Mailman 3 January 2015 - Python-ideas

Adding `pathlib.Path` method that would send file to recycle bin
by Ram Rachum Jan. 7, 2015

Jan. 7, 2015

Hi guys, I want to have a method of `pathlib.Path` that would send a file to the recycle bin. (i.e. soft delete.) What do you think about adding this? I see there's a PyPI package `Send2Trash` that does this, but it would be nice if this was in the standard library. Thanks, Ram.

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Possible new itertool: comm()
by Paul Moore Jan. 7, 2015

Jan. 7, 2015

In writing a utility script today, I found myself needing to do something similar to what the Unix "comm" utility does - take two sorted iterators, and partition the values into "only in the first", "only in the second", and "in both" groups. I couldn't find an obvious implementation around, so I ended up having to write my own (see below). Would this be something useful to add to the itertools module? The reasons I think it might be worth including in the stdlib are: 1. The implementation is somewhat tricky to get right, especially the edge cases (I'm not 100% sure my implementation is completely right in this regard). So implementing it yourself each time is error-prone and time consuming. 2. The times I've needed this have been ad-hoc scripts (I'm on Windows, so while a Unix user might use a quick shell pipeline with comm, that's less convenient for me) where depending on a 3rd party distribution from PyPI is less ideal. There's plenty of room for API bikeshedding here, but the basic algorithm remains the same. What do people think? Paul def comm(it1, it2): """Partition 2 sorted iterators into common, only in 1st, and only in 2nd. >>> list(comm([1,2,3], [2,3,4])) [('<', 1), ('=', 2), ('=', 3), ('>', 4)] >>> list(comm([0,1,2,3], [2,3,4,5])) [('<', 0), ('<', 1), ('=', 2), ('=', 3), ('>', 4), ('>', 5)] >>> list(comm([0,1,2,3,6], [2,3,4,5])) [('<', 0), ('<', 1), ('=', 2), ('=', 3), ('>', 4), ('>', 5), ('<', 6)] >>> list(comm([0,1], [])) [('<', 0), ('<', 1)] >>> list(comm([], [0,1])) [('>', 0), ('>', 1)] >>> list(comm([0,1], [0,1])) [('=', 0), ('=', 1)] >>> list(comm([], [])) [] """ it1 = iter(it1) it2 = iter(it2) it1_finished = False it2_finished = False try: v1 = next(it1) except StopIteration: it1_finished = True try: v2 = next(it2) except StopIteration: it2_finished = True while not (it1_finished or it2_finished): if v1 < v2: yield ('<', v1) try: v1 = next(it1) except StopIteration: it1_finished = True elif v1 > v2: yield ('>', v2) try: v2 = next(it2) except StopIteration: it2_finished = True else: yield ('=', v1) try: v1 = next(it1) except StopIteration: it1_finished = True try: v2 = next(it2) except StopIteration: it2_finished = True if it1_finished and not it2_finished: yield ('>', v2) for v2 in it2: yield ('>', v2) if it2_finished and not it1_finished: yield ('<', v1) for v1 in it1: yield ('<', v1) if __name__ == '__main__': import doctest doctest.testmod()

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build:// Path / URI / URN with the __div__ operator
by Wes Turner Jan. 7, 2015

Jan. 7, 2015

* [ ] build Path / URI / URN with the __div__ operator * [ ] pick some combination of operators for URI schema, query, fragment conjunction (like URLObject.with_<*>):: # scheme://user@host.netloc:port/path/?query#fragment from _ import URI, https, //, http https // 'user@host.netloc:port' / path ** query % fragment * __div__ / * __floordiv__ // * __and__ && * __mod__ % * __invert__ ~ * __or__ | * __xor__ ^ * __and__ + * __mul__ * * __pow__ ** * __lshift__ << * __rshift__ >> References ----------------- * https://pypi.python.org/pypi/path.py -- __div__ * https://pypi.python.org/pypi/pathlib -- [ Standard Library ] * https://pypi.python.org/pypi/furl * https://pypi.python.org/pypi/URLObject - [ with_scheme, with_netloc, with_path, ... ] * https://urlobject.readthedocs.org/en/latest/quickstart.html * https://pypi.python.org/pypi/rdflib

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inspect.getclassdistance
by Alexis Lee Jan. 5, 2015

Jan. 5, 2015

Hopefully sufficiently documented to stand without introduction: def getclassdistance(srcs, dst): """srcs may be either a single class or a list of (class, distance) pairs. dst is the superclass to find. Performs a breadth-first search for dst, returning the shortest distance. """ if type(srcs) != list: srcs = [(srcs, 0)] if len(srcs) == 0: return None here, distance = srcs[0] if here == dst: return distance newSrc = srcs[1:] + [(c, distance + 1) for c in list(here.__bases__)] return classDistance(newSrc, dst) If this is already implemented and I just couldn't find it, I'm more than happy to withdraw the idea. Alexis -- Nova Engineer, HP Cloud. AKA lealexis, lxsli.

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Slicing and Chainging iterables.
by yotam vaknin Jan. 4, 2015

Jan. 4, 2015

I would like to purpose that in python 3 it will be easy to chain and slice Iterators just like you can add and slice lists and tuples easily. I think there could be 2 methods to do this: 1. Implementing '+' and slicing ([1:2:3]) for iterators and generators by default, Resulting in Itertool's chain(a,b) and islice(a,b,c) respectively. 2. Having itertool's chain and islice imported by default. I think since python 3 return zip,map, dict.items and so on as iterators, it makes working with those kind of objects more difficult without having these methods around. And since those methods are important enough to have for lists, it seems important enough for iterators too.

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