Many method parameters in the datetime module are positional-only in the C implementation but positional-or-keyword in the Python implementation

[AlexWaygood]

BPO	45821
Nosy	@abalkin, @pganssle, @AlexWaygood

^{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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assignee = None
closed_at = None
created_at = <Date 2021-11-16.19:21:08.113>
labels = ['type-bug', '3.9', '3.10', '3.11', 'extension-modules', 'library']
title = 'Many method parameters in the datetime module are positional-only in the C implementation but positional-or-keyword in the Python implementation'
updated_at = <Date 2021-11-21.13:45:40.155>
user = 'https://github.com/AlexWaygood'

bugs.python.org fields:

activity = <Date 2021-11-21.13:45:40.155>
actor = 'AlexWaygood'
assignee = 'none'
closed = False
closed_date = None
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components = ['Extension Modules', 'Library (Lib)']
creation = <Date 2021-11-16.19:21:08.113>
creator = 'AlexWaygood'
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files = []
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issue_num = 45821
keywords = []
message_count = 3.0
messages = ['406423', '406592', '406715']
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priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45821'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[AlexWaygood]

The following methods have parameters that are positional-only in the C implementation of the datetime module, but positional-or-keyword in the pure-Python implementation:

• tzinfo.tzname
• tzinfo.utcoffset
• tzinfo.dst
• tzinfo.fromutc
• date.fromordinal
• date.fromisoformat
• date.__format__
• date.__le__
• date.__lt__
• date.__ge__
• date.__gt__
• date.__add__
• date.__radd__
• date.__sub__
• date.__reduce_ex__
• time.__le__
• time.__lt__
• time.__ge__
• time.__gt__
• time.fromisoformat
• time.__format__
• timedelta.__add__
• timedelta.__radd__
• timedelta.__sub__
• timedelta.__rsub__
• timedelta.__mul__
• timedelta.__rmul__
• timedelta.__floordiv__
• timedelta.__truediv__
• timedelta.__mod__
• timedelta.__divmod__
• timedelta.__le__
• timedelta.__lt__
• timedelta.__ge__
• timedelta.__gt__
• datetime.utcfromtimestamp
• datetime.fromisoformat
• datetime.strptime
• datetime.__le__
• datetime.__lt__
• datetime.__ge__
• datetime.__gt__

These inconsistencies make it extremely difficult to provide an accurate stub for these methods in typeshed.

[AlexWaygood]

It seems to me that there are two ways of resolving this:

(1) Change the Python implementation to match the C implementation (make these parameters positional-only in the Python implementation).

(2) Change the C implementation to match the Python implementation (make these parameters positional-or-keyword in the C implementation).

If the decision is that solution (1) is the way to go, I'd be happy to submit a PR fixing this. If the decision is that solution (2) would be better, however, I'm not confident enough with writing C code to submit a PR.

The C implementation is most widely used, so I think strategy (1) would not have too many backwards-compatibility concerns. Strategy (2) is still probably slightly more backwards-compatible, however.

[AlexWaygood]

Ref to discussion on typeshed: python/typeshed#6343

[StanFromIreland]

I would say (1) is fine (with no backporting) as I doubt there are many use cases for using the Python implementation over the much faster C. I can implement one (or two I guess, using clinic for just a few functions is also not the nicest imo)