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Clarify that the itertools pure python equivalents are only approximate. #70114

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tfeldmann mannequin opened this issue Dec 22, 2015 · 10 comments
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Clarify that the itertools pure python equivalents are only approximate. #70114

tfeldmann mannequin opened this issue Dec 22, 2015 · 10 comments
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@rhettinger
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docs Documentation in the Doc dir type-bug An unexpected behavior, bug, or error

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@tfeldmann
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tfeldmann mannequin commented Dec 22, 2015

BPO 25926
Nosy @rhettinger, @bitdancer, @tfeldmann, @Shredder13
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  • issue25926.diff: diff for change in itertools.rst
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    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = 'https://github.com/rhettinger'
closed_at = <Date 2016-05-28.07:27:44.876>
created_at = <Date 2015-12-22.17:40:36.188>
labels = ['type-bug', 'docs']
title = 'Clarify that the itertools pure python equivalents are only approximate.'
updated_at = <Date 2016-05-28.11:26:07.030>
user = 'https://github.com/tfeldmann'

    bugs.python.org fields:

    activity = <Date 2016-05-28.11:26:07.030>
actor = 'python-dev'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2016-05-28.07:27:44.876>
closer = 'rhettinger'
components = ['Documentation']
creation = <Date 2015-12-22.17:40:36.188>
creator = 'tfeldmann'
dependencies = []
files = ['43026']
hgrepos = ['344', '345']
issue_num = 25926
keywords = ['patch']
message_count = 10.0
messages = ['256847', '256848', '265835', '265840', '266478', '266480', '266542', '266543', '266544', '266547']
nosy_count = 6.0
nosy_names = ['rhettinger', 'r.david.murray', 'python-dev', 'Winterflower', 'tfeldmann', 'Nofar Schnider']
pr_nums = []
priority = 'low'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue25926'
versions = ['Python 2.7', 'Python 3.5']
    @tfeldmann
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    tfeldmann mannequin commented Dec 22, 2015

    According to the docs itertools.repeat(object[, times]) is equivalent to

    def repeat(object, times=None):
    # repeat(10, 3) --> 10 10 10
    if times is None:
        while True:
            yield object
    else:
        for i in range(times):
            yield object

    But it raises a TypeError when used this way:

    Python 3.5.1 (default, Dec 10 2015, 10:34:07)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.1.76)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from itertools import repeat
>>> repeat('x', times=None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object cannot be interpreted as an integer

    The times keyword can be omitted but not explicitly set to None.
    I checked with Python Versions 2.7 and 3.5.1 on Mac OS X and Windows 10.

    @tfeldmann tfeldmann mannequin added interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error labels Dec 22, 2015
    @bitdancer
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    Huh. I always thought the wording was "roughly equivalent to". This is a consequence of C vs python, and is the reason the docstring uses the [] notation.

    @Winterflower
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    Winterflower mannequin commented May 18, 2016

    Should 'roughly equivalent to' be added as a note to the docs?

    @rhettinger
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    I'm okay with changing the docs to "roughly equivalent to". That will help prevent the occasional misreading as "precisely equivalent in every respect".

    @Shredder13
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    Shredder13 mannequin commented May 27, 2016

    Issue bpo-25926
    Changed all "equivalent to" occurrences to "roughly equivalent to"

    @Shredder13
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    Shredder13 mannequin commented May 27, 2016

    Attached a diff
    All occurrences of "equivalent to" are switched to "roughly equivalent to"

    @python-dev
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    python-dev mannequin commented May 28, 2016

    New changeset 613314c3f9ed by Raymond Hettinger in branch '3.5':
    bpo-25926: Clarify that the pure python equivalents are only approximate.
    https://hg.python.org/cpython/rev/613314c3f9ed

    New changeset e67e970de54a by Raymond Hettinger in branch 'default':
    bpo-25926: Clarify that the pure python equivalents are only approximate.
    https://hg.python.org/cpython/rev/e67e970de54a

    @python-dev
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    python-dev mannequin commented May 28, 2016

    New changeset f66c30f66235 by Raymond Hettinger in branch '2.7':
    bpo-25926: Clarify that the pure python equivalents are only approximate.
    https://hg.python.org/cpython/rev/f66c30f66235

    @rhettinger
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    Nofar, thanks for the patch.

    @rhettinger rhettinger added docs Documentation in the Doc dir and removed interpreter-core (Objects, Python, Grammar, and Parser dirs) labels May 28, 2016
    @rhettinger rhettinger changed the title problems with "times" keyword in itertools.repeat Clarify that the itertools pure python equivalents are only approximate. May 28, 2016
    @python-dev
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    python-dev mannequin commented May 28, 2016

    New changeset 35fa2ec1f237 by Serhiy Storchaka in branch 'default':
    Merge heads (issue bpo-25926).
    https://hg.python.org/cpython/rev/35fa2ec1f237

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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