3.0. Why not get rid of the rest of them too? Just use expressions for everything, as works fine for plenty of other languages. One might create a new dynamic functional+OO programming language, where small statements like print, assert, raise etc. all become functions and statements like while, for, with etc. become anonymous closures. I think Logix had gone once in this direction but was abandoned due to severe technical problems. So one might eventually revive this project with another more sound technical base. Personally I'm not sure it's worth a large effort and whether EasyExtend is the right toolkit at hand. So it's definitely not Guido who will revive it and also not me. Maybe some PyPy guys? What are we talking about - really? -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sat, 22 Sep 2007 00:47:37 -0700, Kay Schluehr wrote: On 22 Sep., 08:56, Paul Rubin http://[EMAIL PROTECTED] wrote: Kay Schluehr [EMAIL PROTECTED] writes: If you feel you can transform it into another unambigous grammar mixing statements and expressions it's up to you. We got rid of the print statement for python 3.0. Why not get rid of the rest of them too? Just use expressions for everything, as works fine for plenty of other languages. One might create a new dynamic functional+OO programming language, where small statements like print, assert, raise etc. all become functions and statements like while, for, with etc. become anonymous closures. Before someone starts to create such a thing he should take a look at Io which has just objects and methods. http://www.iolanguage.com/ Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Fri, 21 Sep 2007 23:38:38 -0700, Paul Rubin wrote: Carl Banks [EMAIL PROTECTED] writes: Especially someone like an engineer (in the classical sense), who isn't building versatile software packages, won't need to resort to functional programming much. http://www.math.chalmers.se/~rjmh/Papers/whyfp.html From the link: Abstract As software... That's it, lost me already. You ever see the kinds of programs mechanical engineers write? It isn't software. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Carl Banks [EMAIL PROTECTED] writes: That's it, lost me already. You ever see the kinds of programs mechanical engineers write? It isn't software. They do a lot of number crunching. Certainly they can appreciate higher order functions like integrate(f, x0, x1) to integrate the function f from x0 to x1; or diff(f, x0) to find the derivative of f at x0; etc. Fortran had cheesy ways to do this as far back as the 1950's. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 22, 10:40 am, Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: On Sat, 22 Sep 2007 00:47:37 -0700, Kay Schluehr wrote: On 22 Sep., 08:56, Paul Rubin http://[EMAIL PROTECTED] wrote: Kay Schluehr [EMAIL PROTECTED] writes: If you feel you can transform it into another unambigous grammar mixing statements and expressions it's up to you. We got rid of the print statement for python 3.0. Why not get rid of the rest of them too? Just use expressions for everything, as works fine for plenty of other languages. One might create a new dynamic functional+OO programming language, where small statements like print, assert, raise etc. all become functions and statements like while, for, with etc. become anonymous closures. Before someone starts to create such a thing he should take a look at Io which has just objects and methods. http://www.iolanguage.com/ Ciao, Marc 'BlackJack' Rintsch I checked out Io once and I disliked it. I expected Io's prototype OO being just a more flexible variant of class based OO but Io couples a prototype very closely to its offspring. When A produces B and A.f is modified after production of B also B.f is modified. A controls the state of B during the whole lifetime of B. I think parents shall not do this, not in real life and also not in programming language semantics. There was another, similar and also abandoned project a while ago heading for prototype OO called Prothon: http://mail.python.org/pipermail/python-announce-list/2004-March/002966.html When I remember correctly it was killed not because it was too ambitious but the author lost his vision and didn't want to grow Prothons ecosystem. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sat, 22 Sep 2007 02:44:35 -0700, Kay Schluehr wrote: I checked out Io once and I disliked it. I expected Io's prototype OO being just a more flexible variant of class based OO but Io couples a prototype very closely to its offspring. When A produces B and A.f is modified after production of B also B.f is modified. A controls the state of B during the whole lifetime of B. I think parents shall not do this, not in real life and also not in programming language semantics. Well it's like Python: inherited slots (attributes) are looked up in the ancestors. It should be easy to override `Object clone` in Io, so all slots of the ancestor are shallow copied to the clone, but I guess this might break existing code. At least for your own code you could introduce a `realClone` slot. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sat, 22 Sep 2007 02:32:30 -0700, Paul Rubin wrote: Carl Banks [EMAIL PROTECTED] writes: That's it, lost me already. You ever see the kinds of programs mechanical engineers write? It isn't software. They do a lot of number crunching. Certainly they can appreciate higher order functions like integrate(f, x0, x1) to integrate the function f from x0 to x1; or diff(f, x0) to find the derivative of f at x0; etc. Fortran had cheesy ways to do this as far back as the 1950's. Well, I appreaciate it, as do many other engineers, but for a lot of engineers functional programming might as well not exist, either because they don't about it or don't care about it. And it doesn't really affect them much, other than making them slightly less efficient then they could have been. That's the key here. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 22, 1:15 pm, Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: On Sat, 22 Sep 2007 02:44:35 -0700, Kay Schluehr wrote: I checked out Io once and I disliked it. I expected Io's prototype OO being just a more flexible variant of class based OO but Io couples a prototype very closely to its offspring. When A produces B and A.f is modified after production of B also B.f is modified. A controls the state of B during the whole lifetime of B. I think parents shall not do this, not in real life and also not in programming language semantics. Well it's like Python: inherited slots (attributes) are looked up in the ancestors. It should be easy to override `Object clone` in Io, so all slots of the ancestor are shallow copied to the clone, but I guess this might break existing code. At least for your own code you could introduce a `realClone` slot. Ciao, Marc 'BlackJack' Rintsch But in class based OO most relevant attributes are defined during object construction and they can't be simply changed by setting a class attribute. Later you often create new attributes as but on object level. You do not overuse the object/class relationship to broadcast changes to all objects. While you might override 'Object clone' I don't believe changing the way how the whole object model works is a good idea and since it happens on source level you will get also a performance hit. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Ron Adam wrote: Scott David Daniels wrote: Cristian wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. Here's an idea: import math def sin_integral(start, finish, dx): ... def cos_integral(start, finish, dx): ... generalize and separate the integration technique from the function it integrates. How about this? It's based on the apple basic program example in How to Enjoy Calculus. Ron import math def integrate(fn, x1, x2, n=100):... def fn(x): ... print Area of fn:, integrate(fn, 0, 2) print Area of cos fn:, integrate(math.cos, 1, 2) The point was a pedagogic suggestion, i.e. Try taking your friend along this path. I wasn't trying to do a particularly good job integrating, simply trying to show how you could motivate first-class functions by showing a useful and fun (at least to an engineer) function that cries out for higher order functions. In my experience engineers often want a reason its useful before engaging with an idea. I'll bet that after a few such experiences he'll see how passing around functions and (later) making functions from from functions is a great tool to have in his toolbox. Once he sees that, there will be no problem. -Scott David Daniels [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sat, 22 Sep 2007 06:58:57 -0700, Kay Schluehr wrote: On Sep 22, 1:15 pm, Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: On Sat, 22 Sep 2007 02:44:35 -0700, Kay Schluehr wrote: I checked out Io once and I disliked it. I expected Io's prototype OO being just a more flexible variant of class based OO but Io couples a prototype very closely to its offspring. When A produces B and A.f is modified after production of B also B.f is modified. A controls the state of B during the whole lifetime of B. I think parents shall not do this, not in real life and also not in programming language semantics. Well it's like Python: inherited slots (attributes) are looked up in the ancestors. It should be easy to override `Object clone` in Io, so all slots of the ancestor are shallow copied to the clone, but I guess this might break existing code. At least for your own code you could introduce a `realClone` slot. But in class based OO most relevant attributes are defined during object construction and they can't be simply changed by setting a class attribute. Later you often create new attributes as but on object level. You do not overuse the object/class relationship to broadcast changes to all objects. You don't do this in Io either. It's really like Python in this respect. There's an `init` slot that gets called by (the default) `clone` and you set instance attributes there, for example mutables so they are not shared by all clones. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
[EMAIL PROTECTED] wrote: There are already anonymous functions in Python. lambda x, y, z: x + y + z is the same as: def _(x, y, z): return x + y + z They are the same only in special cases: The special identifier _ is used in the interactive interpreter to store the result of the last evaluation; it is stored in the __builtin__ module. When not in interactive mode, _ has no special meaning and is not defined. [Python Reference Manual; 2.3.2 Reserved classes of identifiers. http://docs.python.org/ref/id-classes.html] -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian [EMAIL PROTECTED] wrote: To me, the biggest setback for new programmers is the different syntax Python has for creating functions. Instead of the common (and easy to grasp) syntax of foo = bar Python has the def foo(): syntax. [...] in a program like Python there doesn't seem to be any other reason to have it. One reason for the different syntax is that functions, unlike most other objects, know their own names (which can be shown in tracebacks and the like). -M- -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Bryan Olson [EMAIL PROTECTED] writes: [EMAIL PROTECTED] wrote: There are already anonymous functions in Python. lambda x, y, z: x + y + z is the same as: def _(x, y, z): return x + y + z They are the same only in special cases: The special identifier _ is used in the interactive interpreter to store the result of the last evaluation... I'm not sure what Chris was really getting at, since among other things lambda:... is an expression while def... is a statement. But Python certainly has anonymous functions without lambda: def compose(f,g): def h(*a, **k): return f(g(*a, **k)) return h x = compose(math.sin, math.cos)(1.0) computes sin(cos(1.0)) where a function equivalent to lambda x: sin(cos(x)) is constructed and used without being bound to a symbol. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian wrote: [...] Specifically, he's having trouble thinking of functions as first order data (don't worry, I haven't confused him with such terminology yet). [...] And, after we finally get a hold of first order functions, we appreciate its incorporation into languages. It would be a shame if my friend just learns the motions and never incorporates first order functions into his programs. The terminology I've heard for this is that functions are first-class values. There's a minor name-collision on class, but people have heard first-class in other contexts, and it means the same thing here: no second-class status for such values. First order has other usages, some contradicting what you mean. First-order functions are exactly those that cannot take functions as arguments. It would be a shame if your friend never incorporates *higher order* functions. [http://en.wikipedia.org/wiki/Higher-order_function] [...] my_function = function(foo, bar): pass an_instance_method = function(self, foo): pass a_method_declaration = method(self, foo): pass I just argued for adopting mainstream terminology, but here I like yours better. The keyword lambda sucks. All the other keywords, having been so carefully chosen to relate to their conversational usage, have mis-trained to look at this spelling-out of the name of an arbitrary symbol. Alonzo Church's calculus used the *symbol*. He just needed it to be distinct. Could as well have been the '$-calculus'. Function-as-value is not a trivial concept. I remember wrestling with it, and I've seen many others do the same. The 'lambda' keyword is so awful as to pass for deep mystery long after students have grasped first-class functions. function would be a much better keyword. Or follow ML and abbreviate to fn, or choose another term that clues one in to the meaning. I'd have caught on much quicker given a a hint to read: lambda x, y: x + y as: the function of two variables, call them x and y, that returns x + y. --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Paul Rubin wrote: Bryan Olson [EMAIL PROTECTED] writes: [EMAIL PROTECTED] wrote: There are already anonymous functions in Python. lambda x, y, z: x + y + z is the same as: def _(x, y, z): return x + y + z They are the same only in special cases: The special identifier _ is used in the interactive interpreter to store the result of the last evaluation... I'm not sure what Chris was really getting at, I was big-time unsure. At first, I thought Chris's latter form to be equivalent to a pass statement. I've long used the Python convention of assigning throw-away values to '_', and I was under the mistaken impression Python defined _ as a discard target. When I looked it up, I was surprised to find that my understanding of the _ variable was wrong, and shocked that there really is an interesting context where Chris's claim has a strong case. since among other things lambda:... is an expression while def... is a statement. True fact, but note that one form of statement is an expression. But Python certainly has anonymous functions without lambda: def compose(f,g): def h(*a, **k): return f(g(*a, **k)) return h x = compose(math.sin, math.cos)(1.0) computes sin(cos(1.0)) where a function equivalent to lambda x: sin(cos(x)) is constructed and used without being bound to a symbol. How anonymous is that function when we can see that its name is 'h'? import math f = compose(math.sin, math.cos) print f.__name__ Am I making a bogus argument? Kind of. Most authors of anonymous works do in fact have real names. The term really means that they entered the context at issue dissociated from their given name. Nevertheless, def is never a real anonymous function constructor. If our concern is Python's suitability for studying principles of programming, I think I'm on stronger ground. Python is great for getting things done. It is easy to learn in the sense of learning to to use if for practical tasks. Python's actual semantics are not as neat and clean as some other languages. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Bryan Olson [EMAIL PROTECTED] writes: How anonymous is that function when we can see that its name is 'h'? h is out of scope after compose returns, so the function is anonymous in the sense that there is no symbol bound to the function, through which you can refer to it. import math f = compose(math.sin, math.cos) print f.__name__ I prefer to think of __name__ as just some debugging info stuck inside the closure, though actually Python is introspective enough to be able to let you locate and call a function whose __name__ is h. Of course there might be more than one: f = compose(math.sin, math.cos) g = compose(math.sqrt, math.tan) print f.__name__, g.__name__ Nevertheless, def is never a real anonymous function constructor. Well, def constructs a function with a name, but the function can stay around after the name goes away, after which I'd say the function is nameless. One could otherwise say that (lambda x: x+x) is not anonymous either, since id(lambda ...) is a unique label stuck to it like a __name__. If our concern is Python's suitability for studying principles of programming, I think I'm on stronger ground. Python is great for getting things done. It is easy to learn in the sense of learning to to use if for practical tasks. Python's actual semantics are not as neat and clean as some other languages. Fair enough. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Kay Schluehr wrote: I checked out Io once and I disliked it. I expected Io's prototype OO being just a more flexible variant of class based OO but Io couples a prototype very closely to its offspring. When A produces B and A.f is modified after production of B also B.f is modified. A controls the state of B during the whole lifetime of B. I think parents shall not do this, not in real life and also not in programming language semantics. It sounds like you're talking about some language other than Io, or didn't delve deeply enough into it, since Io makes no such requirements. The attribute and method (not made distinct in Io; they're called slots) is much the same as with Python; the current instance is checked for the object, then its parents, then _its_ parents, and so on. -- Erik Max Francis [EMAIL PROTECTED] http://www.alcyone.com/max/ San Jose, CA, USA 37 20 N 121 53 W AIM, Y!M erikmaxfrancis No man quite believes in any other man. -- H.L. Mencken -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sat, 22 Sep 2007 14:09:13 -0700, Paul Rubin wrote: Nevertheless, def is never a real anonymous function constructor. Well, def constructs a function with a name, but the function can stay around after the name goes away, after which I'd say the function is nameless. One could otherwise say that (lambda x: x+x) is not anonymous either, since id(lambda ...) is a unique label stuck to it like a __name__. If you want to be tediously pedantic, lambda doesn't construct anonymous functions either: you can bind them to a name, and whether you do or not, they have a name. f = lambda: 3 f.__name__ 'lambda' It's just that all functions created by lambda share the same name. If you really want an anonymous function... def foo(): ... return 3 ... foo.__name__ = '' foo function at 0x97a26bc I know, I know, I'm being tediously pedantic... and that's not what the anonymity of lambda refers to. What it actually means is that the lambda doesn't create a name in a namespace. In that regard, calling a factory function is also anonymous, because the function isn't added to the calling code's namespace. Or, to put it another way... def factory(): def foo(): return 3 return foo Within factory(), foo() is not an anonymous function, because 'foo' is in the local namespace. But the result of factory() is anonymous in the same sense that lambda is: although the function object has a attribute __name__ set to 'foo', calling factory() doesn't modify the caller's namespace (unless you assign the result to a name). -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 21, 5:37 pm, Cristian [EMAIL PROTECTED] wrote: A friend of mine is an engineer and he's been needing to do more and more programming as he goes on with is career. I convinced him to learn Python instead of Perl and he's really started to like it. He usually comes to me when he can't accomplish a task with his current knowledge and I introduce him to a new feature in Python. FYIW, he thought List Comprehensions were freakin' awesome. He's started writing his own personal scripts for tasks like web scraping. So, from personal experience, Python truly is a great first language to learn. Although his learning experience has gone mostly smoothly, he's hit a lot of speed bumps with functions. Specifically, he's having trouble thinking of functions as first order data (don't worry, I haven't confused him with such terminology yet). He had a little trouble understanding that you can pass functions as arguments to other functions (e.g., passing a key to the list.sort method). He also had a little trouble grasping functions within other functions. Last but not least, he had trouble grasping methods in class declarations, especially the required self as the first argument (I'm sure he wasn't the first). Now, my friend's a smart guy so I know it isn't any lack of brain cells on his part. I still remember many students in my CS classes having trouble grasping the very same concept. And, after we finally get a hold of first order functions, we appreciate its incorporation into languages. It would be a shame if my friend just learns the motions and never incorporates first order functions into his programs. I began to wonder if there was anything Python could do to help newcomers grasp the power of first order functions or, as Pythonistas put it, everything is an object. To me, the biggest setback for new programmers is the different syntax Python has for creating functions. Instead of the common (and easy to grasp) syntax of foo = bar Python has the def foo(): syntax. So, when a new programmer is first introduced to functions they are immediately confronted with the notion that functions are different. After all, they have their own special syntax. This seems to only further the separation newbies make between data and functions or stuff and actions. Now, the vast majority of us learned this dichotomy when we first began to program, so we are ingrained to assume and even expect a different syntax for function declaration, but in a program like Python there doesn't seem to be any other reason to have it. Furthermore, I think it actually inhibits the learning of the uninitiated. We can, of course, keep the current syntax as sugar. To someone who's learning to program wouldn't a syntax like the further give them all they need and also reinforces the idea that functions are data just like everything else? my_function = function(foo, bar): pass an_instance_method = function(self, foo): pass a_method_declaration = method(self, foo): pass The last one is mostly my pet peeve of having Python magically create methods out of (what is essentially) a function declaration. When I first learned it, it felt wrong but you had to press through it because there was really no other way of declaring methods. What do you think? Have you hit this roadblock when helping others learn Python? Does the current syntax make you feel that functions are still treated as second class (get it?) citizens? There are already anonymous functions in Python. lambda x, y, z: x + y + z is the same as: def _(x, y, z): return x + y + z As for the method stuff, check out staticmethod(). If you assign staticmethod(function here) to an object, it will be treated as a normal function and not as a method. I have my own personal opinions about how methods should be in Python, but, whatever. It's weird to deal with stuff like this: x.y = re.match # Assign a function to an attribute of a class, but it doesn't work because you can't assign anything but methods! x.y = staticmethod(re.match) # Ugly -- http://mail.python.org/mailman/listinfo/python-list
Would Anonymous Functions Help in Learning Programming/Python?
A friend of mine is an engineer and he's been needing to do more and more programming as he goes on with is career. I convinced him to learn Python instead of Perl and he's really started to like it. He usually comes to me when he can't accomplish a task with his current knowledge and I introduce him to a new feature in Python. FYIW, he thought List Comprehensions were freakin' awesome. He's started writing his own personal scripts for tasks like web scraping. So, from personal experience, Python truly is a great first language to learn. Although his learning experience has gone mostly smoothly, he's hit a lot of speed bumps with functions. Specifically, he's having trouble thinking of functions as first order data (don't worry, I haven't confused him with such terminology yet). He had a little trouble understanding that you can pass functions as arguments to other functions (e.g., passing a key to the list.sort method). He also had a little trouble grasping functions within other functions. Last but not least, he had trouble grasping methods in class declarations, especially the required self as the first argument (I'm sure he wasn't the first). Now, my friend's a smart guy so I know it isn't any lack of brain cells on his part. I still remember many students in my CS classes having trouble grasping the very same concept. And, after we finally get a hold of first order functions, we appreciate its incorporation into languages. It would be a shame if my friend just learns the motions and never incorporates first order functions into his programs. I began to wonder if there was anything Python could do to help newcomers grasp the power of first order functions or, as Pythonistas put it, everything is an object. To me, the biggest setback for new programmers is the different syntax Python has for creating functions. Instead of the common (and easy to grasp) syntax of foo = bar Python has the def foo(): syntax. So, when a new programmer is first introduced to functions they are immediately confronted with the notion that functions are different. After all, they have their own special syntax. This seems to only further the separation newbies make between data and functions or stuff and actions. Now, the vast majority of us learned this dichotomy when we first began to program, so we are ingrained to assume and even expect a different syntax for function declaration, but in a program like Python there doesn't seem to be any other reason to have it. Furthermore, I think it actually inhibits the learning of the uninitiated. We can, of course, keep the current syntax as sugar. To someone who's learning to program wouldn't a syntax like the further give them all they need and also reinforces the idea that functions are data just like everything else? my_function = function(foo, bar): pass an_instance_method = function(self, foo): pass a_method_declaration = method(self, foo): pass The last one is mostly my pet peeve of having Python magically create methods out of (what is essentially) a function declaration. When I first learned it, it felt wrong but you had to press through it because there was really no other way of declaring methods. What do you think? Have you hit this roadblock when helping others learn Python? Does the current syntax make you feel that functions are still treated as second class (get it?) citizens? -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 21, 2:48 pm, [EMAIL PROTECTED] wrote: There are already anonymous functions in Python. lambda x, y, z: x + y + z is the same as: def _(x, y, z): return x + y + z As for the method stuff, check out staticmethod(). If you assign staticmethod(function here) to an object, it will be treated as a normal function and not as a method. I have my own personal opinions about how methods should be in Python, but, whatever. It's weird to deal with stuff like this: x.y = re.match # Assign a function to an attribute of a class, but it doesn't work because you can't assign anything but methods! x.y = staticmethod(re.match) # Ugly True, there is lambda, but that is very limited. It might be useful for key arguments, but not much else. It doesn't solve the teaching problem of See, functions are just like any other data type. You can assign it to a variable. It would be a footnote if it's mentioned at all. My hope is to subtly reinforce the notion that functions are data and can be passed around. The current function declaration doesn't help with this. Creating a function and assigning it to a name is exactly what Python does, why not have it come out in the syntax? It's not necessary, yes, but I think it would be helpful for teaching purposes. Again, it's not necessary as much as it's more intuitive and obvious what's going on. This helps a beginner sort out the process from the syntax without taking it on faith. They can see the class declaration and see I'm defining just another attribute to this class only this time it happens to be method. There is nothing functionally lacking in Python. I'm just curious if there's anything Python can do syntax-wise to help a person better grasp programming ideas and Python's inner workings. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 21, 6:07 pm, Cristian [EMAIL PROTECTED] wrote: On Sep 21, 2:48 pm, [EMAIL PROTECTED] wrote: There are already anonymous functions in Python. lambda x, y, z: x + y + z is the same as: def _(x, y, z): return x + y + z As for the method stuff, check out staticmethod(). If you assign staticmethod(function here) to an object, it will be treated as a normal function and not as a method. I have my own personal opinions about how methods should be in Python, but, whatever. It's weird to deal with stuff like this: x.y = re.match # Assign a function to an attribute of a class, but it doesn't work because you can't assign anything but methods! x.y = staticmethod(re.match) # Ugly True, there is lambda, but that is very limited. It might be useful for key arguments, but not much else. It doesn't solve the teaching problem of See, functions are just like any other data type. You can assign it to a variable. It would be a footnote if it's mentioned at all. My hope is to subtly reinforce the notion that functions are data and can be passed around. The current function declaration doesn't help with this. Creating a function and assigning it to a name is exactly what Python does, why not have it come out in the syntax? It's not necessary, yes, but I think it would be helpful for teaching purposes. Again, it's not necessary as much as it's more intuitive and obvious what's going on. This helps a beginner sort out the process from the syntax without taking it on faith. They can see the class declaration and see I'm defining just another attribute to this class only this time it happens to be method. There is nothing functionally lacking in Python. I'm just curious if there's anything Python can do syntax-wise to help a person better grasp programming ideas and Python's inner workings. Guido apparently doesn't like lambda; I'm not really sure why, it's extremely useful. There were rumors of it leaving in Python 3000, but thankfully there was the decision to keep them. (I have a feeling if they weren't kept in, a project fork would have happened or such.) Anyway, one of the biggest problems implementation wise is indentation in an expression - there is no expression currently that uses significant whitespace. Python draws a pretty clear line between expression and statement. I do agree with you however, it seems as if there is an arbitrary line between function definitions and normal variable assignment that shouldn't be there for the sake of consistency. A question: if you WERE to implement function definitions as normal expressions, how would you go about embedding it within an expression? x = map(def a: line of code line of code line of code , [1, 2, 3]) It looks hideous in my opinion and lining up the , with the def is ugly. Not to mention currently, inside groupings, whitespace is ignored. How would you handle a whitespace signif. expression inside a grouping which by definition ignores whitespace? -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 21, 3:22 pm, [EMAIL PROTECTED] wrote: On Sep 21, 6:07 pm, Cristian [EMAIL PROTECTED] wrote: On Sep 21, 2:48 pm, [EMAIL PROTECTED] wrote: There are already anonymous functions in Python. lambda x, y, z: x + y + z is the same as: def _(x, y, z): return x + y + z As for the method stuff, check out staticmethod(). If you assign staticmethod(function here) to an object, it will be treated as a normal function and not as a method. I have my own personal opinions about how methods should be in Python, but, whatever. It's weird to deal with stuff like this: x.y = re.match # Assign a function to an attribute of a class, but it doesn't work because you can't assign anything but methods! x.y = staticmethod(re.match) # Ugly True, there is lambda, but that is very limited. It might be useful for key arguments, but not much else. It doesn't solve the teaching problem of See, functions are just like any other data type. You can assign it to a variable. It would be a footnote if it's mentioned at all. My hope is to subtly reinforce the notion that functions are data and can be passed around. The current function declaration doesn't help with this. Creating a function and assigning it to a name is exactly what Python does, why not have it come out in the syntax? It's not necessary, yes, but I think it would be helpful for teaching purposes. Again, it's not necessary as much as it's more intuitive and obvious what's going on. This helps a beginner sort out the process from the syntax without taking it on faith. They can see the class declaration and see I'm defining just another attribute to this class only this time it happens to be method. There is nothing functionally lacking in Python. I'm just curious if there's anything Python can do syntax-wise to help a person better grasp programming ideas and Python's inner workings. Guido apparently doesn't like lambda; I'm not really sure why, it's extremely useful. There were rumors of it leaving in Python 3000, but thankfully there was the decision to keep them. (I have a feeling if they weren't kept in, a project fork would have happened or such.) Anyway, one of the biggest problems implementation wise is indentation in an expression - there is no expression currently that uses significant whitespace. Python draws a pretty clear line between expression and statement. I do agree with you however, it seems as if there is an arbitrary line between function definitions and normal variable assignment that shouldn't be there for the sake of consistency. A question: if you WERE to implement function definitions as normal expressions, how would you go about embedding it within an expression? x = map(def a: line of code line of code line of code , [1, 2, 3]) It looks hideous in my opinion and lining up the , with the def is ugly. Not to mention currently, inside groupings, whitespace is ignored. How would you handle a whitespace signif. expression inside a grouping which by definition ignores whitespace? Yeah, I agree, that does look pretty ugly. Correct me if I'm wrong, but I thought the way Python determines a block is by the whitespace of the first line. So, as long as the spacing (or !tabbing!) is consistent from line to line the parser will know it's part of the same block. From that I don't think the parser would have much trouble extracting the function definition from the above example. I would change the word def. That's never been informative enough for me. I would follow Javascript and call it function. Also, I think parentheses should be required. If there's no implementation problem, I don't see why Python shouldn't allow the above example, but I would certainly discourage it. Just like Python doesn't prevent you from writing an insanely long and convoluted function, Python shouldn't enforce any arbitrary length in anonymous functions. I think the above example should be discouraged as a style violation, not syntax. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian wrote: My hope is to subtly reinforce the notion that functions are data and can be passed around. The current function declaration doesn't help with this. Creating a function and assigning it to a name is exactly what Python does, why not have it come out in the syntax? It's not necessary, yes, but I think it would be helpful for teaching purposes. I think key may be to discuss names and name binding with your friend. How a name is not the object it self, like a variable is in other languages. For example show him how an object can have more than one name. And discus how names can be bound to nearly anything, including classes and functions. Again, it's not necessary as much as it's more intuitive and obvious what's going on. This helps a beginner sort out the process from the syntax without taking it on faith. They can see the class declaration and see I'm defining just another attribute to this class only this time it happens to be method. There is nothing functionally lacking in Python. I'm just curious if there's anything Python can do syntax-wise to help a person better grasp programming ideas and Python's inner workings. You could also discus factory functions with him. Once he gets that a function can return another function, then it won't be so much of a leap for a function to take a function as an argument. Of course he'll figure out all this sooner or later anyway. You can't be an engineer without a fair amount of brain cells committed to processing abstract concepts. Cheers, Ron -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. How a name is not the object it self, like a variable is in other languages. For example show him how an object can have more than one name. And discus how names can be bound to nearly anything, including classes and functions. I could discuss name binding but it would be great if Python said this itself. After all, you can even bind a module with the foo = bar syntax by using __import__ function. If function definitions followed the same pattern, I think a beginner would subconsciously (maybe even consciously) realize that function names are just like everything else. Actually, this would be helpful for many people. If you come from a language like Java you're used to thinking of attributes and methods as living in different namespaces. I think a new syntax will encourage seasoned programmers think in a more Pythonic way. Python has done a very good job in easing people into programming. My friend doesn't come to me very often because the syntax is clear and simple and the builtin datatypes allow you to do so much. My goal is that I would never have to explain to him about name binding; that he'd pick it up by learning the language on his own. He's learned lists, dictionaries and even some OOP without me. I don't think name binding would be a stretch. You could also discus factory functions with him. Once he gets that a function can return another function, then it won't be so much of a leap for a function to take a function as an argument. I think this isn't the most intuitive way of approaching first order functions. It's true that if a function can return another function then a function must be first order (i.e., it's just like any other variable), but that seems almost backwards to me. I think it would make more sense to have beginners _know_ that functions are like all other variables and can therefore be passed by other functions or returned by other functions. That I think would be better accomplished if they define functions the same way you would define other variables that you know can be passed and returned. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. How a name is not the object it self, like a variable is in other languages. For example show him how an object can have more than one name. And discus how names can be bound to nearly anything, including classes and functions. I could discuss name binding but it would be great if Python said this itself. After all, you can even bind a module with the foo = bar syntax by using __import__ function. If function definitions followed the same pattern, I think a beginner would subconsciously (maybe even consciously) realize that function names are just like everything else. Actually, this would be helpful for many people. If you come from a language like Java you're used to thinking of attributes and methods as living in different namespaces. I think a new syntax will encourage seasoned programmers think in a more Pythonic way. However, you still have to solve the problem of using a single-line construct (x = y) with a multi-line definition. That is the essential difference that def is designed to solve. The __import__ trick works because import is also a single line construct. The only proposal given in this thread is using consistent indentation within the parentheses, but parentheses are already explicitly designed to let you ignore the whitespace rules. To suddenly create a situation in which you have significant whitespace on the right side of an assignment statement, and *within parentheses* will break too much code, and make the solution unnecessarily ugly. Multi-line lambdas have been rejected because of this very problem, so unless you have a clean solution, I think your proposal falls into the category of would be nice, but not in Python. Cheers, Cliff -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
In article [EMAIL PROTECTED],
Cristian [EMAIL PROTECTED] wrote:
...
To someone who's learning to program wouldn't a syntax like the
further give them all they need and also reinforces the idea that
functions are data just like everything else?
my_function = function(foo, bar): pass
an_instance_method = function(self, foo): pass
a_method_declaration = method(self, foo): pass
I think one followup has already alluded to the division
between Python `statements' and `expressions'. The `def'
statement may create and bind a value, but since it's a
statement and not an expression, it doesn't have any value.
Python is not a functional programming language. It probably
could be reinvented to eliminate statements, but ... there
are already plenty of languages to choose from.
If we're going there, though, I think it's obvious that
once you have defined
an_instance_method = function(self, foo): ...
it should be invoked
an_instance_method(an_instance, foo)
which would be much less messy in nested expressions where
the current standard OOP notation flips from right to left
too much ...
string.join(x.split('-'), '').lower()
-- lower(string.join('', split(x, '-')))
It might make for some interesting problems, but that's what
it's about, changing things so it stays fun for everyone.
At the same time, partial function parameter binding should
be implemented, so you could say
dotted = string.join('.')
...
v = dotted(['comp', 'lang', 'python'])
As you probably well know, that isn't my idea, it's a common
functional programming language idiom.
Donn Cave, [EMAIL PROTECTED]
--
http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Just tell him that functions are like all other variables and can therefore be passed by other functions or returned by other functions. If your friend understands variables and functions and he can't make the leap (and assuming you're right, of course) then your friend doesn't understand variables and functions. Happy Friday. Sean On 9/21/07, Cristian [EMAIL PROTECTED] wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. How a name is not the object it self, like a variable is in other languages. For example show him how an object can have more than one name. And discus how names can be bound to nearly anything, including classes and functions. I could discuss name binding but it would be great if Python said this itself. After all, you can even bind a module with the foo = bar syntax by using __import__ function. If function definitions followed the same pattern, I think a beginner would subconsciously (maybe even consciously) realize that function names are just like everything else. Actually, this would be helpful for many people. If you come from a language like Java you're used to thinking of attributes and methods as living in different namespaces. I think a new syntax will encourage seasoned programmers think in a more Pythonic way. Python has done a very good job in easing people into programming. My friend doesn't come to me very often because the syntax is clear and simple and the builtin datatypes allow you to do so much. My goal is that I would never have to explain to him about name binding; that he'd pick it up by learning the language on his own. He's learned lists, dictionaries and even some OOP without me. I don't think name binding would be a stretch. You could also discus factory functions with him. Once he gets that a function can return another function, then it won't be so much of a leap for a function to take a function as an argument. I think this isn't the most intuitive way of approaching first order functions. It's true that if a function can return another function then a function must be first order (i.e., it's just like any other variable), but that seems almost backwards to me. I think it would make more sense to have beginners _know_ that functions are like all other variables and can therefore be passed by other functions or returned by other functions. That I think would be better accomplished if they define functions the same way you would define other variables that you know can be passed and returned. -- http://mail.python.org/mailman/listinfo/python-list -- Sean Tierney -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On 9/21/07, Sean Tierney [EMAIL PROTECTED] wrote: Just tell him that functions are like all other variables and can therefore be passed by other functions or returned by other functions. If your friend understands variables and functions and he can't make the leap (and assuming you're right, of course) then your friend doesn't [might not] understand variables and functions [and he might need patience b/c this stuff is hard and not everyone is as smart as everyone else]. Happy Friday. Sean [moderately overweight, self-admitted (very) slow learner.] On 9/21/07, Cristian [EMAIL PROTECTED] wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. How a name is not the object it self, like a variable is in other languages. For example show him how an object can have more than one name. And discus how names can be bound to nearly anything, including classes and functions. I could discuss name binding but it would be great if Python said this itself. After all, you can even bind a module with the foo = bar syntax by using __import__ function. If function definitions followed the same pattern, I think a beginner would subconsciously (maybe even consciously) realize that function names are just like everything else. Actually, this would be helpful for many people. If you come from a language like Java you're used to thinking of attributes and methods as living in different namespaces. I think a new syntax will encourage seasoned programmers think in a more Pythonic way. Python has done a very good job in easing people into programming. My friend doesn't come to me very often because the syntax is clear and simple and the builtin datatypes allow you to do so much. My goal is that I would never have to explain to him about name binding; that he'd pick it up by learning the language on his own. He's learned lists, dictionaries and even some OOP without me. I don't think name binding would be a stretch. You could also discus factory functions with him. Once he gets that a function can return another function, then it won't be so much of a leap for a function to take a function as an argument. I think this isn't the most intuitive way of approaching first order functions. It's true that if a function can return another function then a function must be first order (i.e., it's just like any other variable), but that seems almost backwards to me. I think it would make more sense to have beginners _know_ that functions are like all other variables and can therefore be passed by other functions or returned by other functions. That I think would be better accomplished if they define functions the same way you would define other variables that you know can be passed and returned. -- http://mail.python.org/mailman/listinfo/python-list -- Sean Tierney -- Sean Tierney -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 21, 4:27 pm, J. Cliff Dyer [EMAIL PROTECTED] wrote: Cristian wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. How a name is not the object it self, like a variable is in other languages. For example show him how an object can have more than one name. And discus how names can be bound to nearly anything, including classes and functions. I could discuss name binding but it would be great if Python said this itself. After all, you can even bind a module with the foo = bar syntax by using __import__ function. If function definitions followed the same pattern, I think a beginner would subconsciously (maybe even consciously) realize that function names are just like everything else. Actually, this would be helpful for many people. If you come from a language like Java you're used to thinking of attributes and methods as living in different namespaces. I think a new syntax will encourage seasoned programmers think in a more Pythonic way. However, you still have to solve the problem of using a single-line construct (x = y) with a multi-line definition. That is the essential difference that def is designed to solve. The __import__ trick works because import is also a single line construct. The only proposal given in this thread is using consistent indentation within the parentheses, but parentheses are already explicitly designed to let you ignore the whitespace rules. To suddenly create a situation in which you have significant whitespace on the right side of an assignment statement, and *within parentheses* will break too much code, and make the solution unnecessarily ugly. Multi-line lambdas have been rejected because of this very problem, so unless you have a clean solution, I think your proposal falls into the category of would be nice, but not in Python. Cheers, Cliff http://www.artima.com/weblogs/viewpost.jsp?thread=147358 You, Guido, and I all agree that anonymous functions in expressions are ugly. There's no argument there. I wouldn't expect any self respecting programmer to do such a thing even if it was available to them (in Python that is). I suppose my question is, taking into account the potential of ugly code that could be created, and the fact that it's technically feasible, would it still be worth adding anonymous functions to explicitly show the first order nature of functions and show that functions are in the same namespace as all other variables? I suppose a solution could be to allow the my_function = function(foo, bar): ... syntax but throw a syntax error if the function isn't being bound to a variable, but that would cause other problems. From that syntax you would assume that it's possible to create an anonymous function wherever a variable is expected. That's not very intuitive either. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Sep 21, 4:47 pm, Sean Tierney [EMAIL PROTECTED] wrote: Just tell him that functions are like all other variables and can therefore be passed by other functions or returned by other functions. I could Just tell him that functions are like all other variables and can therefore be passed by other functions or returned by other functions. but wouldn't it be great if Python did this for me? It seems to me that the ability for Python to explicitly state that functions-are- like-other-variables is there so why not expose it? If your friend understands variables and functions and he can't make the leap (and assuming you're right, of course) then your friend doesn't understand variables and functions. To say that you understand variables and functions is language specific. You can't translate your knowledge of variables and functions from Python to Java and vice-versa. They are treated completely different. Perhaps you can translate your Python understanding of functions and variables to Javascript but not to C. -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Fri, 21 Sep 2007 21:37:18 +, Cristian wrote: Although his learning experience has gone mostly smoothly, he's hit a lot of speed bumps with functions. Specifically, he's having trouble thinking of functions as first order data (don't worry, I haven't confused him with such terminology yet). He had a little trouble understanding that you can pass functions as arguments to other functions (e.g., passing a key to the list.sort method). He also had a little trouble grasping functions within other functions. Last but not least, he had trouble grasping methods in class declarations, especially the required self as the first argument (I'm sure he wasn't the first). First of all, let me say that I think functions as first class data is helpful, but not crucial, to programming in Python, and there are many people who simply don't need the lesson. Especially someone like an engineer (in the classical sense), who isn't building versatile software packages, won't need to resort to functional programming much. For straightforward tasks, like sorting lists with a custom ordering, functional progamming merely a convenience, and can be done without. So I'm -1 on syntactic changes to the language to support a pedagogical use that's not crucially important. Now, as for the more general question--How do you teach functional concepts?--because some people do need to know it. I suspect it's one of those things where there are two possibilities and not much in between. Either 1. The person gets it right away. or 2. The person doesn't get it right away. In the latter case, trying to teach it conceptually is probably hopeless. Best thing to do is teach functional usage for certain use cases. For instance, teach someone to define a function returning a key, and have them use key=myfunc in list.sort--and not worry about why it works. If they keep at it, eventually one of two things will happen. Either, 2a. The person will have an A ha! I get it now! moment, and will finally understand the concept. or 2b. The person will never get it. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. How a name is not the object it self, like a variable is in other languages. For example show him how an object can have more than one name. And discus how names can be bound to nearly anything, including classes and functions. I could discuss name binding but it would be great if Python said this itself. After all, you can even bind a module with the foo = bar syntax by using __import__ function. If function definitions followed the same pattern, I think a beginner would subconsciously (maybe even consciously) realize that function names are just like everything else. Actually, this would be helpful for many people. If you come from a language like Java you're used to thinking of attributes and methods as living in different namespaces. I think a new syntax will encourage seasoned programmers think in a more Pythonic way. I could see methods having their own keywords. Then functions defined in classes would be static methods without any extra work. But to do that would break a lot of already existing code as well as confuse a lot of current users. Python has done a very good job in easing people into programming. My friend doesn't come to me very often because the syntax is clear and simple and the builtin datatypes allow you to do so much. My goal is that I would never have to explain to him about name binding; that he'd pick it up by learning the language on his own. He's learned lists, dictionaries and even some OOP without me. I don't think name binding would be a stretch. Chances are he'll run into a gotcha where an object has two names and sort it out that way. Which is why I suggested starting there. It will save him some grief if he hasn't run into it yet. You could also discus factory functions with him. Once he gets that a function can return another function, then it won't be so much of a leap for a function to take a function as an argument. I think this isn't the most intuitive way of approaching first order functions. The Python tutorial does this by defining a function, then assigning it to another name and calling it from the new name. http://www.python.org/doc/current/tut/tut.html It's true that if a function can return another function then a function must be first order (i.e., it's just like any other variable), but that seems almost backwards to me. I think it would make more sense to have beginners _know_ that functions are like all other variables and can therefore be passed by other functions or returned by other functions. That I think would be better accomplished if they define functions the same way you would define other variables that you know can be passed and returned. I think it gets awkward fairly quick if you try and work out how to do this. There have been requests in the past to have functions assigned to names like other things. The nice thing about the current syntax is it more closely resembles what you would type at call time, so it is more self documenting. def sum(x, y): return x + Y total = sum(1, 2) I think changing that would be trading one type of clarity for another. Ron -- http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
On Fri, 21 Sep 2007 22:07:55 +, Cristian wrote:
True, there is lambda, but that is very limited. It might be useful for
key arguments, but not much else.
No, lambda is useful for anything that any other function is useful for,
provided that you can write it as a single expression and not need to use
statements. In other words, a lambda function can do anything anything
any other function can, just less conveniently.
(To pick one example at random, you can use print with lambda:
http://northernplanets.blogspot.com/2006/07/python-using-print-with-lambda.html
and while it is easy it isn't exactly convenient.)
And that's basically why function definitions have the syntax they do,
because trying to hammer a multi-line function definition into a single
expression is painful.
It doesn't solve the teaching problem
of See, functions are just like any other data type. You can assign it
to a variable.
Is their interactive interpreter broken?
def parrot(colour='red'):
... return I'm a parrot with %s plumage. % colour
...
bird = parrot # note the lack of brackets
type(bird)
type 'function'
bird('green')
I'm a parrot with green plumage.
Or using lambda:
parrot = lambda colour: I'm a parrot with %s plumage. % colour
parrot(purple)
I'm a parrot with purple plumage.
It would be a footnote if it's mentioned at all. My hope
is to subtly reinforce the notion that functions are data and can be
passed around. The current function declaration doesn't help with this.
Some things just need to be learnt. I'm in favour of making languages
easy for newbies to learn, but making function and method definitions
harder to use just so newbies will be given a subtle reminder of
something that 80% of them will never notice or use anyway is a bad
trade-off.
Creating a function and assigning it to a name is exactly what Python
does, why not have it come out in the syntax? It's not necessary, yes,
but I think it would be helpful for teaching purposes.
If people don't get it when you EXPLICITLY show them that functions are
first-class objects, how do you expect them to notice it on their own
based on the IMPLICIT similarities in syntax?
--
Steven.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Would Anonymous Functions Help in Learning Programming/Python?
Cristian wrote: On Sep 21, 3:44 pm, Ron Adam [EMAIL PROTECTED] wrote: I think key may be to discuss names and name binding with your friend. Here's an idea: import math def sin_integral(start, finish, dx): total = 0.0 y0 = math.sin(start) for n in range(1, 1 + int((finish - start) / float(dx))): y1 = math.sin(start + n * dx) total += (y0 + y1) y0 = y1 return total / 2. * dx def cos_integral(start, finish, dx): total = 0.0 y0 = math.sin(start) for n in range(1, 1 + int((finish - start) / float(dx))): y1 = math.cos(start + n * dx) total += (y0 + y1) y0 = y1 return total / 2. * dx generalize and separate the integration technique from the function it integrates. -- http://mail.python.org/mailman/listinfo/python-list
