Fraud
My phone my accounts my home network have all been affected because of someone using coding from Python and Linux and GitHub and json. I don't even know what this stuff is but how do I get rid of it all. It's ruined my life. Sent from my iPhone -- https://mail.python.org/mailman/listinfo/python-list
Re: anomaly
On Sun, 10 May 2015 14:12:44 -0500, boB Stepp wrote: I have to admit being surprised by this, too. I am just now studying on how to write my own classes in Python, and have come to realize that doing this is *possible*, but the *surprise* to me is why the language design allowed this to actually be done. Read Cory Doctorow lately on the War Against General Purpose Computing, where a bunch of people who don't really understand are trying to make it impossible for any computer to do something that is The Wrong Thing. Or gently approach the relevant computing theory through Doug Hofstadter's _Goedel, Escher, Bach_, or some essays in _Metamagical Themas_. Generally speaking, making a computer totally incapable of doing Wrong Things leaves it incapable of doing anything at all. Mel. -- https://mail.python.org/mailman/listinfo/python-list
Re: anomaly
On Tue, 12 May 2015 02:35:23 +1000, Steven D'Aprano wrote: On Mon, 11 May 2015 11:37 pm, Mel Wilson wrote: On Sun, 10 May 2015 14:12:44 -0500, boB Stepp wrote: I have to admit being surprised by this, too. I am just now studying on how to write my own classes in Python, and have come to realize that doing this is *possible*, but the *surprise* to me is why the language design allowed this to actually be done. Read Cory Doctorow lately on the War Against General Purpose Computing, where a bunch of people who don't really understand are trying to make it impossible for any computer to do something that is The Wrong Thing. I think you are conflating two different ideas of the Wrong Thing. I don't think so. A formal solution to a problem, i.e. a solution coded as a computer program, is limited to the things that can be done using formal techniques. Whether it's people trying to enact their social standards in code, or whether it's people trying to nail the door shut against everything they don't expect, or think is illogical, the limits will still be there. Mel. -- https://mail.python.org/mailman/listinfo/python-list
Re: Instead of deciding between Python or Lisp for a programming intro course...What about an intro course that uses *BOTH*? Good idea?
On Sun, 10 May 2015 13:43:03 -0700, Chris Seberino wrote: Instead of learning only Scheme or only Python for a one semester intro course, what about learning BOTH? Maybe that could somehow get the benefits of both? I'm thinking that for the VERY beginning, Scheme is the fastest language to get beginners up and running writing code due to the extremely minimal simple syntax. I'm thinking half way into the semester, instead of moving into intermediate Scheme, perhaps that is a good time to switch to Python? Would a little strong intro to 2 nice languages in one semester be same/good/worse/better than just 1? The first course I took, we learned Algol-60, then when we couldn't get computer time for compiles, we were asked to pick up FORTRAN-IV on the side. So we published our solutions to the class problems in Algol and re-wrote them to be run in FORTRAN. It was a fine first-hand look at what the general purpose in General Purpose Computer really meant. There was no confusing the machine and the language after that. Scheme/ Python would be even more radical, I think. If you can put them across effectively, I say go for it. Mel. cs -- https://mail.python.org/mailman/listinfo/python-list
Re: How to properly apply OOP in the bouncing ball code
On Fri, 08 May 2015 08:40:34 -0700, Tommy C wrote: I'm trying to apply OOP in this bouncing ball code in order to have multiple balls bouncing around the screen. The objective of this code is to create a method called settings, which controls all the settings for the screen and the bouncing behaviour of multiple balls, under the class Ball. However, I keep on getting errors related to attributes (e.g., speed). I'm new to OOP in Python so your help will be much appreciated. Thanks in advance. I did something similar, with little characters running around the screen under joystick control. What I think: 1. Each instance of the Ball class should control the behaviour of one ball. 2. The screen settings and global environment generally should be global, not stuffed inside the behaviour of a Ball. 3. Keeping the list of Ball instances should be something the main section of your program does, not stuffed inside the behaviour of a Ball. Each of my little GamePlayer objects is subclassed from pygame.sprite.Sprite . I forget what I got by doing this (it's old code) but looking up the docs for that class might give you some insights. Each GamePlayer object has an update method which accepts info from the joystick and updates the player's movements, and a draw method which the main loop calls on displaying every frame, to show the player's new position and attitude. You might be able to do something along these lines. Mel. -- https://mail.python.org/mailman/listinfo/python-list
Re: functions, optional parameters
On Sat, 09 May 2015 03:49:36 +1000, Chris Angelico wrote:
Yes, but can you *distinguish* them in terms of default argument versus
code object creation? How do you know that the function's code object
was created when compile() happened, rather than being created when the
function was defined? Is there anything that lets you in any way show
different behaviour based on that timing difference?
This might show that default objects are fixed at run time:
Python 2.7.3 (default, Mar 14 2014, 11:57:14)
[GCC 4.7.2] on linux2
Type help, copyright, credits or license for more information.
a = []
def b (arr=a):
... arr.append ('c')
...
print repr(a)
[]
b()
print repr(a)
['c']
b()
print repr(a)
['c', 'c']
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Re: New to Python - block grouping (spaces)
On Sun, 19 Apr 2015 09:03:23 -0700, Rustom Mody wrote: Now if Thomson and Ritchie (yeah thems the guys) could do it in 1970, why cant we revamp this 45-year old archaic program=textfile system today? Dunno. Why not? There's half of you right there. -- https://mail.python.org/mailman/listinfo/python-list
Re: New to Python - block grouping (spaces)
On Mon, 20 Apr 2015 03:53:08 +1000, Steven D'Aprano wrote: On Mon, 20 Apr 2015 02:03 am, Rustom Mody wrote: Well evidently some people did but fortunately their managers did not interfere. You are assuming they had managers. University life isn't exactly the same as corporate culture. IIRC Thompson, Ritchie, et al. were working at Bell Labs. Legend has it that management would not buy them a Multics, so they were forced to write their own using the hardware they had. Mel. -- https://mail.python.org/mailman/listinfo/python-list
Re: Best search algorithm to find condition within a range
On Wed, 08 Apr 2015 07:56:05 -0700, jonas.thornvall wrote: There is no need for inventing a new set of characters representing 32-bit numbers. You will not be able to learn them by heart anyway, unless they build on a interpretation system binaries, decimals. See Jorge Luis Borges, _Funes the Memorious_. Gotta keep up with the literature. -- https://mail.python.org/mailman/listinfo/python-list
Re: Best search algorithm to find condition within a range
On Tue, 07 Apr 2015 23:19:49 -0700, jonas.thornvall wrote: And you have just created 429496729 unique symbols ;), in a pencil stroke. No. You did that, when you said base 429496729. Representing the symbols in a computer is no problem, any Python long int can do that. To display the symbols, you can use PIL to make up glyphs out of coloured pixels 864x864. You can keep your glyphs in GIFs. Where you keep them is up to you. Keeping them in Tumbolia and computing them out as required will work well. -- https://mail.python.org/mailman/listinfo/python-list
Re: Programming D. E. Knuth in Python with the Deterministic Finite Automaton construct
Antti J Ylikoski wrote: In his legendary book series The Art of Computer Programming, Professor Donald E. Knuth presents many of his algorithms in the form that they have been divided in several individual phases, with instructions to GOTO to another phase interspersed in the text of the individual phases. I. e. they look like the following, purely invented, example: (Knuth is being clearer than me below.) A1. (Do the work of Phase A1.) If zap then go to Phase A5, otherwise continue. A2. (Do some work.) If zorp go to Phase A4. A3. (Some more work.) A4. (Do something.) If condition ZZZ go to Phase A1. A5. (Something more). If foobar then go to Phase A2, otherwise end. I came across the problem, which would be the clearest way to program such algorithms with a programming language such as Python, which has no GOTO statement. It struck me that the above construction actually is a modified Deterministic Finite Automaton with states A1 -- A5 + [END], transferring to different states, not on read input, but according to conditions in the running program. So one very clear way to program Knuth with Python is the following kind of a construct. Yeah. This is an idea that came up during the '70s after Dijkstra published his GOTO Considered Harmful. Model the execution pointer as a state, and then explicit changes to the execution pointer (prohibited in GOTO-less languages) get replaced by assignments to the state. It preserves the objectionable part of GOTO: that there's no easy way to predict the conditions that any statement might execute under. You can't understand any of the program until you understand all of the program. I think Knuth kept the assembly-language model for his algorithms because it promotes his real goal, which is mathematical analysis of the performance of the algorithms. It helps that his algorithms are very short. As the quickest way to get a Knuth algorithm running in Python, this is a pretty good idea. My own preference is to get the algo really coded in Python, but that usually takes a fair bit of time and effort. Mel. -- http://mail.python.org/mailman/listinfo/python-list
[issue14353] Proper gettext support in locale module
Mel Flynn rfl...@acsalaska.net added the comment: Additional patch for 2.7 branch. -- Added file: http://bugs.python.org/file24918/python27-configure.in.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14353 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14353] Proper gettext support in locale module
New submission from Mel Flynn rfl...@acsalaska.net: Gettext support in Python is configured by two tests: - textdomain in libc or libintl - bind_textdomain_codeset in libc only The latter causes incomplete gettext support in the locale module. Since the implementation uses two different defines, the provided patch provides them and also ensures they exist. The issue is not present in 3.x branches, as only a single test is done for full gettext support in locale. -- components: Build files: python26-configure.in.patch keywords: patch messages: 156203 nosy: melflynn priority: normal severity: normal status: open title: Proper gettext support in locale module type: enhancement versions: Python 2.6, Python 2.7 Added file: http://bugs.python.org/file24917/python26-configure.in.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14353 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
Re: Python is readable
Steven D'Aprano wrote: On Fri, 16 Mar 2012 17:53:24 +, Neil Cerutti wrote: On 2012-03-16, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Ah, perhaps you're talking about *prescriptivist* grammarians, who insist on applying grammatical rules that exist only in their own fevered imagination. Sorry, I was talking about the other sort, the ones who apply the grammatical rules used by people in real life. You know the ones: linguists. My mistake. I am not pedantic. You are wrong. Whether you like it or not, it simply is a fact that in English (I won't speak for other languages) people use colons without the first clause *necessarily* being a complete sentence. They write things like this: Star Wars Episode IV: A New Hope Come to think of it, just about every serious book title works this way. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: A 'Python like' language
Paul Rubin wrote: dreamingforw...@gmail.com writes: hanging out on the Prothon list now and then, at least until we get the core language sorted out? Haha, a little late, but consider this a restart. It wasn't til I saw the word Prothon that I scrolled back and saw you were responding to a thread from 2004. Prothon was pretty cool in some ways but I think it's been inactive for a very long time. I don't see much point to developing a slightly improved but incompatible Python-like language anyway though. Why make superficial changes that break working code and mentally overload programmers? Python is a relatively mature language by now, so it shouldn't be messed with unless the changes produce drastic benefits, not minor ones. A website still exists, but I don't see signs of a new language; looks like a watering hole for some techies. Prothon looked interesting as long as it promised to be about Python that used prototypes instead of classes to organize objects. What happened, though, was that it turned into a crusade to remove every Python wart that a bunch of people could imagine. The band of developers might have had the steam for the new object model, but they didn't have the steam to do everything. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is it necessary to call Tk() when writing a GUI app with Tkinter?
Terry Reedy wrote: The problem was another subtle bug in the current example: self.hi_there[text] = Hello, The spurious comma at the end makes the value of the 'text' attribute a one-elememt tuple and not just a string. I presume tcl-based tk handles that in the manner appropriate for the tcl equivalent. I believe tcl uses spaces rather than commas to separate items, so the braces serve as 'quotes' to indicate that the contents are one item, not three. Removing the comma solves the problem. That looks like it. Tcl is the 'LISP of strings' Composite-object things like indexing work on space-separated strings. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: Language missing maximum constant of numeric types!
Rick Johnson wrote: I get sick and tired of doing this!!! if maxlength == UNLIMITED: allow_passage() elif len(string) maxlength: deny_passage() What Python needs is some constant that can be compared to ANY numeric type and that constant will ALWAYS be larger! Easily fixed: class Greatest (object): def __cmp__ (self, other): if isinstance (other, Greatest): return 0 return 1 def __hash__ (self): return id (Greatest) class Least (object): def __cmp__ (self, other): if isinstance (other, Least): return 0 return -1 def __hash__ (self): return id (Least) Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: atexit.register in case of errors
Andrea Crotti wrote: I have the following very simplified situation from atexit import register def goodbye(): print(saying goodbye) def main(): while True: var = raw_input(read something) if __name__ == '__main__': register(goodbye) main() But in my case the goodbye function is deleting the logging file which was created during the application execution. Now the problem is that it *always* executes, even when the applications quits for some bad errors. Is there a way to have an exit hook, which doesn't execute in case of errors? I've seen the code of atexit and it apparently doesn't know anything about the current status and why the application is actually quitting, is that correct? That's sort of the point: to do things that simply *have* to happen, even if you've lost control of the program. The usual way to do what you're asking is if __name__ == '__main__': main() goodbye() and write main so that it returns after it's done all the things it's supposed to do. If you've sprinkled `sys.exit()` all over your code, then don't do that. If you're forced to deal with a library that hides `sys.exit()` calls in the functions, then you have my sympathy. Library authors should not do that, and there have been threads on c.l.p explaining why they shouldn't. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: name of a sorting algorithm
Jabba Laci wrote: Could someone please tell me what the following sorting algorithm is called? Let an array contain the elements a_1, a_2, ..., a_N. Then: for i in xrange (N-1): for j in xrange (i, N): if a[j] a[i]: a[i], a[j] = a[j], a[i] It's so simple that it's not mentioned anywhere. I guess it's called selection sort but I'm not sure. The minimum selection sort is an improvement of this one. It's what Wikipedia says a selection sort is: put the least element in [0], the least of the remaining elements in [1], etc. Mel. -- http://mail.python.org/mailman/listinfo/python-list
RE: name of a sorting algorithm
Prasad, Ramit wrote: for i in xrange (N-1): for j in xrange (i, N): if a[j] a[i]: a[i], a[j] = a[j], a[i] It's what Wikipedia says a selection sort is: put the least element in [0], the least of the remaining elements in [1], etc. If your only requirement to match to selection sort is the end result, then every sort would be selection sort. If you meant put the least element in [0] in the first pass then that would indeed be selection sort, but that is not what the above code does. The above code is bubble sort. Well, the classic bubble sort swaps adjacent elements until the extreme one gets all the way to the end. This sort continually swaps with the end element during one pass until the end element holds the extreme. Then it shrinks the range and swaps then next less extreme into the new end element. It does extra swaps because it combines the swap operation with recording the temporary extreme while it searches the subrange. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: name of a sorting algorithm
Den wrote: I disagree. In a bubble sort, one pointer points to the top element, while another descents through all the other elements, swapping the elements at the pointers when necessary. 'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean — neither more nor less.' (_Through the Looking Glass, Lewis Caroll). And you, too, have that ability. Contrariwise see Knuth, _The Art of Computer Programming_ Section 5.2.2, Algorithm B. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: M2crypto
zigi wrote: Hello, M2crypto __init__(self, alg, key, iv, op, key_as_bytes=0, d='md5', salt='12345678', i=1, padding=1) I wont write app, using M2crypto and I can not understand what are the arguments: key, iv, op, salt ? What they do ? I assume you're reading in http://www.heikkitoivonen.net/m2crypto/api/ about M2Crypto.EVP.Cipher. Epydoc claims another victim. I'm having a lot of trouble finding documentation. The obvious OpenSSL pages are kind of thin, too. You might see some useful code in the EVP unit tests m2crypto/tests/test_evp.py in the m2crypto installation. Good hunting, Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: difference between random module in python 2.6 and 3.2?
Steven D'Aprano wrote: A more explicit note will help, but the basic problem applies: how do you write deterministic tests given that the random.methods (apart from random.random itself) can be changed without warning? Biting the bullet would mean supplying your own PRNG, under your control. Jon Bentley somewhere, sometime, published a portable PRNG for that exact reason. (I wish I could find that article.) Specifically he wanted portability across various manufacturer's O/Ss. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: python reliability with EINTR handling in general modules
Dennis Lee Bieber wrote:
On Wed, 1 Feb 2012 23:25:36 -0800 (PST), oleg korenevich
void.of.t...@gmail.com wrote:
Thanks for help. In first case all vars is python integers, maybe
math.floor is redundant, but i'm afraid that same error with math
module call will occur in other places of app, where math is needed.
Strange thing here is that math library call is not a system call, and
strange exception ValueError (all values have right values) and why in
braces i have (4, Interruted system call).
math.floor() may still be a system call of some sort if access to
the math processor requires synchronization between processes (that is,
the math processor/registers are maintained as a separate structure
apart from the task status during process switches). {Yes -- that is a
wild hypothesis}
One thing to remember about errno is that C library code will set it to a
non-zero value when an error is encountered, but (I believe) there's no
requirement to clear it in the absence of an error. EINTR might just be
left over from some long-gone I/O call, then reported just in case in
handling an exception that didn't involve the C library at all.
As a C coder there are times when it's wise to clear errno yourself to make
sure your code doesn't get fooled.
Mel.
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Re: Question about name scope
Dave Angel wrote:
I tried your experiment using Python 2.7 and Linux 11.04
def f(a):
from math import sin, cos
return sin(a) + cos(a)
print f(45)
Does what you needed, and neatly. The only name added to the global
namspace is f, of type function.
I was a bit surprised that using from math import * inside the
function worked, but it generates a warning:
olive.py:2: SyntaxWarning: import * only allowed at module level
def f(a):
I guess they want local symbols in functions to be pre-compiled. Similar to
the way you can't usefully update the dict returned by locals(). Strangely,
I notice that
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
def f(x):
... exec x
... exec 'print a'
...
f('a=4')
4
works, but I really cannot explain why.
Mel.
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Re: except clause syntax question
Charles Yeomans wrote: To catch more than one exception type in an except block, one writes except (A, B, C) as e: I'm wondering why it was decided to match tuples, but not lists: except [A, B, C] as e: The latter makes more sense semantically to me -- catch all exception types in a list as opposed to catch this single thing composed of three exception types. On reflection, it seems to hint at a style that Python extensions were made in. (IIRC) the first operand in an `except` statement was originally just an arbitrary marker to identify the exception. Unique string values were customary, although the Python library defined things with standard exception names. Using a string means that general exceptions weren't to be collected in general sequences; `except Serious Error` was never meant to catch `raise r`. If only tuples were used for collections, it would create havoc for fewer of any weirdos who had used strange markers of their own devising. It looks like tuples were chosen as the most lightweight, or maybe least intrusive, sequence type to require to denote a collection of exceptions. You see a similar decision, with the opposite emphasis, with the string modulo operator. The second operand is supposed to be a tuple, but if the template string needs only one value, then the rules are relaxed and any single non-tuple value is used as-is. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: except clause syntax question
Chris Angelico wrote: On Wed, Feb 1, 2012 at 9:03 AM, Duncan Booth duncan.booth@invalid.invalid wrote: Abitrarily nested tuples of exceptions cannot contain loops so the code simply needs to walk through the tuples until it finds a match. Is this absolutely guaranteed? The C API for CPython provides: (Py2) http://docs.python.org/c-api/tuple.html#PyTuple_SetItem (Py3) http://docs.python.org/dev/c-api/tuple.html#PyTuple_SetItem which doesn't have massive warnings on it saying USE THIS ONLY TO INITIALIZE A TUPLE (compare, for instance, _PyTuple_Resize which does carry a similar warning). Is the assumption then that we're all adults, and that mutating a tuple is like passing a null pointer to an API function (aka loaded gun in proximity to foot)? Unfortunately, I can't remember the details now, but I once set out to create a recursive tuple by using the C API, and it turned out then that the C API went to some lengths to prevent anyone being able to do that. I did finally do it in some peculiar way, but it wasn't simple. The c.l.python archives might still have the post where I described it. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: except clause syntax question
Charles Yeomans wrote: To catch more than one exception type in an except block, one writes except (A, B, C) as e: I'm wondering why it was decided to match tuples, but not lists: except [A, B, C] as e: The latter makes more sense semantically to me -- catch all exception types in a list as opposed to catch this single thing composed of three exception types. I've always been perfectly fine with sometimes treating tuples as immutable sequences, so I'm +0 on saying more sense semantically, but given that the exception list can be a variable, I'm not sure what the gain is by keeping it immutable. #--- #!/usr/bin/env python # -*- coding: ASCII -*- '''Demonstrate catching variable exceptions. ''' def excepter (a, exceptions): try: 1.0/a 'Number ' + a except exceptions as e: print '!!! *** EXCEPTER CAUGHT ONE *** !!!' print repr (e) #~ excepter (0, [ZeroDivisionError]) excepter (0, (ZeroDivisionError,)) excepter (1, (ZeroDivisionError,TypeError)) excepter (1, (ZeroDivisionError,)) #--- excepter called with the list catches nothing, of course. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: verify the return value of a function
Jean-Michel Pichavant wrote: isinstance is fine, if you could find the source where it is discouraged... Could be a consequence of some specific context. However, checking types in OOP is in general a failure. Unitary tests are possibly an exception. I think it's discouraged when people try to write big overloaded functions that check the types of the arguments to decide what they should be doing. In diagnostics and tests like the OP's there should be no problem. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: mutually exclusive arguments to a constructor
Adam Funk wrote: (Warning: this question obviously reflects the fact that I am more accustomed to using Java than Python.) Suppose I'm creating a class that represents a bearing or azimuth, created either from a string of traditional bearing notation (N24d30mE) or from a number indicating the angle in degrees as usually measured in trigonometry (65.5, measured counter-clockwise from the x-axis). The class will have methods to return the same bearing in various formats. In Java, I would write two constructors, one taking a single String argument and one taking a single Double argument. But in Python, a class can have only one __init__ method, although it can have a lot of optional arguments with default values. What's the correct way to deal with a situation like the one I've outlined above? Cleanest from the point of view of the class source code would be factory functions at the module level, or special classmethods to deal with the less common cases. You see this a lot in wxPython when they have to deal with overloaded C++ constructors. Most like the Java would be to check within __init__ for a string argument that could be parsed as a bearing, and failing that fall back to treating the argument as a numeric angle. Neither fish nor fowl would be to accept named arguments for the different kinds of values. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Early and late binding [was Re: what does 'a=b=c=[]' do]
Steven D'Aprano wrote: On Fri, 23 Dec 2011 13:13:38 +, Neil Cerutti wrote: On 2011-12-23, Neil Cerutti ne...@norwich.edu wrote: ...you know, assuming it wouldn't break existing code. ;) It will. Python's default argument strategy has been in use for 20 years. Some code will rely on it. I know mine does. In a tool that's meant for other people to use to accomplish work of their own, breaking workflow is a cardinal sin. In a research language that's meant always to be up-to-date with the concept of the week, not so much. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Pythonification of the asterisk-based collection packing/unpacking syntax
Chris Angelico wrote: On Fri, Dec 23, 2011 at 1:13 AM, Hans Mulder han...@xs4all.nl wrote: How about: class name=MyClass superclasses=A, B, C ... /class More more readable! And it's a standard! Unfortunately it's not Pythonic, because indentation is insignificant. Easy-peasy: def name=method arguments=self, x, y indent/indentlet target=t Mel. We need to adopt a more appropriate form. Eliminate all the /spam tags and use indentation to mark the ends of elements. ChrisA PS. Brilliant, sir, brilliant! I take off my cap to you. -- http://mail.python.org/mailman/listinfo/python-list
Re: Making the case for typed lists/iterators in python
Chris Angelico wrote: It's no more strange than the way some people omit the u from colour. :) Bonum Petronio Arbiteri, bonum mihi. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: correct usage of a generator?
Tim wrote:
Hi, I need to generate a list of file names that increment, like
this:
fname1
fname2
fname3 and so on.
I don't know how many I'll need until runtime so I figure a
generator is
called for.
def fname_gen(stem):
i = 0
while True:
i = i+1
yield '%s%d' % (stem,i)
blarg = fname_gen('blarg')
boo = fname_gen('boo')
n = 3
for w in range(0,n):
in_name = blarg.next()
out_name = boo.next()
This works, but is it the 'normal' way to accomplish the task when
you
don't know 'n' until run-time? thanks,
It's kind of overkill in the toy demo example, but if the main loop is
a little more abstract, e.g.
for task in task_supplier():
in_name = blarg.next()
out_name = boo.next()
handle_task (task, in_name, out_name)
then it's obviously a good thing.
One quibble (that Peter Otten also suggested): if your business rules
expect that files blarg25 and boo25 (for example) work together, then
you'd be better off generating them together as a pair in a single
generator call. As it is, there's a chance of the blarg and boo
generators getting out of step and supplying mismatched names.
Mel.
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Re: Close as Many Files/External resourcs as possible in the face of exceptions
GZ wrote: Here is my situation. A parent object owns a list of files (or other objects with a close() method). The close() method can sometimes fail and raise an exception. When the parent object's close() method is called, it needs to close down as many files it owns as possible, even if the close() function of some files fail. I also want to re-raise at least one of the original exceptions so that the outer program can handle it. [ ... ] It will re-raise the first exception and preserve the context and close as many other files as possible while ignoring any further exceptions. But this looks really awkward. And in the case that two files fail to close, I am not sure the best strategy is to ignore the second failure. I imagine you could save any caught exception instances in a list and study them later. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Use and usefulness of the as syntax
candide wrote: First, could you confirm the following syntax import foo as f equivalent to import foo f = foo Now, I was wondering about the usefulness in everyday programming of the as syntax within an import statement. [ ... ] It gives you an out in a case like Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. os = 5 # number of 'o's import os as opsys os 5 opsys module 'os' from '/usr/lib/python2.6/os.pyc' (This is an instance of what arnaud mentioned.) Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to isolate a constant?
Dennis Lee Bieber wrote:
Where's the line form to split those who'd prefer the first vs the
second result in this sample G:
unExpected = What about a string
firstToLast = unExpected[:]
repr(firstToLast)
'What about a string'
explicitList = list(unExpected)
repr(explicitList)
['W', 'h', 'a', 't', ' ', 'a', 'b', 'o', 'u', 't', ' ', 'a', ' ', 's',
't', 'r', 'i', 'n', 'g']
Well, as things stand, there's a way to get whichever result you need. The
`list` constructor builds a single list from a single iterable. The list
literal enclosed by `[`, `]` makes a list containing a bunch of items.
Strings being iterable introduces a wrinkle, but `list('abcde')` doesn't
create `['abcde']` just as `list(1)` doesn't create `[1]`.
Mel.
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RE: Problem with a wx notebook
Prasad, Ramit wrote: I've created a wx NoteBook in wich I set multiples panels in wich I set one or more sizers. But nothing displays in the notebook, everything is outside. I've been searching an answer for 2 days . Can you help me plz ? Here is my code(with only one panel, to sum up the code) : class StreamingActivationDialog(wx.Dialog): def __init__(self, *args, **kwds): # begin wxGlade: StreamingActivationDialog.__init__ kwds[style] = wx.DEFAULT_DIALOG_STYLE wx.Dialog.__init__(self, *args, **kwds) self.bitmap_1_copy = wx.StaticBitmap(self, -1, wx.Bitmap(img\ \logo.png, wx.BITMAP_TYPE_ANY)) self.labelDnD = wx.StaticText(self, -1, Si vous avez déjà un fichier d'activation, faite le glisser dans cette fenetre) self.keyBitmap = wx.StaticBitmap(self, -1, wx.Bitmap(img\ \key.bmp, wx.BITMAP_TYPE_ANY)) self.conclude = wx.StaticText(self, -1, _(test), style=wx.ALIGN_CENTRE) ### Panel ### self.intro3_label = wx.StaticText(self, -1, Envoyez un mail à \nactivat...@monmail.com\ncontenant le code :,style=wx.ALIGN_CENTRE) self.activationCode_label= wx.StaticText(self, -1, 123456789, style=wx.TE_READONLY) self.copy2_Button = wx.Button(self, -1, Copier dans le presse- papier) self.copy2_Button.Bind(wx.EVT_BUTTON, PanelMail.onCopy) ## self.note = wx.Notebook(self, wx.ID_ANY, style=wx.BK_LEFT, size=wx.Size(100, 341)) self.page3 = wx.Panel(self.note) imagelist = wx.ImageList(94, 94) bitmap1 = wx.Bitmap(img\\a.bmp, wx.BITMAP_TYPE_BMP ) imagelist.Add(bitmap1) self.note.AssignImageList(imagelist) self.__set_properties() self.__do_layout() # end wxGlade def __set_properties(self): # begin wxGlade: StreamingActivationDialog.__set_properties self.SetTitle(_(Activation de FlashProcess)) self.SetBackgroundColour(wx.Colour(255, 255, 255)) #self.linkProblem.SetForegroundColour(wx.Colour(0, 0, 0)) # end wxGlade def __do_layout(self): # begin wxGlade: StreamingActivationDialog.__do_layout self.grid_sizer_1 = wx.FlexGridSizer(6, 1, 0, 0) self.grid_sizer_2 = wx.FlexGridSizer(1, 2, 0, 30) self.grid_sizer_1.Add(self.bitmap_1_copy, 0, wx.TOP|wx.BOTTOM| wx.EXPAND, 10) ### Page 3 ### sizer = wx.BoxSizer(wx.VERTICAL) sizer.Add(self.intro3_label, 0, wx.BOTTOM|wx.ALIGN_CENTER, 5) sizer.Add(self.activationCode_label, 0, wx.BOTTOM| wx.ALIGN_CENTER, 20) sizer.Add(self.copy2_Button, 0, wx.ALIGN_CENTER, 20) self.page3.SetSizer(sizer) sizer.Fit(self.page3) ## self.note.AddPage(self.page3, , False, 0) [ ... ] It looks a though all the controls that are meant for page3 have been created with the top-level dialog as their parent. AFAIK this cannot be. self.page3 is (correctly) a child window of self.note, but the controls to be shown inside have to be children of self.page3 . Putting things into the sizers is not enough. In my own code, I usually define a separate class descended from wx.Panel to create a page3 instance with its own sizers, then create one of those with a a wx.Notebook instance as a parent, and add it to the notebook: def _new_capture_page (self): new_trace = TraceWindow (self.tracebook) self.tracebook.AddPage (new_trace, 'Capture %d' % (self.capture_serial,), select=True) return new_trace Hope this helps, Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Usefulness of the not in operator
Steven D'Aprano wrote: candide wrote: So what is the usefulness of the not in operator ? Recall what Zen of Python tells There should be one-- and preferably only one --obvious way to do it. And not in is the obvious way to do it. If the key is not in the ignition, you won't be able to start the car. If not the key is in the ignition, you won't be able to start the car. Who like that second one speaks? :) If the key is not in the ignition, you will be able to start the car, not. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Wrote a new library - Comments and suggestions please!
Steven D'Aprano wrote: I googled on SAS PROC FREQ and found this: http://support.sas.com/documentation/cdl/en/procstat/63104/HTML/default/procstat_freq_sect006.htm All the words are in English, but I have no idea what the function does, how you would call it, and what it returns. Would it have been so hard to show a couple of examples? Hmm. Yeah. Very much so. That's the kind of documentation I call syntax happy. It tells you how to create a well-formed PROC STAT without ever saying what would happen if you did, or why you might want that, whatever it was, to happen. I see that kind of documentation way too often. By comparison, even this https://www.ubersoft.net/comic/hd/2011/09/losing- sight-big-picture might seem good. At least they try. Does things to the stuff. By default, the most recent stuff is done things to. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Generating equally-spaced floats with least rounding error
Steven D'Aprano wrote: I'm trying to generate a sequence of equally-spaced numbers between a lower and upper limit. Given arbitrary limits, what is the best way to generate a list of equally spaced floats with the least rounding error for each point? For example, suppose I want to divide the range 0 to 2.1 into 7 equal intervals, then the end-points of each interval are: (0.0)---(0.3)---(0.6)---(0.9)---(1.2)---(1.5)---(1.8)---(2.1) and I'd like to return the values in the brackets. Using Decimal or Fraction is not an option, I must use floats. If the exact value isn't representable as a float, I'm okay with returning the nearest possible float. The width of each interval is: width = (2.1 - 0.0)/7 The relevant points can be calculated in either of two methods: #1 add multiples of the width to the starting value, 0. #2 subtract multiples of width from the ending value, 2.1. (Repeated addition or subtraction should be avoided, as it increases the amount of rounding error.) Mathematically the two are equivalent, but due to rounding, they may not be. Here's a run using Python 3.2: [0.0 + i*width for i in range(8)] [0.0, 0.3, 0.6, 0.8999, 1.2, 1.5, 1.7998, 2.1] The 4th and 7th values have rounding errors, the rest are exact. [2.1 - (7-i)*width for i in range(8)] [0.0, 0.30027, 0.6001, 0.9001, 1.2002, 1.5, 1.8, 2.1] The 2nd, 3rd, 4th and 5th values have rounding errors. Note that the 7th value is exact here, but not above. Is there a way to pick between methods #1 and #2 (or some combination of the two) without human intervention so as to minimise the rounding error? Or is there some other way to generate equally-spaced floats? My efforts at googling have not been helpful. When I've done this with ints (usually in small embedded systems) I've always preferred low_limit + (total_width * i) / intervals since it does the rounding on the biggest numbers where proportional error will be least, and it's guaranteed to hit the low_limit and high_limit exactly (as exactly as they can be represented, anyway.) Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Context manager with class methods
Gavin Panella wrote: Hi, On Python 2.6 and 3.1 the following code works fine: class Foo(object): @classmethod def __enter__(cls): print(__enter__) @classmethod def __exit__(cls, exc_type, exc_value, traceback): print(__exit__) with Foo: pass However, in 2.7 and 3.2 I get: Traceback (most recent call last): File stdin, line 1, in module AttributeError: __exit__ Is this a regression or a deliberate change? Off the top of my head I can't think that this pattern is particularly useful, but it seems like something that ought to work. This seems to work: class MetaWith (type): @classmethod def __enter__(cls): print(__enter__) @classmethod def __exit__(cls, exc_type, exc_value, traceback): print(__exit__) class With (object): __metaclass__ = MetaWith with With: pass Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Context manager with class methods
Mel wrote: This seems to work: class MetaWith (type): @classmethod def __enter__(cls): print(__enter__) @classmethod def __exit__(cls, exc_type, exc_value, traceback): print(__exit__) class With (object): __metaclass__ = MetaWith with With: pass It seems to work equally well without the `@classmethod`s Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Doctest failing
Tigerstyle wrote:
Hi guys.
I'm strugglin with some homework stuff and am hoping you can help me
out here.
This is the code:
small_words = ('into', 'the', 'a', 'of', 'at', 'in', 'for', 'on')
def book_title(title):
Takes a string and returns a title-case string.
All words EXCEPT for small words are made title case
unless the string starts with a preposition, in which
case the word is correctly capitalized.
book_title('DIVE Into python')
'Dive into Python'
book_title('the great gatsby')
'The Great Gatsby'
book_title('the WORKS OF AleXANDer dumas')
'The Works of Alexander Dumas'
new_title = []
title_split = title.strip().lower().split()
for word in title_split:
if title_split[0] in small_words:
new_title.append(word.title())
elif word in small_words:
new_title.append(word.lower())
else:
new_title.append(word.title())
return(' '.join(new_title))
def _test():
import doctest, refactory
return doctest.testmod(refactory)
if __name__ == __main__:
_test()
All tests are failing even though I am getting the correct output on
the first two tests. And the last test still gives me Of instead of
of
Any help is appreciated.
I don't know about doctest -- I suspect it wants a structured docstring to
specify the tests -- but this
if title_split[0] in small_words:
new_title.append(word.title())
can't be what you want.
Mel.
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Re: Mastering Python... Best Resources?
Chris Angelico wrote: [ ... ] You can get books on algorithms from all sorts of places, and with a very few exceptions, everything you learn with apply to Python and also to every other language you use. I liked _Programming Pearls_ by Jon Bentley. No reference to Python -- that would be the O.P.'s job. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: is there any principle when writing python function
smith jack wrote: i have heard that function invocation in python is expensive, but make lots of functions are a good design habit in many other languages, so is there any principle when writing python function? It's hard to discuss in the abstract. A function should perform a recognizable step in solving the program's problem. If you prepared to write your program by describing each of several operations the program would have to perform, then you might go on to plan a function for each of the described operations. The high-level functions can then be analyzed, and will probably lead to functions of their own. Test-driven development encourages smaller functions that give you a better granularity of testing. Even so, the testable functions should each perform one meaningful step of a more general problem. for example, how many lines should form a function? Maybe as few as one. def increase (x, a): return x+a is kind of stupid, but a more complicated line def expand_template (bitwidth, defs): '''Turn Run-Length-Encoded list into bits.''' return np.array (sum (([bit]*(count*bitwidth) for count, bit in defs), []), np.int8) is the epitome of intelligence. I wrote it myself. Even increase might be useful: def increase (x, a): return x + a * application_dependent_quantity `increase` has become a meaningful operation in the imaginary application we're discussing. For an upper bound, it's harder to say. If you read to the end of a function and can't remember how it started, or what it did in between, it's too big. If you're reading on your favourite screen, and the end and the beginning are more than one page-scroll apart, it might be too big. If it's too big, factoring it into sub-steps and making functions of some of those sub-steps is the fix. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: try... except with unknown error types
xDog Walker wrote: On Friday 2011 August 19 12:09, Yingjie Lin wrote: [ ... ] Does anyone know what error type I should put after the except statement? or even better: is there a way not to specify the error types? Thank you. You probably need to import urllib2 before you can use urllib2.HTTPError. Otherwise, you can try using the base class: except Exception, e: There are maybe better base classes to use. Running the interpreter: Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. import urllib2 help (urllib2.HTTPError) will show you class HTTPError(URLError, urllib.addinfourl) | Raised when HTTP error occurs, but also acts like non-error return | | Method resolution order: | HTTPError | URLError | exceptions.IOError | exceptions.EnvironmentError | exceptions.StandardError | exceptions.Exception | exceptions.BaseException So catching any of urllib2.HTTPError, urllib2.URLError, IOError, EnvironmentError, or StandardError will detect the exception -- with increasing levels of generality. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: pairwise combination of two lists
Yingjie Lin wrote:
I have two lists:
li1 = ['a', 'b']
li2 = ['1', '2']
and I wish to obtain a list like this
li3 = ['a1', 'a2', 'b1', 'b2']
Is there a handy and efficient function to do this, especially when li1
and li2 are long lists.
I found zip() but it only gives [('a', '1'), ('b', '2')], not exactly
what I am looking for.
This seems to do it :
mwilson@tecumseth:~$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
import itertools
li1 = ['a', 'b']
li2 = ['1', '2']
map (lambda (x,y):x+y, list (itertools.product (li1, li2)))
['a1', 'a2', 'b1', 'b2']
Mel.
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Re: pairwise combination of two lists
Mel wrote: Yingjie Lin wrote: I have two lists: li1 = ['a', 'b'] li2 = ['1', '2'] and I wish to obtain a list like this li3 = ['a1', 'a2', 'b1', 'b2'] [ ... ] This seems to do it : mwilson@tecumseth:~$ python Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. import itertools li1 = ['a', 'b'] li2 = ['1', '2'] map (lambda (x,y):x+y, list (itertools.product (li1, li2))) ['a1', 'a2', 'b1', 'b2'] I have doubts about this in Python3, since tuple unpacking in a argument list isn't done there, and I don't think sum works on strings. Some other function can probably be made to work. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Observations on the three pillars of Python execution
Steven D'Aprano wrote: There may be some other obscure built-in type that includes code objects, but I can't imagine what it would be. I feel confident in saying that functions, and functions alone, contain code. Even methods are just wrappers around functions. Even built-in functions like len don't contain code! (Or at least, their code isn't accessible from Python.) Which makes sense, if you think about it: their code is part of the Python virtual machine, not the object. Interesting question. Iterators seem to have code objects: Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. a = [1, 2, 3] b = (x for x in a) dir(b) ['__class__', '__delattr__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__iter__', '__name__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'close', 'gi_code', 'gi_frame', 'gi_running', 'next', 'send', 'throw'] for name in dir(b): ... print name, type (getattr (b, name)) ... __class__ type 'type' __delattr__ type 'method-wrapper' __doc__ type 'NoneType' __format__ type 'builtin_function_or_method' __getattribute__ type 'method-wrapper' __hash__ type 'method-wrapper' __init__ type 'method-wrapper' __iter__ type 'method-wrapper' __name__ type 'str' __new__ type 'builtin_function_or_method' __reduce__ type 'builtin_function_or_method' __reduce_ex__ type 'builtin_function_or_method' __repr__ type 'method-wrapper' __setattr__ type 'method-wrapper' __sizeof__ type 'builtin_function_or_method' __str__ type 'method-wrapper' __subclasshook__ type 'builtin_function_or_method' close type 'builtin_function_or_method' gi_code type 'code' gi_frame type 'frame' gi_running type 'int' next type 'method-wrapper' send type 'builtin_function_or_method' throw type 'builtin_function_or_method' in the form of the gi_code attribute. No idea what it's for, although no reason to believe it shouldn't be there. (Very interesting demo you gave of primitive object creation. I' awed.) Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: I am fed up with Python GUI toolkits...
sturlamolden wrote: On 20 Jul, 11:59, Thomas Jollans t...@jollybox.de wrote: It is perfectly reasonable to be required to manually call some sort of destroy() method to tell the toolkit what you no longer want the user to see Yes, but not to avoid a memory leak. OTOH, if you intend to re-use the Dialog object, it's not a memory leak. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Tabs -vs- Spaces: Tabs should have won.
Andrew Berg wrote: I should also mention that this mostly speculation on my part, and that I would love to hear from someone who develops for these devices. There's a mailing list for Python scripting on Android -- List-Subscribe: http://groups.google.com/group/python-for- android/subscribe?hl=en_US, mailto:python-for- android+subscr...@googlegroups.com . Tends to be pretty detail-oriented. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Tabs -vs- Spaces: Tabs should have won.
Andrew Berg wrote: I should also mention that this mostly speculation on my part, and that I would love to hear from someone who develops for these devices. There's a mailing list for Python scripting on Android -- List-Subscribe: http://groups.google.com/group/python-for- android/subscribe?hl=en_US, mailto:python-for- android+subscr...@googlegroups.com . Tends to be pretty detail-oriented. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: None versus MISSING sentinel -- request for design feedback
Steven D'Aprano wrote: Well yes, but None is an explicit missing value too. The question I have is if I should support None as that value, or something else. Or if anyone can put a good case for it, both, or neither and so something completely different. If it's any help, I think (some of?) the database interface packages already do just that, returning None when they find NULL fields. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: more advanced learning resources (code structure, fundamentals)
John [H2O] wrote: [ ... ] What are the key points to the classes? Is it okay to reference or pass classes to instantiate a class? Yes. The standard library does this in BaseHTTPServer (via its parent SocketServer.) Maybe looks abstruse at the outset, but it's the natural way to assign a fresh message handler to a new input message. Docs are via the Python Global Module Index, source is in some directory like /usr/lib/python2.6/SocketServer.py , .../BaseHTTPServer.py , etc. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit initialization is EXCELLENT
Ian Kelly wrote: On Wed, Jul 6, 2011 at 12:49 AM, Ulrich Eckhardt ulrich.eckha...@dominolaser.com wrote: Mel wrote: In wx, many of the window classes have Create methods, for filling in various attributes in two-step construction. I'm not sure why, because it works so well to just supply all the details when the class is called and an instance is constructed. Maybe there's some C++ strategy that's being supported there. Just guessing, is it legacy, C-with-classes code rather than C++ code perhaps? Haven't looked at wx for a while. Such code typically lacks understanding of exceptions, which are the only way to signal failure from e.g. constructors. No, wx is C++ through and through. For the why of it, see: http://wiki.wxpython.org/TwoStageCreation The More Details section is particularly illuminating. Yes, it is. Many thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: Does hashlib support a file mode?
Phlip wrote: If I call m = md5() twice, I expect two objects. I am now aware that Python bends the definition of call based on where the line occurs. Principle of least surprise. Actually, in def file_to_hash(path, m = hashlib.md5()): hashlib.md5 *is* called once; that is when the def statement is executed. Later on, when file_to_hash gets called, the value of m is either used as is, as the default parameter, or is replaced for the duration of the call by another object supplied by the caller. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit initialization is EXCELLENT
Steven D'Aprano wrote: [ ... ] Python generally follows this design. Apart from files, I can't easily think off the top of my head of any types that require a separate open/start/activate call before they are usable. It's also relevant to tkinter, which will implicitly create a root window for you when needed. Since you can't do anything without a root window, I don't see the benefit in forcing the user to do so. When they need to learn about root windows, they will in their own good time. In wx, many of the window classes have Create methods, for filling in various attributes in two-step construction. I'm not sure why, because it works so well to just supply all the details when the class is called and an instance is constructed. Maybe there's some C++ strategy that's being supported there. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Significant figures calculation
Erik Max Francis wrote: Chris Angelico wrote: On Tue, Jun 28, 2011 at 12:56 PM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Zero sig figure: 0 That's not really zero significant figures; without further qualification, it's one. Is 0.0 one sig fig or two? Two. (Just vaguely curious. Also curious as to whether a zero sig figures value is ever useful.) Yes. They're order of magnitude estimates. 1 x 10^6 has one significant figure. 10^6 has zero. By convention, nobody ever talks about 1 x 9.97^6 . Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Significant figures calculation
Erik Max Francis wrote: Mel wrote: Erik Max Francis wrote: Chris Angelico wrote: On Tue, Jun 28, 2011 at 12:56 PM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Zero sig figure: 0 That's not really zero significant figures; without further qualification, it's one. Is 0.0 one sig fig or two? Two. (Just vaguely curious. Also curious as to whether a zero sig figures value is ever useful.) Yes. They're order of magnitude estimates. 1 x 10^6 has one significant figure. 10^6 has zero. By convention, nobody ever talks about 1 x 9.97^6 . Not sure what the relevance is, since nobody had mentioned any such thing. If it was intended as a gag, I don't catch the reference. I get giddy once in a while.. push things to limits. It doesn't really mean anything. The point was that it's only the 2 in a number like 2e6 that is taken to have error bars. The 6 is always an absolute number. As is the 10 in 2*10**6. The thought also crossed my mind of a kind of continued fraction in reverse -- 2e1.3e.7 . I managed to keep quiet about that one. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: writable iterators?
Steven D'Aprano wrote: On Wed, 22 Jun 2011 15:28:23 -0400, Neal Becker wrote: AFAICT, the python iterator concept only supports readable iterators, not write. Is this true? for example: for e in sequence: do something that reads e e = blah # will do nothing I believe this is not a limitation on the for loop, but a limitation on the python iterator concept. Is this correct? Have you tried it? e = blah certainly does not do nothing, regardless of whether you are in a for loop or not. It binds the name e to the value blah. seq = [1, 2] for e in seq: ... print(e) ... e = 42 ... print(e) ... 1 42 2 42 I *guess* that what you mean by writable iterators is that rebinding e should change seq in place, i.e. you would expect that seq should now equal [42, 42]. Is that what you mean? It's not clear. Fortunately, that's not how it works, and far from being a limitation, it would be *disastrous* if iterables worked that way. I can't imagine how many bugs would occur from people reassigning to the loop variable, forgetting that it had a side-effect of also reassigning to the iterable. Fortunately, Python is not that badly designed. And for an iterator like def things(): yield 1 yield 11 yield 4 yield 9 I don't know what it could even mean. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: How can I speed up a script that iterates over a large range (600 billion)?
John Salerno wrote: I'm working on the Project Euler exercises and I'm stumped on problem 3: What is the largest prime factor of the number 600851475143 ? [ ... ] Here is what I have so far. Initially the get_factors function just iterated over the entire range(2, n + 1), but since a number can't have a factor greater than half of itself, I tried to shorten the range by doing range(2, n //2), but that still leaves 300 billion numbers to go through. def get_factors(number): factors = [number] for n in range(2, number // 2): if number % n == 0: factors.append(n) return factors def get_primes(number_list): primes = number_list[:] for n in number_list: for x in range(2, n): if n % x == 0: primes.remove(n) break return primes print(max(get_primes(get_factors(600851475143 Also, I want to make it clear that I DO NOT WANT THE ANSWER. I really want to solve this myself, but the reason I'm asking about it is to see if there really is some way to change this code so that it can get an answer in less than one minute, as the website says should be possible. A hint about what I need to do would be nice, but not an answer. I just don't see any way to get the factors without iterating over the entire range of values, though. It certainly can be done faster. I ran it against the factor finder that I wrote, and it popped up the answer mwilson@tecumseth:~$ bin/factors.py 600851475143 71 839 1471 ... before I could glance at my watch. factors.py works, as does yours, by testing for small factors first, but it divides them out as it goes, so it tends to do its work on smallish numbers. And since the smallest factors are taken out as soon as possible, they have to be the prime ones. Good hunting, Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Handling import errors
Guillaume Martel-Genest wrote: What is the pythonic way to handle imports error? What is bugging me is that the imports can't be inside a function (because I use them in different places in the script and thus they have to be in the global scope). Actually, you can if you declare them global: Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. def f(): ... global os ... import os ... dir (os) Traceback (most recent call last): File stdin, line 1, in module NameError: name 'os' is not defined f() dir (os) ['EX_CANTCREAT', 'EX_CONFIG', 'EX_DATAERR', 'EX_IOERR', 'EX_NOHOST', 'EX_NOINPUT', 'EX_NOPERM', 'EX_NOUSER', 'EX_OK', 'EX_OSERR', 'EX_OSFILE', 'EX_PROTOCOL', 'EX_SOFTWARE', 'EX_TEMPFAIL', 'EX_UNAVAILABLE', 'EX_USAGE', 'F_OK', 'NGROUPS_MAX', 'O_APPEND', 'O_ASYNC', 'O_CREAT', 'O_DIRECT', 'O_DIRECTORY', 'O_DSYNC', 'O_EXCL', 'O_LARGEFILE', 'O_NDELAY', 'O_NOATIME', 'O_NOCTTY', 'O_NOFOLLOW', 'O_NONBLOCK etc. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: sorry, possibly too much info. was: Re: How can I speed up a script that iterates over a large range (600 billion)?
John Salerno wrote: ::sigh:: Well, I'm stuck again and it has to do with my get_factors function again, I think. Even with the slight optimization, it's taking forever on 20! (factorial, not excitement) :) It's frustrating because I have the Python right, but I'm getting stuck on the math. The problem: What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20? Here's the function (it's in the problem3.py file, hence the import below): import math def get_factors(number): factors = [] for n in range(2, int(math.sqrt(number))): if number % n == 0: factors.append(n) factors.append(number // n) return factors And here's my new script for the new exercise: import math from problem3 import get_factors max_num = 20 n = math.factorial(max_num) factors = get_factors(n) div_all = [] for x in factors: for y in range(2, max_num+1): if x % y != 0: break elif y == max_num: div_all.append(x) print(min(div_all)) It could easily be that I'm simply approaching it all wrong. I just thought that maybe using the factorial of the highest number in the range (in this case, 20) would be an easy way of finding which numbers to test. These are almost trick questions in a way, because of the math behind them. If the question were What is the tallest high-school student in Scranton, PA? then searching a population for the property would be the only way to go. BUT you can also build up the answer knowing the factorization of all the numbers up to 20. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: What's the best way to write this base class?
John Salerno wrote: On Jun 19, 8:52 pm, Chris Kaynor ckay...@zindagigames.com wrote: Having a character class (along with possibly player character, non-player character, etc), make sense; however you probably want to make stuff like health, resources, damage, and any other attributes not be handles by any classes or inheritance in order to allow you to make such data-driven (ie, read from a file). Doing so makes the game much more extendable: using classes, you are likely limited to 5 or 'combinations and a few developers (plus, any designers need to know programming). A basic way to determine between using subclasses over a data driven approach is: is there significantly different back-end behavior or merely attribute differences. Can you give a basic example of how this data-driven approach would work? You don't have to provide any code, just a description would be helpful. Such as, do I create a data file per character, and then have each character instance read/write to that file? Is it good to have so many files open at once, or would they only need to be read, closed, then opened again at the end to write? Battle for Wesnoth is set up this way. I don't know what the code does, but you can go wild creating new classes of character by mixing up new combinations of attribute settings in new configuration files, and injecting them into the standard game config files. AFAIK you are stuck with the attributes the game is programmed for. I've seen no way to create a new dimension for the game -- Conversation, for instance, with currently unknown attributes like vocabulary or tone. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: What's the best way to write this base class?
John Salerno wrote:
[ ... ]
1)
class Character:
def __init__(self, name, base_health=50, base_resource=10):
self.name = name
self.health = base_health
self.resource = base_resource
2)
class Character:
base_health = 50
base_resource = 10
def __init__(self, name):
self.name = name
self.health = base_health
self.resource = base_resource
3)
BASE_HEALTH = 50
BASE_RESOURCE = 10
class Character:
def __init__(self, name):
self.name = name
self.health = BASE_HEALTH
self.resource = BASE_RESOURCE
For completeness, there's also 4)
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
class Character (object):
... health = 50
... def __init__ (self, name):
... self.name = name
... print self.name, self.health
...
Character ('Eunice')
Eunice 50
where the class attribute is used until it's overridden in the instance.
Mel.
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Re: How to form a dict out of a string by doing regex ?
Satyajit Sarangi wrote:
data = GEOMETRYCOLLECTION (POINT (-8.96484375
-4.130859375000), POINT (2.021484375000 -2.63671875),
POINT (-1.40625000 -11.162109375000), POINT
(-11.95312500,-10.89843750), POLYGON
((-21.62109375 1.845703125000,2.46093750
2.197265625000, -18.98437500 -3.69140625,
-22.67578125 -3.33984375, -22.14843750
-2.63671875, -21.62109375
1.845703125000)),LINESTRING (-11.95312500
11.337890625000, 7.73437500 11.513671875000,
12.30468750 2.548828125000, 12.216796875000
1.669921875000, 14.501953125000 3.955078125000))
This is my string .
How do I traverse through it and form 3 dicts of Point , Polygon and
Linestring containing the co-ordinates ?
Except for those space-separated number pairs, it could be a job for some
well-crafted classes (e.g. `class GEOMETRYCOLLECTION ...`, `class POINT
...`) and eval.
My approach would be to use a loop with regexes to recognize the leading
element and pick out its arguments, then use the string split and strip
methods beyond that point. Like (untested):
recognizer = re.compile (r'(?(POINT|POLYGON|LINESTRING)\s*\(+(.*?)\)+,(.*)')
# regex is not good with nested brackets,
# so kill off outer nested brackets..
s1 = 'GEOMETRYCOLLECTION ('
if data.startswith (s1):
data = data (len (s1):-1)
while data:
match = recognizer.match (data)
if not match:
break # nothing usable in data
## now the matched groups will be:
## 1: the keyword
## 2: the arguments inside the smallest bracketed sequence
## 3: the rest of data
## so use str.split and str.match to pull out the individual arguments,
## and lastly
data = match.group (3)
This is all from memory. I might have got some details wrong in recognizer.
Mel.
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Re: Dynamic Zero Padding.
Friedrich Clausen wrote:
I want to print some integers in a zero padded fashion, eg. :
print(Testing %04i % 1)
Testing 0001
but the padding needs to be dynamic eg. sometimes %05i, %02i or some
other padding amount. But I can't insert a variable into the format
specification to achieve the desirable padding.
I would be much obliged if someone can give me some tips on how to
achieve a variably pad a number.
:)
('%%0%dd' % (pads,)) % (n,)
Probably be good to wrap it in a function. It looks kind of obscure as it
is.
Mel.
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Re: Lambda question
jyoun...@kc.rr.com wrote:
I was surfing around looking for a way to split a list into equal
sections. I came upon this algorithm:
f = lambda x, n, acc=[]: f(x[n:], n, acc+[(x[:n])]) if x else acc
f(Hallo Welt, 3)
['Hal', 'lo ', 'Wel', 't']
http://stackoverflow.com/questions/312443/how-do-you-split-a-list-into-
evenly-s
ized-chunks-in-python/312644
It doesn't work with a huge list, but looks like it could be handy in
certain
circumstances. I'm trying to understand this code, but am totally lost.
I know a little bit about lambda, as well as the ternary operator, but how
does this part work:
f('dude'[3:], 3, []+[('dude'[:3])])
['dud', 'e']
Is that some sort of function call, or something else? I'm guessing it
works recursively?
Yeah, recursive.
f('dude', 3)
evaluates to
f('e', 3, []+['dud']) if 'dude' else []
which evaluates to
f('', 3, []+['dud']+['e']) if 'e' else []+['dud']
which evaluates to
[]+['dud']+['e']
because the if...else finally takes the second branch since the x value is
now an empty string.
I've left the list additions undone .. tracing the actual data objects would
show plain lists. One of the disadvantages of lambdas is that you can't
stick trace printouts into them to clarify what's happening. Rewriting the
thing as a plain def function would be instructive.
Mel.
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Re: scope of function parameters
Henry Olders wrote: I just spent a considerable amount of time and effort debugging a program. The made-up code snippet below illustrates the problem I encountered: def main(): a = ['a list','with','three elements'] print a print fnc1(a) print a def fnc1(b): return fnc2(b) def fnc2(c): c[1] = 'having' return c This is the output: ['a list', 'with', 'three elements'] ['a list', 'having', 'three elements'] ['a list', 'having', 'three elements'] I had expected the third print statement to give the same output as the first, but variable a had been changed by changing variable c in fnc2. It seems that in Python, a variable inside a function is global unless it's assigned. This rule has apparently been adopted in order to reduce clutter by not having to have global declarations all over the place. I would have thought that a function parameter would automatically be considered local to the function. It doesn't make sense to me to pass a global to a function as a parameter. It doesn't look like a question of local or global. fnc2 is passed a container object and replaces item 1 in that container. You see the results when fnc2 prints the object it knows as `c`, and you see again when main prints the object it knows as `a`. Python doesn't pass parameters by handing around copies that can be thought of as local or global. Python passes parameters by binding objects to names in the callee's namespace. In your program the list known as `a` in main is identically the same list as the one known as `c` in fnc2, and what happens happens. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: bug in str.startswith() and str.endswith()
Terry Reedy wrote: To me, that says pretty clearly that start and end have to be 'positions', ie, ints or other index types. So I would say that the error message is a bug. I see so reason why one would want to use None rather that 0 for start or None rather than nothing for end. If you're trying to wrap a call to startswith in a function that looks like startswith, there's no easy way to pass in the information that your caller wants the default parameters. The case I ran into was def wrapped_range (start, stop=None, span=None): do_some_things() result = range (start, stop, span) # range doesn't(/didn't) accept this return result Tne answer in that case was to take *args as the parameter to wrapped_range and count arguments to distinguish between the different calls to range. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python's super() considered super!
sturlamolden wrote: I really don't like the Python 2 syntax of super, as it violates the DRY principle: Why do I need to write super(type(self),self) when super() will do? Assuming that 'self' will always be named 'self' in my code, I tend to patch __builtins__.super like this: import sys def super(): self = sys._getframe().f_back.f_locals['self'] return __builtins__.super(type(self),self) This way the nice Python 3.x syntax can be used in Python 2.x. Python causes trouble by letting the users get at the internals, but things like this make it worthwhile. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: bug in str.startswith() and str.endswith()
Ethan Furman wrote:
I've tried this in 2.5 - 3.2:
-- 'this is a test'.startswith('this')
True
-- 'this is a test'.startswith('this', None, None)
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: slice indices must be integers or None or have an __index__
method
The 3.2 docs say this:
str.startswith(prefix[, start[, end]])
Return True if string starts with the prefix, otherwise return False.
prefix can also be a tuple of prefixes to look for. With optional start,
test string beginning at that position. With optional end, stop
comparing string at that position
str.endswith(suffix[, start[, end]])
Return True if the string ends with the specified suffix, otherwise
return False. suffix can also be a tuple of suffixes to look for. With
optional start, test beginning at that position. With optional end, stop
comparing at that position.
Any reason this is not a bug?
It's a wart at the very least. The same thing happened in Python2 with
range and xrange; there seemed no way to explicitly pass default
arguments.
Mel.
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Re: Obtaining a full path name from file
Tim Golden wrote:
On 24/05/2011 16:36, RVince wrote:
s = C:\AciiCsv\Gravity_Test_data\A.csv
f = open(s,r)
How do I obtain the full pathname given the File, f? (which should
equal C:\AciiCsv\Gravity_Test_data). I've tried all sorts of stuff
and am just not finding it. Any help greatly appreciated !
You're going to kick yourself:
f.name
There's trouble there, though:
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
f = open ('xyzzy.txt')
f.name
'xyzzy.txt'
import os
os.getcwd()
'/home/mwilson'
os.chdir('sandbox')
f.name
'xyzzy.txt'
If you open a file and don't get a full path from os.path.abspath right
away, the name in the file instance can get out-of-date.
Mel.
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Re: What other languages use the same data model as Python?
Steven D'Aprano wrote: It's not an awful model for Python: a name binding a = obj is equivalent to sticking a reference (a pointer?) in box a that points to obj. Certainly there are advantages to it. But one problem is, the model is ambiguous with b = a. You've drawn little boxes a and b both pointing to the big box (which I deleted for brevity). But surely, if a = 1234 creates a reference from a to the big box 1234, then b = a should create a reference from b to the box a? :) There's a way around that too. Describe literals as magic names or Platonic names that are bound to objects in ideal space. I actually considered that for a while as a way of explaining to newbs why the characters in a string literal could be different from the characters in the string value. This would probably have troubles of its own; I never took it through the knock-down drag-out disarticulation that would show what the problems were. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: What other languages use the same data model as Python?
John Nagle wrote: On 5/4/2011 5:46 PM, harrismh777 wrote: Or, as stated earlier, Python should not allow 'is' on immutable objects. A reasonable compromise would be that is is treated as == on immutable objects. I foresee trouble testing among float(5), int(5), Decimal(5) ... Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: What other languages use the same data model as Python?
Tim Roberts wrote: That is not an instance of passing an int by reference. That is an instance of passing an int * by value. The fact that the parameter a in BumpMe happens to be an address is completely irrelevent to the definition of the parameter passing mechanism. C has pass-by-value, exclusively. End of story. Trouble with Turing-complete languages. If it can be done, you can convince a Turing-complete language to do it -- somehow. PL/I was the converse. All parameters were passed by reference, so with some_proc (rocks); the code in some_proc would be working with the address of rocks. If you wanted pass-by-value you wrote some_proc ((rocks)); whereupon the compiler would pass in by reference an unnamed temporary variable whose value was the expression `(rocks)`. I suspect the compiler I used avoided FORTRAN's troubles the same way. Your function could corrupt *a* 4, but it wouldn't corrupt the *only* 4. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: What other languages use the same data model as Python?
Steven D'Aprano wrote: Some day, we'll be using quantum computers without memory addresses, [ ... ] it will still be possible to represent data indirectly via *some* mechanism. :) Cool! Pass-by-coincidence! And Python 3 already has dibs on the 'nonlocal' keyword! Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: What other languages use the same data model as Python?
Hans Georg Schaathun wrote: On 01 May 2011 08:45:51 GMT, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: : Python uses a data model of name binding and call by object (also : known as call by sharing). I trust I don't need to define my terms, : but just in case: Without having the time to get my hand around exactly what this means: Simula has three ways of transmitting arguments, namely transmission by name, by value, and by reference. Is transmission by name the same as call by object? Anyway, I have never seen anyone counting more than three ways of doing this ... To illustrate the neither-fish-nor-fowl nature of Python calls: mwilson@tecumseth:~$ python Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. def identify_call (a_list): ... a_list[0] = If you can see this, you don't have call-by-value ... a_list = [If you can see this, you have call-by-reference] ... my_list = [None] identify_call (my_list) my_list [If you can see this, you don't have call-by-value] so it's neither call-by-value nor call-by-reference as (e.g.) C or PL/I programming would have it (don't know about Simula, so I am off topic, actually.) It's not so wrong to think of Python's parameter handling as ordinary assignments from outer namespaces to an inner namespace. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Why do directly imported variables behave differently than those attached to imported module?
Dun Peal wrote: Hi! Here's the demonstrating code: # module foo.py var = 0 def set(): global var var = 1 Script using this module: import foo from foo import * print var, foo.var set() print var, foo.var Script output: 0 0 0 1 Apparently, the `var` we imported from `foo` never got set, but `foo.var` on the imported `foo` - did. Why? They're different because -- they're different. `foo.var` is defined in the namespace of the foo module. Introspectively, you would access it as `foo.__dict__['var']` . Plain `var` is in your script's namespace so you could access it as `globals()['var']` . The values given to the vars are immutable integers, so assignment works by rebinding. The two different bindings in foo.__dict__ and globals() get bound to different integer objects. Note too the possible use of `globals()['foo'].__dict__['var'] . (Hope there are no typos in this post.) Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
Westley Martínez wrote:
On Fri, Apr 22, 2011 at 10:08:20AM -0400, Mel wrote:
[ ... ]
But sys.exit() doesn't return a string. My fave is
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
import sys
a = int (input ('enter a number '))
enter a number sys.setrecursionlimit(1)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
[ ... ]
What?
I guess sys.setrecursionlimit was meant to be called with a large number.
Calling it with a small one roadblocks the interpreter. Luckily, there can
be just enough room to call setrecursionlimit again with something
reasonable to get it all back. Not enough room for `eval
(sys.setrecursionlimit (2000)`, though.
Mel.
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Re: learnpython.org - an online interactive Python tutorial
harrismh777 wrote: Heiko Wundram wrote: The difference between strong typing and weak typing is best described by: Python 2.6.5 (r265:79063, Jun 12 2010, 17:07:01) [GCC 4.3.4 20090804 (release) 1] on cygwin Type help, copyright, credits or license for more information. 1+'2' Traceback (most recent call last): File stdin, line 1, inmodule TypeError: unsupported operand type(s) for +: 'int' and 'str' Yes. And you have managed to point out a serious flaw in the overall logic and consistency of Python, IMHO. Strings should auto-type-promote to numbers if appropriate. Appropriate is the problem. This is why Perl needs two completely different kinds of comparison -- one that works as though its operands are numbers, and one that works as though they're strings. Surprises to the programmer who picks the wrong one. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
Westley Martínez wrote:
On Fri, Apr 22, 2011 at 04:49:19PM +1000, Chris Angelico wrote:
U NO. NO NO NO. What if someone enters os.exit() as their
number? You shouldn't eval() unchecked user input!
Chris Angelico
Right, there's no way to check you're getting a number, however using:
a = int(input('enter a number ')) # use float() for floats
will raise an exception if it can't convert the string.
But sys.exit() doesn't return a string. My fave is
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
import sys
a = int (input ('enter a number '))
enter a number sys.setrecursionlimit(1)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Error in sys.excepthook:
RuntimeError: maximum recursion depth exceeded
Original exception was:
Traceback (most recent call last):
File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded while calling a Python object
int (0)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Error in sys.excepthook:
RuntimeError: maximum recursion depth exceeded
Original exception was:
Traceback (most recent call last):
File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded while calling a Python object
Mel.
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Re: List comprehension vs filter()
Chris Angelico wrote: On Wed, Apr 20, 2011 at 5:16 PM, Tim Roberts t...@probo.com wrote: You can solve this through the common lamba idiom of a closure: lst=filter(lambda x,posttype=posttype: x[type].lower()==posttype,lst) Seems a little odd, but sure. I guess this means that a function's default arguments are evaluated in the parent context, but the body is evaluated in its own context? The operation of calling a function has to evaluate arguments provided in the caller's namespace and assign them to variables in the called function's namespace. Yes. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: dictionary size changed during iteration
Laszlo Nagy wrote:
Given this iterator:
class SomeIterableObject(object):
def __iter__(self):
ukeys = self.updates.keys()
for key in ukeys:
if self.updates.has_key(key):
yield self.updates[key]
for rec in self.inserts:
yield rec
How can I get this exception:
RuntimeError: dictionary changed size during iteration
It is true that self.updates is being changed during the iteration. But
I have created the ukeys variable solely to prevent this kind of
error. Here is a proof of correctness:
d = {1:1,2:2}
k = d.keys()
del d[1]
k
[1, 2]
k is d.keys()
False
So what is wrong with this iterator? Why am I getting this error message?
`ukeys` isn't a different dictionary from `self.updates.keys` I'ts merely
another name referring to the same dict object. I think
ukeys = dict (self.updates.keys)
would do what you want.
Mel.
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Re: dictionary size changed during iteration
Mel wrote: Laszlo Nagy wrote: `ukeys` isn't a different dictionary from `self.updates.keys` I'ts merely another name referring to the same dict object. I think ukeys = dict (self.updates.keys) would do what you want. Sorry. Belay that. Thought I'd had enough coffee. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Feature suggestion -- return if true
Paul Rubin wrote: zildjohn01 zildjoh...@gmail.com writes: _temp = expr if _temp: return _temp I'm trying to figure out a context where you'd even want that, and I'm thinking that maybe it's some version of a repeat-until loop? Python doesn't have repeat-until and it's been proposed a few times. I can imagine return? tree_node.left return? tree_node.right although my real code would probably be more like if tree_node.left is not None: return left, tree_node.left if tree_node.right is not None: return right, tree_node.right where adding the left and right markers makes the return? feature impossible to use. The proposed feature reminds me of the `zod` function (was that the actual name?) that returned 0 rather than bringing on a ZeroDivideError. It would cement a strange corner-case into the language. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Argument of the bool function
Chris Angelico wrote:
Who would use keyword arguments with a function that takes only one arg
anyway?
It's hard to imagine. Maybe somebody trying to generalize function calls
(trying to interpret some other language using a python program?)
# e.g. input winds up having the effect of ..
function = bool
name = 'x'
value = 'the well at the end of the world'
## ...
actions.append ((function, {name:value}))
## ...
for function, args in actions:
results.append (function (**args))
Not something I, for one, do every day. But regularity in a language is
good when you can get it, especially for abstract things like that.
I can sort of guess that `dir` was perhaps coded in C for speed and doesn't
spend time looking for complicated argument lists.
Python is a pragmatic language, so all the rules come pre-broken.
Mel.
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Re: Argument of the bool function
candide wrote: About the standard function bool(), Python's official documentation tells us the following : bool([x]) Convert a value to a Boolean, using the standard truth testing procedure. In this context, what exactly a value is referring to ? For instance, x=42 bool(x=5) True Cute. What's happening here is that `x=5` isn't really an expression. It's passing a value to the named parameter `x`, specified in the definition of `bool`. Try it with something else: Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. bool(y=5) Traceback (most recent call last): File stdin, line 1, in module TypeError: 'y' is an invalid keyword argument for this function Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: [OT] Free software versus software idea patents
harrismh777 wrote: Steven D'Aprano wrote: At this point Microsoft has absolutely nothing to offer the computer science community at large except bzillions of euros ( or dollars ) of wasteful litigation and head-ache. Do you have an example of this wasteful litigation? You have to be kidding, right? Check *any* of the sites I listed above and read about it... software idea patent litigation is a business now worth billions of dollars per year. One of the premier sites: http://www.groklaw.net/ Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: is python 3 better than python 2?
neil wrote: what are the advantages? if it wasn't for python 3 breaking backwards compatibility would it be the better choice? IMHO the killer app for Python 3 is in more reasonable support for foreign character sets (no matter where your are, at least one out of the hundred-odd Unicode character sets is going to be foreign,) and generally internationalized data processing. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: iterable argument required
Νικόλαος Κούρας wrote:
iam getting the following error which i dont understand
**
163 # insert guest comments into database if form was
submitted
164 if @ in mail and comment not in (Σχολιάστε ή ρωτήστε
με σχετικά, ):
165 try:
166 cursor.execute( '''INSERT INTO
users(mail, comment) VALUES(%s, %s)''', (mail, comment) )
mail = None, comment = None
TypeError: iterable argument required
args = ('iterable argument required',)
In my original question can you explain to me what the meaning of the
following error is?
mail = None, comment = None
TypeError: iterable argument required
args = ('iterable argument required',)
*
Also i noticed that if i append a query string in the end of a url
with the varibble mail attached like
http://superhost.gr/hosting.html?mail=test
then page hosting.html does load without any problem.
If i remove the query string from the ned of the URL then i'am getting
the error message i posted.
So its not that the if condition is wrong but something happens with
the form variable 'mail' .
My wild guess is that the trouble is in `if @ in mail` . You can only
test somthing `in` something if the second thing is iterable. So when
you don't supply a value via `?mail=' -- maybe the code that sets the
value of `mail` from the URL (code you don't show us) sets `mail=None`,
your server-side code blows up. Things would be simpler if you included
a traceback in your error logging.
Mel.
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Re: send function keys to a legacy DOS program
Alexander Gattin wrote: Another thing is that you may need to send key release after key press in order for the application to trigger the F5/F2/F7 event. I'm not sure what the scan codes for F5/F2/F7 releases are, but think that they may be: F5: 0xBF F2: 0xBC F7: 0xC1 True. The key-release codes are the key-press codes (the key numbers) but with the high-order bit set. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Guido rethinking removal of cmp from sort method
Carl Banks wrote: On Mar 23, 1:38 pm, Paul Rubin no.em...@nospam.invalid wrote: Well, I thought it was also to get rid of 3-way cmp in general, in favor of rich comparison. Supporting both __cmp__ and rich comparison methods of a class does add a lot of complexity. The cmp argument of sort doesn't. The cmp argument doesn't depend in any way on an object's __cmp__ method, so getting rid of __cmp__ wasn't any good readon to also get rid of the cmp argument; their only relationship is that they're spelled the same. Nor is there any reason why cmp being a useful argument of sort should indicate that __cmp__ should be retained in classes. I would have thought that the upper limit of cost of supporting cmp= and key= would be two different internal front-ends to the internal internal sort. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bounds checking
Jean-Michel Pichavant wrote:
Martin De Kauwe wrote:
Don't check for bounds, fix any bug in the code that would set your
values out of bounds and use asserts while debugging.
[ ... ]
def __setattr__(self, attribute, value):
if not self.funcTable.get(attribute, lambda x: True)(value):
sys.exit('error out of bound')
return object.__setattr(self, attribute, value)
Offhand, my only quibble is that sys.exit is not helpful for debugging.
Much better to raise an error:
if not self.funcTable.get(attribute, lambda x: True)(value):
raise ValueError ('error out of bound')
or define a subclass of ValueError just for this purpose. On error, the
program will stop just as dead, but you'll get a trace.
Mel.
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Re: Coding and Decoding in Python
Wanderer wrote:
I have a dll that to communicate with I need to send numeric codes. So
I created a dictionary. It works in one direction in that I can
address the key and get the value. But when the program returns the
value I can't get the key. This code is very simple and I could use a
list and the index except for the last value. Is there a better way to
handle coding and decoding values to strings?
QCam_Info = {
'qinfCameraType' : 0,# Camera model (see
QCam_qcCameraType)
'qinfSerialNumber': 1,# Deprecated
'qinfHardwareVersion' : 2,# Hardware version
'qinfFirmwareVersion' : 3,# Firmware version
'qinfCcd' : 4,# CCD model (see
QCam_qcCcd)
[ ... ]
'_qinf_force32' : 0x
}
I handled this problem in a kind of cheap, nasty way with (untested)
for k, v in QCam_Info.items():
QCam_Info[v] = k
Then the dictionary lookups work both ways.
Mel.
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Re: PEP for module naming conventions
Tim Johnson wrote: I need to be better informed on naming conventions for modules. For instance, I need to create a new module and I want to make sure that the module name will not conflict with any future or current python system module names. COBOL in its golden years had a practice that reserved words were almost never hyphenated -- the few that were could be counted on the fingers of perhaps four hands and were mostly required paragraph names that were always used and hard to forget. It might turn out well to specify that system module names will never contain more than, say, one underscore. That way, nice descriptive application module names like 'analyzer_tool_utils' and such would always be safe to use. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: my computer is allergic to pickles
Bob Fnord wrote: I want a portable data file (can be moved around the filesystem or copied to another machine and used), so I don't want to use mysql or postgres. I guess the sqlite approach would work, but I think it would be difficult to turn the tuples of strings and lists of strings and numbers into database table lines. This is as hairy as it's ever got for me (untested): def inserter (db, table_name, names, values): query = 'INSERT INTO %s (%s) VALUES (%s)' % (table_name, ','.join (names), ','.join (['?'] * len (names))) cur = db.cursor() cur.execute (query, values) cur.close() #... for v in all_value_triples: inserter (db, 'some_table', ['f1', 'f2', 'f3'], v) (or even write a bulk_inserter that took all_value_triples as an argument and moved the `for v in ...` inside the function.) Would a database in a file have any advantages over a file made by marshal or shelve? Depends. An sqlite3 database file is usable by programs not written in Python. I'm more worried about the fact that a python program in user space can bring down the computer! Never been a problem in the programs I've written. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: ImSim: Image Similarity
n00m wrote: But funny thing takes place. At first thought it's a false-positive: some modern South East Asian town and a lake somewhere in Russia, more than 100 years ago. Nothing similar in them? On both pics we see: -- a lot of water on foreground; -- a lot of blue sky at sunny mid-day; -- a bit of light white clouds in the sky; In short, the notion of similarity can be speculated about just endlessly. Exactly. That's the kind of similarity I would call valid. That's what my algorithms, if I ever finished writing any, would be looking for. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: ImSim: Image Similarity
n00m wrote:
I uploaded a new version of the subject with a
VERY MINOR correction in it. Namely, in line #55:
print '%12s %7.2f' % (db[k][1], db[k][0] / 3600.0,)
instead of
print '%12s %7.2f' % (db[k][1], db[k][0] * 0.001,)
I.e. I normalized it to base = 100.
Now the values of similarity can't be greater than 100
and can be treated as some regular percents (%%).
Also, due to this change, the *empirical* threshold of
system alarmity moved down from number 70 to 20%.
bears2.jpg
bears2.jpg0.00
bears3.jpg 15.37
bears1.jpg 19.13
sky1.jpg 23.29
sky2.jpg 23.45
ff1.jpg 25.37
lake1.jpg 26.43
water1.jpg 26.93
ff2.jpg 28.43
roses1.jpg 31.95
roses2.jpg 36.12
I'd like to see a *lot* more structure in there, with modularization, so the
internal functions could be used from another program. Once I'd figured out
what it was doing, I had this:
from PIL import Image
from PIL import ImageStat
def row_column_histograms (file_name):
'''Reduce the image to a 5x5 square of b/w brightness levels 0..3
Return two brightness histograms across Y and X
packed into a 10-item list of 4-item histograms.'''
im = Image.open (file_name)
im = im.convert ('L') # convert to 8-bit b/w
w, h = 300, 300
im = im.resize ((w, h))
imst = ImageStat.Stat (im)
sr = imst.mean[0] # average pixel level in layer 0
sr_low, sr_mid, sr_high = (sr*2)/3, sr, (sr*4)/3
def foo (t):
if t sr_low: return 0
if t sr_mid: return 1
if t sr_high: return 2
return 3
im = im.point (foo) # reduce to brightness levels 0..3
yhist = [[0]*4 for i in xrange(5)]
xhist = [[0]*4 for i in xrange(5)]
for y in xrange (h):
for x in xrange (w):
k = im.getpixel ((x, y))
yhist[y / 60][k] += 1
xhist[x / 60][k] += 1
return yhist + xhist
def difference_ranks (test_histogram, sample_histograms):
'''Return a list of difference ranks between the test histograms and
each of the samples.'''
result = [0]*len (sample_histograms)
for k, s in enumerate (sample_histograms): # for each image
for i in xrange(10):# for each histogram slot
for j in xrange(4): # for each brightness level
result[k] += abs (s[i][j] - test_histogram[i][j])
return result
if __name__ == '__main__':
import getopt, sys
opts, args = getopt.getopt (sys.argv[1:], '', [])
if not args:
args = [
'bears1.jpg',
'bears2.jpg',
'bears3.jpg',
'roses1.jpg',
'roses2.jpg',
'ff1.jpg',
'ff2.jpg',
'sky1.jpg',
'sky2.jpg',
'water1.jpg',
'lake1.jpg',
]
test_pic = 'bears2.jpg'
else:
test_pic, args = args[0], args[1:]
z = [row_column_histograms (a) for a in args]
test_z = row_column_histograms (test_pic)
file_ranks = zip (difference_ranks (test_z, z), args)
file_ranks.sort()
print '%12s' % (test_pic,)
print ''
for r in file_ranks:
print '%12s %7.2f' % (r[1], r[0] / 3600.0,)
(omitting a few comments that wrapped around.) The test-case still agrees
with your archived version:
mwilson@tecumseth:~/sandbox/im_sim$ python image_rank.py bears2.jpg *.jpg
bears2.jpg
bears2.jpg0.00
bears3.jpg 15.37
bears1.jpg 19.20
sky1.jpg 23.20
sky2.jpg 23.37
ff1.jpg 25.30
lake1.jpg 26.38
water1.jpg 26.98
ff2.jpg 28.43
roses1.jpg 32.01
I'd vaguely wanted to do something like this for a while, but I never dug
far enough into PIL to even get started. An additional kind of ranking that
takes colour into account would also be good -- that's the first one I never
did.
Cheers, Mel.
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