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Difference in equality check between C and Python implementation for datetime module's timedelta and time #81760

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tirkarthi opened this issue Jul 13, 2019 · 6 comments
Closed

Difference in equality check between C and Python implementation for datetime module's timedelta and time #81760

tirkarthi opened this issue Jul 13, 2019 · 6 comments
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3.7 (EOL) end of life 3.8 only security fixes 3.9 only security fixes stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@tirkarthi
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BPO 37579
Nosy @abalkin, @serhiy-storchaka, @pganssle, @miss-islington, @tirkarthi
PRs
  • bpo-37579: Return NotImplemented in Python implementation of __eq__ to match C implementation of datetime for timedelta and time #14726
  • [3.8] bpo-37579: Improve equality behavior for pure Python datetime and time (GH-14726) #14743
  • [3.7] bpo-37579: Improve equality behavior for pure Python datetime and time (GH-14726) #14745
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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 = None
closed_at = <Date 2019-07-14.10:04:38.808>
created_at = <Date 2019-07-13.05:25:41.676>
labels = ['3.7', '3.8', 'type-bug', 'library', '3.9']
title = "Difference in equality check between C and Python implementation for datetime module's timedelta and time"
updated_at = <Date 2019-07-25.21:16:37.867>
user = 'https://github.com/tirkarthi'

    bugs.python.org fields:

    activity = <Date 2019-07-25.21:16:37.867>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2019-07-14.10:04:38.808>
closer = 'p-ganssle'
components = ['Library (Lib)']
creation = <Date 2019-07-13.05:25:41.676>
creator = 'xtreak'
dependencies = []
files = []
hgrepos = []
issue_num = 37579
keywords = ['patch']
message_count = 6.0
messages = ['347773', '347813', '347815', '347821', '347903', '348454']
nosy_count = 5.0
nosy_names = ['belopolsky', 'serhiy.storchaka', 'p-ganssle', 'miss-islington', 'xtreak']
pr_nums = ['14726', '14743', '14745']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue37579'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']
    @tirkarthi
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    As reported by Serhiy on https://bugs.python.org/issue37555#msg347733 there is a difference in __eq__ definition in datetime module's C and Python implementation for timedelta and time. When the other in __eq__ is not of the same type NotImplemented is not returned in Python implementation like C causing equality to behave differently.

    Difference in C implementation and Python implementation for datetime.timedelta.__eq__

    cpython/Modules/_datetimemodule.c

    Line 2152 in c8e7146

    static PyObject * 

    static PyObject *
delta_richcompare(PyObject *self, PyObject *other, int op)
{
    if (PyDelta_Check(other)) {
        int diff = delta_cmp(self, other);
        return diff_to_bool(diff, op);
    }
    else {
        Py_RETURN_NOTIMPLEMENTED;
    }
}

    cpython/Lib/datetime.py

    Line 732 in c8e7146

    def __eq__(self, other): 

    def __eq__(self, other):
    if isinstance(other, timedelta):
        return self._cmp(other) == 0
    else:
        return False

    I will add a PR for this with test.

    @tirkarthi tirkarthi added 3.7 (EOL) end of life 3.8 only security fixes 3.9 only security fixes stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error labels Jul 13, 2019
    @serhiy-storchaka
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    Do you mind to fix also other similar cases if they are? __lt__ and others should have the same property.

    @pganssle
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    New changeset e6b46aa by Paul Ganssle (Xtreak) in branch 'master':
    bpo-37579: Improve equality behavior for pure Python datetime and time (GH-14726)
    e6b46aa

    @miss-islington
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    New changeset 143672c by Miss Islington (bot) in branch '3.8':
    bpo-37579: Improve equality behavior for pure Python datetime and time (GH-14726)
    143672c

    @miss-islington
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    New changeset c6b3106 by Miss Islington (bot) (Xtreak) in branch '3.7':
    [3.7] bpo-37579: Improve equality behavior for pure Python datetime and time (GH-14726) (GH-14745)
    c6b3106

    @serhiy-storchaka
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    See bpo-37685.

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