[New-bugs-announce] [issue43385] heapq fails to sort tuples by datetime correctly

[Michał Kozik]

New submission from Michał Kozik <mike.koikos at gmail.com>:

Tuples (datetime, description) all are sorted by the date except one entry (2021-03-09) which is out of order:

        Expected order:             Actual order:
        2021-03-04 Event E          2021-03-04 Event E
        2021-03-07 Event B          2021-03-07 Event B
        2021-03-08 Event C          2021-03-08 Event C
        2021-03-09 Event A          2021-03-11 Event D
        2021-03-11 Event D          2021-03-09 Event A

In REPL it can be replicated by pasting the following code:

import heapq
from datetime import datetime

event_a = (datetime.strptime('2021-03-09', '%Y-%m-%d'), "Event A")
event_b = (datetime.strptime('2021-03-07', '%Y-%m-%d'), "Event B")
event_c = (datetime.strptime('2021-03-08', '%Y-%m-%d'), "Event C")
event_d = (datetime.strptime('2021-03-11', '%Y-%m-%d'), "Event D")
event_e = (datetime.strptime('2021-03-04', '%Y-%m-%d'), "Event E")

events = []
heapq.heappush(events, event_a)
heapq.heappush(events, event_b)
heapq.heappush(events, event_c)
heapq.heappush(events, event_d)
heapq.heappush(events, event_e)

expected_list = [event_e, event_b, event_c, event_a, event_d]

assert events == expected_list

----------
components: Library (Lib)
files: test_heapq.py
messages: 388012
nosy: mike.koikos
priority: normal
severity: normal
status: open
title: heapq fails to sort tuples by datetime correctly
type: behavior
versions: Python 3.8, Python 3.9
Added file: https://bugs.python.org/file49848/test_heapq.py

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue43385>
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