Mailman 3 February 2017 - Python-ideas

__repr__: to support pprint
by 语言破碎处 March 1, 2017

March 1, 2017

Hi, everyone! Oftenly, __repr__ return "{type}({args}, {kws})" problem: 1) to call .format() myself is tedious I have seen someone do it wrong: "T(1,)"! I write a helper function myself, but to import such tiny function everywhere isnot good. 2) pprint cannot dive into string that from repr() To use pprint, I sometimes have to recursively turn objects into builtin containers: (type_name, args...) solution: allow __repr__ to … [View More]

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Expose a child factory using MappingProxyType in builtins
by Michel Desmoulin March 1, 2017

March 1, 2017

We have the immutable frozenset for sets and and tuples for lists. But we also have something to manipulate dict as immutable datastructures: >>> from types import MappingProxyType as idict >>> d = idict({'a':1, 'b':2, 'c':3}) >>> d['a'] = 4 Traceback (most recent call last): File "<ipython-input-3-c6f93d6278af>", line 1, in <module> d['a'] = 4 TypeError: 'mappingproxy' object does not support item assignment We could expose this as a built type … [View More]

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unify usage of mutable and immutable objects
by 语言破碎处 March 1, 2017

March 1, 2017

Hi! I write a '<'-based immutable set class. But it is quit different from the standard set class. I wish collections.abc.Set be more friendly to immutable tree sets or Python add new syntax to unify such difference. good example: a = [] a += a # "a" is the original list a = () a += a # "a" is a new tuple bad example: a = set() a.add(1) # return None; "a" changed e = a.pop(); a = frozen_tree_set() a = a.add(1) # return … [View More]

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Optional argument to fnmatch functions treat * and ** differently
by Aaron Feb. 28, 2017

Feb. 28, 2017

Hello, I would like fnmatch.fnmatch to have a mode where: ** matches any files and zero or more directories and subdirectories (i.e. the current behaviour of *) * matches in one path level/only to the next path separator This is essentially achievable in glob.glob from version 3.5 (with recursive=True), but glob is not suitable for my use case, as I need to work with strings and not files. I would like to gauge whether adding such behaviour behind an optional argument … [View More]

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Another use case for the 'lazy' (aka 'delayed') keyword
by Michel Desmoulin Feb. 28, 2017

Feb. 28, 2017

The debate on the 'lazy' keyword seems to have settled, but I don't know if somebody is trying to write a PEP about it. Anyway, I was doing something like this the other day: conf.get('setting_name', load_from_db('setting_name')) And then realized I could save a query not doing the load_from_db() call most of the time. But dict.get didn't accept callable so I couldn't do: conf.get('setting_name', lambda key: load_from_db('setting_name')) Which is standard practice in a lot of popular … [View More]

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math.nextafter
by Juraj Sukop Feb. 28, 2017

Feb. 28, 2017

Hello! Function `nextafter(x, y)` returns the next representable value of `x` in the direction of `y`, and if `x` equals to `y`, `y` is returned. [1] It is useful for incrementing/decrementing floating-point number by the smallest amount possible or for testing if two numbers are closest to each other without being the same. The following snippet written by Mark Dickinson emulates the functionality in pure Python [2]: import math import struct def next_up(x): # NaNs and … [View More]

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Make Path objects iterable
by Vamsi Krishna Avula Feb. 27, 2017

Feb. 27, 2017

This is somewhere between a question and a proposal. I'm just trying to understand why Path objects use an explicit iterdir method. Why not make them iterable? -- Vamsi

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if in for-loop statement
by Henk-Jaap Wagenaar Feb. 24, 2017

Feb. 24, 2017

Hi all, Often I have typed something like for x in range(100) if is_prime(x): # do things with x to find that this does not work, instead resorting to: for x in range(100): if is_prime(x): # do things with x or for x in range(100): if not is_prime(x): continue # do things with x Other solutions to another case of this 'problem' are discussed has been discussed on StackOverflow ( http://stackoverflow.com/questions/6981717/… [View More]

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Fwd: Define a method or function attribute outside of a class with the dot operator
by Markus Meskanen Feb. 24, 2017

Feb. 24, 2017

> > That saves one line, at the cost of introducing even more complexity to > the language. > > Are these use-cases common enough to justify the extra syntax? > Keep in mind that the extra syntax is *very* minor, and goes hand-to-hand with the existing attribute access syntax. Basically it's taking the existing syntax to one more place, where it in my opinion should have been since long ago. > What advantage does this proposed syntax have? > > Since that's not … [View More]

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Re: [Python-ideas] if in for-loop statement
by Régis Martin Feb. 23, 2017

Feb. 23, 2017

Hello, why not using the filter function? for x in filter(is_prime, range(100)): # do something with x This is equivalent as was mentionned at first: for x in range(100) if is_prime(x): # do things with x Régis -- Régis Martin Directeur de Projets Astek Industrie Tel: 06-83-53-15-05 http://www.groupeastek.com/

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