Mailman 3 July 2018 - Python-ideas

Including the unparse module in the standard library
by Andre Roberge July 16, 2018

July 16, 2018

In the cPython repository, there is an unparse module in the Tools section. https://github.com/python/cpython/blob/master/Tools/parser/unparse.py However, as it is not part of the standard library, it cannot be easily used; to do so, one needs to make a local copy in a place from where it can be imported. This module can be useful for people using the ast module to create and parse trees, modify them ... and who want to convert the result back into source code. Since it is obviously … [View More]

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Do not block threads when pickle/unpickle
by Martin Bammer July 16, 2018

July 16, 2018

Hi, the old and slow python implementation of pickle didn't block background thread. But the newer C-implementation blocks other threads while dump/load is running. Wouldn't it be possible to allow other threads during this time? Especially could load/loads release the GIL, because Python objects are not available to the Python code until these functions have finished? Regards, Martin

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Unicode Name Aliases keyword argument abbreviation in unicodedata.name for missing names
by Robert Vanden Eynde July 15, 2018

July 15, 2018

unicodedata.name<http://unicodedata.name> raises KeyError for a few unicode characters like '\0' or '\n', altough the documentation is very clear on the implementation, this is often not what people want, ie. a string describing the character. In Python 3.3, the name aliases became accepted in unicodedata.lookup('NULL') and '\N{NULL}' == '\N{NUL}'. One could expect that lookup(name(x)) == x for all unicode character but this property doesn't hold because of the few characters that do … [View More]

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Re: [Python-ideas] Add the imath module
by Jeroen Demeyer July 14, 2018

July 14, 2018

On 2018-07-12 20:11, Steven D'Aprano wrote: > about 4.7 seconds to test 2**800 + 1; In SageMath: sage: n = 2**800+1; timeit('is_prime(n)') 625 loops, best of 3: 303 µs per loop That's 4 orders of magnitude faster...

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Make import an expression
by Ken Hilton July 14, 2018

July 14, 2018

Hi all, Just a curious idea I had. The subject says it all. "import" is currently a statement, which means it cannot be used inside anything else. Currently, the only way to import a module inside an expression is to use the __import__ function, which is both cumbersome and takes up more space (which is disadvantageous in things like code golf). I propose making "import" an expression, thus allowing the syntactic sugar of "import module" -> "__import__('module')" to be graduated to the … [View More]

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Re: [Python-ideas] Add the imath module
by Jeroen Demeyer July 13, 2018

July 13, 2018

On 2018-07-13 14:11, Steven D'Aprano wrote: > What it *actually* does is: > > is_almost_certainly_prime_except_for_a_ludicrously_microscopic_chance_of_error_thousands_of_times_less_likely_than_a_stray_cosmic_ray_flipping_a_bit_in_memory_and_causing_the_wrong_result_to_be_returned() That's just a long variant of is_probable_prime() > If your bank is satisfied with "mere probable prime number" to transfer > billions of dollars around the world, then I'm sure that the users of … [View More]

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Fwd: grouping / dict of lists
by David Mertz July 13, 2018

July 13, 2018

Steven: You've misunderstood part of the discussion. There are two different signatures being discussed/proposed for a grouping() function. The one you show we might call grouping_michael(). The alternate API we might call grouping_chris(). These two calls will produce the same result (the first output you show) grouping_michael(words, keyfunc=len) grouping_chris((len(word), word) for word in words) I happen to prefer grouping_michael(), but recognize they each make slightly different … [View More]

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Re: [Python-ideas] Add the imath module
by Jeroen Demeyer July 13, 2018

July 13, 2018

On 2018-07-13 04:02, Chris Angelico wrote: > Haha. Okay. I'm not familiar with every possible primality test, so I > had no idea that they ALL have the same failure mode :) There exist guaranteed primality tests, but those are much slower and more complicated. The state of the art is ECPP: https://en.wikipedia.org/wiki/Elliptic_curve_primality

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Re: [Python-ideas] Add the imath module
by Jeroen Demeyer July 13, 2018

July 13, 2018

On 2018-07-13 14:26, Steven D'Aprano wrote: > I'm pretty sure that Sage is using numpy This computation uses PARI/GP, a dedicated library for number theory (https://pari.math.u-bordeaux.fr/) with a Python interface (https://github.com/defeo/cypari2). > And it's > probably making far less conservative choices about the rate of false > positives it is willing to accept. It's an actual primality test, not a probable primality test. But for numbers which are not prime (like your … [View More]

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Re: [Python-ideas] Add the imath module
by Jeroen Demeyer July 13, 2018

July 13, 2018

On 2018-07-13 11:50, Jacco van Dorp wrote: > At the very least, use is_likely_prime() as function name. I agree with you here: the function name should reflect what it actually does. (Note that the technical term is "probable prime", so it should be is_probable_prime) But I don't think that the Python stdlib should have a proven is_prime() function because that would be complicated, slow and have very limited benefit over is_probable_prime().

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