Mailman 3 March 2015 - Python-Dev

PiCxx
by π March 25, 2015

March 25, 2015

Hello PythonDevvers, I apologise in advance. This is slightly off topic. This will be my only post on the subject. PyCXX (http://sourceforge.net/projects/cxx/ <http://sourceforge.net/projects/cxx/>) accomplishes roughly the same as Boost::Python (C++ wrapper for CPython), only without requiring Boost. The original code has become tangled and bloated. Over the winter I've rewritten it using C++11. New C++11 features have allowed for more direct/compact/concise/readable code. I've … [View More]

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How is obmalloc safe with "Invalid read of size 4" ?
by Karl Pickett March 24, 2015

March 24, 2015

We are having random, rare, nonreproducible segfaults/hangs with python2 on ubuntu 14.04 in EC2. I've managed to attach GDB to some hung ones and there looks like clear memory corruption in the 'interned' hash table, causing lookdict_string() to spin forever because all remaining slots have a garbage 'key' pointer. This happens just loading the 'site' module dependencies, like 're' or 'codecs', before any of our code even gets run. So we then tried running it under valgrind, and we got a lot … [View More]

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Re: [Python-Dev] cpython: #23657 Don't explicitly do an isinstance check for str in zipapp
by Serhiy Storchaka March 24, 2015

March 24, 2015

On 22.03.15 17:33, paul.moore wrote: > https://hg.python.org/cpython/rev/0b2993742650 > changeset: 95126:0b2993742650 > user: Paul Moore <p.f.moore(a)gmail.com> > date: Sun Mar 22 15:32:36 2015 +0000 > summary: > #23657 Don't explicitly do an isinstance check for str in zipapp > > As a result, explicitly support pathlib.Path objects as arguments. > Also added tests for the CLI interface. Congratulate with your first commit Paul!

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--with-valgrind and --enable-shared
by Andrea Griffini March 24, 2015

March 24, 2015

Hello, does it have any sense for a linux distribution (arch to be specific) to provide default Python package compiled with valgrind support? I thought this flag was just about silencing false positives generated by valgrind (in other words a workaround for "bugs" of another software) and useful only when developing Python itself or C extensions. The same distribution also compiles by default to a shared library and this has a quite noticeable impact on performance on x64 (surprisingly for … [View More]

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Installing Python to non-ASCII paths
by Paul Moore March 23, 2015

March 23, 2015

Something that hit me today, which might become a more common issue when the Windows installers move towards installing to the user directory, is that there appear to be some bugs in handling of non-ASCII paths. Two that I spotted are a failure of the "script wrappers" installed by pip to work with a non-ASCII interpreter path (reported to distlib) and a possible issue with the py.exe launcher when a script has non-ASCII in the shebang line (not reported yet because I'm not clear on what's … [View More]

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some minor questions about pep8
by Lewis Coates March 23, 2015

March 23, 2015

In pep8 there are two conflicting statements, both https://www.python.org/dev/peps/pep-0008/#version-bookkeeping https://www.python.org/dev/peps/pep-0008/#imports Stipulate that they should be "at the top of the file after any module comments and docstrings." Which of these takes precedence? Secondly, we also have an "__author__", and "__project__" variables, I assume these would be put with the version information as well?

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Re: [Python-Dev] Request for comments: [issue22941] IPv4Interface arithmetic changes subnet mask
by Søren Løvborg March 23, 2015

March 23, 2015

Thanks for the feedback, and apologies for my late reply. I have to say, I'm not entirely sold on the argument for raising an exception on subnet "overflow". First, I'll note what happens if we overflow an IPv4Address: >>> ipaddress.IPv4Address('255.255.255.255') + 1 Traceback (most recent call last): ... ipaddress.AddressValueError: 4294967296 (>= 2**32) is not permitted as an IPv4 address Now, I used "IPv4Interface() + 1" to mean "Give me the IP next … [View More]

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0-base and 1-base indexed iterables? Custom slicing rules?
by pedro santos March 22, 2015

March 22, 2015

Hi, I'm an Art and CG student learning Python and today's exercise was about positions in a tiled room. The fact that I had to check if a position was inside the room and given that in a 1x1 room, 0.0 was considered in and 1.0 was considered out, it kept me thinking about 0-base indexing iterables and slicing. Read some articles and discussions, some pros and cons to each 0-base and 1-base, concerns about slicing, etc. But ultimately the question that got stuck in me and didn't found an answer … [View More]was: Why can't both 0-base and 1-base indexing exist in the same language, and why can't slicing be customized? If I'm indexing the ruler marks, intervals, boundaries, dots, makes sense to start of at 0; rul=[0,1,2,3,4,5,6] would index every mark on my ruler so that accordingly rul[0]=0, rul[5]=5. If I'm indexing the blue circles, natural number quantities, objects, spans, makes sense to start at 1; cir= [1,2,3,4,5] so that cir[1]=1 and cir[5]=5. Now, a lot of the discussion was to do with slicing coupled with the indexing and I don't totally understand why. a ≤ x < b is not so intuitive when dealing with objects ("I want balls 1 up to the the one before 3"), so on one side, you put the finger on what you want and on the other, on what you don't want. But this method does have the neat property of producing neighbor selections that border perfectly, as in [:a][a:b][b:c]. Although in inverse order(-1), the results can be unexpected as it returns values off-by-one from its counterpart like; L=[0,1,2,3,4,5] so that L[1:3]=[1,2] and L[3:1:-1]=[3:2]. So it's consistent with the rule a ≤ x < b, grabbing the lower limit item, but it can feel strange by not producing the same selection with inverse order. a ≤ x ≤ b is a natural way to select objets ("I want the balls 1 up to 3"), so you're putting the finger on the things you want. If you inverse the order(-1) it's still very easy to grasp what are you picking because whatever you select it's included like: L=[0,1,2,3,4,5] so that L[1:3]=[1,2,3] and L[3:1:-1]=[3,2,1]. Problems seem to arrive though, when trying to do neighbor selections, where one would have to do [:a][a+1:b][b+1:c] to have the border perfectly. That terrible? Even though one could see a ≤ x < b to be more adept to 0-base, and a ≤ x ≤ b to be more adept to 1-base, the way I see it, index base and slicing rules could be somehow independent. And one would index and slice the way it would fit the rationale of the problem or the data, because even slicing a 1-base indexed array with a ≤ x < b, would still produce an expected outcome, as in cir=[1,2,3,4,5] so that cir[1:3]=[1,2] or cir[:3]=[1,2]. Same thing applying a ≤ x ≤ b to a 0-base indexed array, as in rul[0,1,2,3,4,5] so that rul[:2]=[0,1,2] or rul[0:2]=[0,1,2]. Given that python is an example of human friendly code language, emphasizing readability, wouldn't having 0 and 1 base indexing and custom slicing methods, improve the thought process when writing and reading the code, by fitting them better to specific contexts or data? Is there some language that provides both or each language picks only one? Cheers -- *------------------------------[image: http://i153.photobucket.com/albums/s202/animatics/probiner-sig.gif]Pedro Alpiarça dos Santos Animator 3DModeler Illustrator >> http://probiner.x10.mx/ <http://probiner.x10.mx/>* [View Less]

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How to document functions with optional positional parameters?
by Serhiy Storchaka March 22, 2015

March 22, 2015

How to document functions with optional positional parameters? For example binascii.crc32(). It has two positional parameters, one is mandatory, and one is optional with default value 0. With Argument Clinic its signature is crc32(data, crc=0, /). In the documentation it is written as crc32(data[, crc]) (and noted that the default value of the second parameter is 0). Both are not valid Python syntax. Can the documentation be change to crc32(data, crc=0)? Related issues: https://bugs.… [View More]

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Re: [Python-Dev] Missing *-unpacking generalizations (issue 2292)
by Neil Girdhar March 22, 2015

March 22, 2015

Wow, this is an excellent review. Thank you. My only question is with respect to this: I think there ought to be two opcodes; one for unpacking maps in function calls and another for literals. The whole function location thing is rather hideous. What are the two opcodes? BUILD_MAP_UNPACK and BUILD_MAP_UNPACK_WITH_CALL? The first takes (n) a number of maps that it will merge, and the second does the same but also accepts (function_call_location) for the purpose of error reporting? Thanks, … [View More]

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