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Make PyNumber_Index() always returning an exact int instance #84969

serhiy-storchaka opened this issue May 27, 2020 · 4 comments

Make PyNumber_Index() always returning an exact int instance #84969

serhiy-storchaka opened this issue May 27, 2020 · 4 comments
3.10 interpreter-core type-feature


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@serhiy-storchaka serhiy-storchaka commented May 27, 2020

BPO 40792
Nosy @warsaw, @mdickinson, @serhiy-storchaka
  • #20443
  • 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 = None
    closed_at = <Date 2020-05-28.07:36:23.218>
    created_at = <Date 2020-05-27.07:57:47.257>
    labels = ['interpreter-core', 'type-feature', '3.10']
    title = 'Make PyNumber_Index() always returning an exact int instance'
    updated_at = <Date 2020-05-28.07:36:23.217>
    user = '' fields:

    activity = <Date 2020-05-28.07:36:23.217>
    actor = 'serhiy.storchaka'
    assignee = 'none'
    closed = True
    closed_date = <Date 2020-05-28.07:36:23.218>
    closer = 'serhiy.storchaka'
    components = ['Interpreter Core']
    creation = <Date 2020-05-27.07:57:47.257>
    creator = 'serhiy.storchaka'
    dependencies = []
    files = []
    hgrepos = []
    issue_num = 40792
    keywords = ['patch']
    message_count = 4.0
    messages = ['370054', '370064', '370071', '370168']
    nosy_count = 3.0
    nosy_names = ['barry', 'mark.dickinson', 'serhiy.storchaka']
    pr_nums = ['20443']
    priority = 'normal'
    resolution = 'fixed'
    stage = 'resolved'
    status = 'closed'
    superseder = None
    type = 'enhancement'
    url = ''
    versions = ['Python 3.10']

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    @serhiy-storchaka serhiy-storchaka commented May 27, 2020

    Currently PyNumber_Index() can return something that's an instance of a strict subclass of int. For example PyNumber_Index(Py_True) returns Py_True. The same for operator.index():

    >>> import operator
    >>> operator.index(True)

    The proposed PR makes it always return an int.

    To avoid possible overhead for creating temporary integer object, added private function _PyNumber_Index() with the past behavior. It can be used for short-living integer objects which for which only its value will be used, but not its methods. For example in the implementation of PyLong_AsLong() and similar functions.

    See also bpo-17576.

    @serhiy-storchaka serhiy-storchaka added 3.10 interpreter-core type-feature labels May 27, 2020
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    @serhiy-storchaka serhiy-storchaka commented May 27, 2020

    This change conflicts with the test added in bpo-26202. We perhaps should revert bpo-26202. This can also affect the user code which depends on range() attributes start, stop and step being instances of the int subclass.

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    @mdickinson mdickinson commented May 27, 2020

    The behaviour change for range sounds reasonable to me.

    Just to make sure I understand the impact of the change:

    • For Python < 3.10, we sometimes convert the range inputs to Python ints, and sometimes don't. For example, a start value of np.int64(5) would be converted, but a value of True would not be.

    • With this change, we'd always convert a non-int to an int, so both np.int64(1) and True would be converted to a 1 of exact type int.

    IMO this is fine; the new behaviour seems more consistent than the old.

    >>> import numpy as np
    >>> start = np.int64(2)
    >>> range(start, 5).start is start
    >>> start = True
    >>> range(start, 5).start is start

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    @serhiy-storchaka serhiy-storchaka commented May 28, 2020

    New changeset 5f4b229 by Serhiy Storchaka in branch 'master':
    bpo-40792: Make the result of PyNumber_Index() always having exact type int. (GH-20443)

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