Hello I ran the following code in python:
>>> ls = [(lambda op: op + i) for i in [1,2,3]] >>> ls [<function <lambda> at 0xb7de4cdc>, <function <lambda> at 0xb7de4d14>, <function <lambda> at 0xb7de4d4c>] >>> for l in ls: ... print l(5) ... 8 8 8 >>> I am quite surprised of the result. I'm generating three lamdas. What I want to do is that the first lamda adds 1 to the operand and returns it, the second lamda return 2 plus the operand and so on. However all the three lamdas, despite being not the same object in memory, are all adding 3, so they've got to have a reference to and not to 1,2,3 respectively. Why are the lamdas having a reference to the same integer? What am I getting wrong here? :P On Sat, 2007-03-03 at 17:24 +0100, [EMAIL PROTECTED] wrote: > Send Tutor mailing list submissions to > tutor@python.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://mail.python.org/mailman/listinfo/tutor > or, via email, send a message with subject or body 'help' to > [EMAIL PROTECTED] > > You can reach the person managing the list at > [EMAIL PROTECTED] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Tutor digest..." > > > Today's Topics: > > 1. Re: geeks like us and the rest of THEM (Andrei) > 2. Re: dictionaries and memory handling (Andrei) > 3. Re: Yet another list comprehension question (Kent Johnson) > 4. trouble understanding the python environment in OSX > (Clay Wiedemann) > 5. Re: trouble understanding the python environment in OSX > (Alan Gauld) > 6. Re: trouble understanding the python environment in OSX > (Kent Johnson) > 7. Re: Yet another list comprehension question (Andrei) > 8. Re: Yet another list comprehension question (Kent Johnson) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Sat, 03 Mar 2007 13:40:05 +0100 > From: Andrei <[EMAIL PROTECTED]> > Subject: Re: [Tutor] geeks like us and the rest of THEM > To: tutor@python.org > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > <snip> > > That's part of it. a good installer is another, and I am loo]king at a > > couple. A solid and drool-proof server is the remaining leg of the > > tripod. So far, none of the servers I have seen are satisfactory on all > > scores- simplicity to install, reliability, economy of cost, (free or > > unlimited license to me for a modest fee) and ease to configure if the > > use\r so wishes. the closest I have yet seen SMALL HTTP SERVER. And it > > is very good. > > http://smallsrv.com/ > > You could have a look at Aprelium's Abyss server (X1, which is freely > distributable in unmodified form IIRC, but closed source). It has a good > looking webbased configuration console and is cross-platform if you ever > need that. However, you'll probably end up digging in its config > programmatically to set up paths and such for the user - shouldn't be > too hard using some webscraping if the files are not readily modifiable. > Its setup is about 350 kB. > > In terms of installers, NSIS (with the package to make it look modern, > instead of that awful default look - forgot its name) or InnoSetup are > the usual suspects. NSIS has a smaller overhead, but an uglier language. > > -- > Yours, > > Andrei > > ===== > Mail address in header catches spam. Real contact info: > ''.join([''.join(s) for s in zip( > "[EMAIL PROTECTED] pmfe!Pes ontuei ulcpss edtels,s hr' one oC.", > "rjc5wndon.Sa-re laed o s npbi ot.Ira h it oteesn edt C")]) > > > > ------------------------------ > > Message: 2 > Date: Sat, 03 Mar 2007 14:18:24 +0100 > From: Andrei <[EMAIL PROTECTED]> > Subject: Re: [Tutor] dictionaries and memory handling > To: tutor@python.org > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=windows-1252; format=flowed > > > But most of my dictionaries are nested, and since both keys and values > > in the dbm 'dictionaries' have to be strings, I can't immediately see > > how I could get it to work. > > > > A bit more detail: I deal with conditional probabilities, with up to 4 > > parameters. These parameters are numbers or words and determine the > > value (which is always a number). E.g. I have a dictionary > > {p1:{p2:{p3:{p4:value}}}}, where the p's are different parameters. I > > sometimes need to sum over one or more of the parameters ? for now I > > have managed to structure the dictionaries so that I only need to sum > > over the innermost parameter, although this has been a bit cumbersome. > > Depends a bit on how many keys each of the dictionaries is going to have > and in what order they're filled. You can pickle/cPickle an arbitrary > amount of data as one value, so the whole {p2:{p3:{p4:value}}} story > could be a value of the p1 key in the bsddb. However, you may not like > this if you need to retrieve p1 and add new stuff to it all the time, > because the pickling and unpickling cycles may not be beneficial to the > performance. > > If you find this is a problem, you could opt to e.g. keep the first > layer of the dictionary in memory, but map each value to a separate > bsddb, so that you'd need to do less pickling/unpickling. > > Alternatively you could choose to store them as a sort of path in the > bsddb, like this (obviously wasteful in terms of space): > 'p1/p2/p3/p4': '20' > 'p1/p2/p3/p5': '45' > > Combinations of the approaches above are also possible and I have no > idea which would be best. > > >> - Will the dictionaries take up less memory if I use numbers rather > >> than words as keys (i.e. will {3:45, 6:77, 9:33} consume less memory > >> than {"eloquent":45, "helpless":77, "samaritan":33} )? And if so: > >> Slightly less, or substantially less memory? > > Here's a simple test: > > >>> x = [str(i) for i in range(100000, 1000000)] > vs. > >>> x = [i for i in range(100000, 1000000)] > > The interpreter takes about 50 MB for the str() version and about 20 for > the non-str() version - eyeballed in the Task manager. So it does make a > significant difference, though not an order-of-magnitude difference. > That may be enough for now, but if this script stays in use, you're > bound at some point to need even more. > > >> - What are common methods to monitor the memory usage of a script? > >> Can I add a snippet to the code that prints out how many MBs of > >> memory a certain dictionary takes up at that particular time? > > Not as such. In your case, I think the task manager would be enough. You > only have this one demanding data structure I assume, so in a rough > approximation you can pretend that whatever the task manager reports > (have a look at VM and peak memory usage columns, not just memory usage) > is caused by the contents of the dictionary. > > -- > Yours, > > Andrei > > ===== > Mail address in header catches spam. Real contact info: > ''.join([''.join(s) for s in zip( > "[EMAIL PROTECTED] pmfe!Pes ontuei ulcpss edtels,s hr' one oC.", > "rjc5wndon.Sa-re laed o s npbi ot.Ira h it oteesn edt C")]) > > > > ------------------------------ > > Message: 3 > Date: Sat, 03 Mar 2007 08:47:55 -0500 > From: Kent Johnson <[EMAIL PROTECTED]> > Subject: Re: [Tutor] Yet another list comprehension question > To: Alan Gauld <[EMAIL PROTECTED]> > Cc: tutor@python.org > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Alan Gauld wrote: > > "Smith, Jeff" <[EMAIL PROTECTED]> wrote > > > >> In other words, applying somefun to the results of the iterator > >> return > >> duplicates but I want the constructed list to contain none. > > > >> l = [somefun(i) for i some-iterator if somefun(i) not in l] > >> > >> doesn't work (not that I expected it to). > > > > Why not use a Set? > > > > s = Set([somefun(i) for i in some-iterator]) > > > > Might be slow for big lists though... > > This is a popular question. It comes up frequently on comp.lang.python > and there are many recipes in the online cookbook. Here is a FAQ: > http://www.effbot.org/pyfaq/how-do-you-remove-duplicates-from-a-list.htm > > I think using a set is the fastest solution if the list items are > hashable and you don't care about order. > > If the list items are hashable and you do care about order then there is > this mild hack: > s = set() > [ i for i in lst if i not in s and not s.add(i) ] > > but with the requirement of calling somefunc(i) my guess is that an > explicit loop will be faster. > > The cookbook is down right now but there is a link in the above FAQ. > > Kent > > > ------------------------------ > > Message: 4 > Date: Sat, 3 Mar 2007 08:50:09 -0500 > From: "Clay Wiedemann" <[EMAIL PROTECTED]> > Subject: [Tutor] trouble understanding the python environment in OSX > To: tutor@python.org > Message-ID: > <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Hi, > > I am not only new to Python, but new to programming in an environment > like this, where knowing a little of how the underpinning work is > essential.* > > I am running the latest OSX (10.4.8) and know a little about moving > about in the terminal. But the world of paths, etc. has me a little > confused. And now it is getting in my way. I was wondering if I could > get a little help with some things. > > - Can anyone point me to a well-regarded and pithy tutorial regarding > the UNIX underpinnings of OSX, especially anything that would help > with Python. (e.g., I can navigate to Python.framework and versions > but see 2.5 and Current, which confuses me since 2.5 is the current > version.) I would love to know what the structure of the Python > installation means. > > - I am having trouble installing the BeautifulSoup package. The > installer stumbles on a unicode issue (that the Soup developer says is > a problem with my Python installation) -- so what is the best way to > manually install this? And does the 2.5 / Current divide matter? > > > > Thanks in advance for any help with these basic issues. > > Good morning from Brooklyn, > Clay > > > * Any experience with coding webpages is not helping here > > > > - - - - - - - > > Clay S. Wiedemann > > aim: khlav > wii: 3905 4571 6175 2469 > twitter: seastokes > > > ------------------------------ > > Message: 5 > Date: Sat, 3 Mar 2007 14:22:11 -0000 > From: "Alan Gauld" <[EMAIL PROTECTED]> > Subject: Re: [Tutor] trouble understanding the python environment in > OSX > To: tutor@python.org > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; format=flowed; charset="iso-8859-1"; > reply-type=original > > > "Clay Wiedemann" <[EMAIL PROTECTED]> wrote > > > I am not only new to Python, but new to programming in an > > environment > > like this, where knowing a little of how the underpinning work is > > essential.* > > Actually I very rarely need to do anything with the environment. > Most of my iBook Python programming is done in the > src/python folder of my home directory. I just import > stuff and it works... > > > I am running the latest OSX (10.4.8) and know a little about moving > > about in the terminal. But the world of paths, etc. has me a little > > confused. > > If you have specific situations where paths are tripping you > up we can probably offer help. In general you should only need > 1) The path to Python set up in your login shell script PATH > 2) The path to Pythons modules in PYTHONPATH > ie. in your file: ~/.bash_profile. > (I assume you use bash since think thats the new default > in 10.4 - I am still on 10.2 which uses tcsh as shell) > > > - Can anyone point me to a well-regarded and pithy tutorial > > regarding > > the UNIX underpinnings of OSX, especially anything that would help > > with Python. > > Apple have lots of guidance, this is a good jump off page: > > http://developer.apple.com/referencelibrary/GettingStarted/GS_MacOSXServer/index.html > > Or more usefully there is Pogue's Missing Manual book. > This is probably best for traditional Mac users stepping into Unix > for the first time. > For more depth I found MacOS X Unleashed good, but longgggg > And finally MacOSX Hacks is good but not really a tutorial. > > HTH, > > > -- > Alan Gauld > Author of the Learn to Program web site > http://www.freenetpages.co.uk/hp/alan.gauld > > > > > ------------------------------ > > Message: 6 > Date: Sat, 03 Mar 2007 09:20:43 -0500 > From: Kent Johnson <[EMAIL PROTECTED]> > Subject: Re: [Tutor] trouble understanding the python environment in > OSX > To: Clay Wiedemann <[EMAIL PROTECTED]> > Cc: tutor@python.org > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Clay Wiedemann wrote: > > > I am running the latest OSX (10.4.8) and know a little about moving > > about in the terminal. But the world of paths, etc. has me a little > > confused. And now it is getting in my way. I was wondering if I could > > get a little help with some things. > > > > - Can anyone point me to a well-regarded and pithy tutorial regarding > > the UNIX underpinnings of OSX, especially anything that would help > > with Python. (e.g., I can navigate to Python.framework and versions > > but see 2.5 and Current, which confuses me since 2.5 is the current > > version.) I would love to know what the structure of the Python > > installation means. > > Current is an alias for 2.5, which is the current install. > > > > - I am having trouble installing the BeautifulSoup package. The > > installer stumbles on a unicode issue (that the Soup developer says is > > a problem with my Python installation) -- so what is the best way to > > manually install this? And does the 2.5 / Current divide matter? > > What is the error you get in the installer? > > The installer is not really needed in this case. You should be able to > just download the single file and put it in > .../Current/lib/python2.5/site-packages > > Kent > > > > > > > > Thanks in advance for any help with these basic issues. > > > > Good morning from Brooklyn, > > Clay > > > > > > * Any experience with coding webpages is not helping here > > > > > > > > - - - - - - - > > > > Clay S. Wiedemann > > > > aim: khlav > > wii: 3905 4571 6175 2469 > > twitter: seastokes > > _______________________________________________ > > Tutor maillist - Tutor@python.org > > http://mail.python.org/mailman/listinfo/tutor > > > > > > ------------------------------ > > Message: 7 > Date: Sat, 03 Mar 2007 16:43:00 +0100 > From: Andrei <[EMAIL PROTECTED]> > Subject: Re: [Tutor] Yet another list comprehension question > To: tutor@python.org > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > >> Alternatively, you could put the results as keys in a dictionary, > >> then request > >> mydict.keys() to get a list of unique outcomes. > > > > I thought of that too, but couldn't think how to do it in a list > > comprehension. It seemed like it should be possible but I > > couldn't think of how - and didn't have a python interpreter > > handy... > > I wouldn't do it in a list comprehension - I took a bit of liberty with > the topic and looked more at the actual problem :). Of course the loop > can be turned into a list comprehension, but it serves no purpose > whatsoever: > > >>> d = {} > >>> [d.__setitem__(s, '') for s in myiterator] > > By the way, the fromkeys method of the dict type can turn this into a > oneliner: > > >>> mylist = [1,2,3,1,2,4] # may also be some iterator > >>> print dict.fromkeys(mylist).keys() > ... [1,2,3,4] > > The set solution is the Most Obvious Way to do it, but the dict one > doesn't require an understanding of list comprehensions. > > -- > Yours, > > Andrei > > ===== > Mail address in header catches spam. Real contact info: > ''.join([''.join(s) for s in zip( > "[EMAIL PROTECTED] pmfe!Pes ontuei ulcpss edtels,s hr' one oC.", > "rjc5wndon.Sa-re laed o s npbi ot.Ira h it oteesn edt C")]) > > > > ------------------------------ > > Message: 8 > Date: Sat, 03 Mar 2007 11:24:35 -0500 > From: Kent Johnson <[EMAIL PROTECTED]> > Subject: Re: [Tutor] Yet another list comprehension question > To: Andrei <[EMAIL PROTECTED]> > Cc: tutor@python.org > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Andrei wrote: > >>> Alternatively, you could put the results as keys in a dictionary, > >>> then request > >>> mydict.keys() to get a list of unique outcomes. > >> I thought of that too, but couldn't think how to do it in a list > >> comprehension. It seemed like it should be possible but I > >> couldn't think of how - and didn't have a python interpreter > >> handy... > > > > I wouldn't do it in a list comprehension - I took a bit of liberty with > > the topic and looked more at the actual problem :). Of course the loop > > can be turned into a list comprehension, but it serves no purpose > > whatsoever: > > > > >>> d = {} > > >>> [d.__setitem__(s, '') for s in myiterator] > > > > By the way, the fromkeys method of the dict type can turn this into a > > oneliner: > > > > >>> mylist = [1,2,3,1,2,4] # may also be some iterator > > >>> print dict.fromkeys(mylist).keys() > > ... [1,2,3,4] > > > > The set solution is the Most Obvious Way to do it, but the dict one > > doesn't require an understanding of list comprehensions. > > The list comp in Alan's solution is just needed to introduce somefunc(). > You have to do the same in yours to match the original problem. The set > version of your solution doesn't need a list comp either, it is just > list(set(mylist)) > > There is really no reason in modern Python to use dicts as sets. > > Kent > > > ------------------------------ > > _______________________________________________ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > > End of Tutor Digest, Vol 37, Issue 10 > ************************************* _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
