Dates equality check fails when a date is folded and the other is not #115845
Description
Bug report
Bug description:
In the example I have two dates in the Europe/Rome format, representing 2:00 AM on a day with DST change. One of the dates is folded, the other is not.
from datetime import datetime
from zoneinfo import ZoneInfo
not_folded = datetime(2023, 10, 29, 2, 0, tzinfo=ZoneInfo("Europe/Rome"))
folded = datetime(2023, 10, 29, 2, 0, tzinfo=ZoneInfo("Europe/Rome"), fold=1)
print("Not folded date: ", not_folded.isoformat())
print("The folded date: ", folded.isoformat())
assert folded != not_foldedThe two dates are different, as the isoformat() print shows, and they represent a different moment in time (one is 00:00 UTC, the other one is 01:00 UTC). However, the assert fails:
Not folded date: 2023-10-29T02:00:00+02:00
The folded date: 2023-10-29T02:00:00+01:00
Traceback (most recent call last):
File "/Users/alerinaldi/prova.py", line 10, in <module>
assert folded != not_folded
^^^^^^^^^^^^^^^^^^^^
AssertionError
Of course, this also applies to other situations where dates are compared: I discovered the issue while memoizing the result of a function based on dates using a dict.
from datetime import datetime
from zoneinfo import ZoneInfo
__memoized_dict = {}
def process_date(dt: datetime) -> int:
return int(dt.timestamp())
def memoized_result(dt: datetime) -> int:
if dt in __memoized_dict:
return __memoized_dict[dt]
res = process_date(dt)
__memoized_dict[dt] = res
return res
print(memoized_result(datetime(2023, 10, 29, 2, 0, tzinfo=ZoneInfo("Europe/Rome"))))
print(memoized_result(datetime(2023, 10, 29, 2, 0, tzinfo=ZoneInfo("Europe/Rome"), fold=1)))The second call returns a wrong result.
CPython versions tested on:
3.12
Operating systems tested on:
macOS