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It seems I don't need to edit the Python code, but just the C?

The PEP that explains it was linked on the issue:#102450 (comment)

Basically, (I believe) you need to implement it in both places but only the C version is used by CPython. If you add tests they should run on both implementations so you can ensure you've done things correctly. You should also be able toimport _pydatetime directly to test it manually.

Thanks@wookie184, that makes sense 😄

I do have a query though: the tests that I added in 311f914 are actually passing (./python.exe -m test -v datetimetester.py), despite me not having implemented the feature into the python code yet. My understanding ofPEP399 was that the one file tested both the Python and C implementation, but it seems thatdatetimetester.py actuallyonly tests the C code? Do I have to write the tests for the Python implementation of the library somewhere else?

EDIT: I've since added the Python implementation, but am still not convinced that the Python implementation is getting tested locally (seems to be here on GitHub though).

I've also just noticed that thedatetime and_pydatetime modules give different errors when specifying an invalid day:

>>>fromdatetimeimportdatetimeasc_datetime>>>c_datetime.fromisoformat("2023-01-32T24:00:00")Traceback (mostrecentcalllast):File"<stdin>",line1,in<module>ValueError:dayisoutofrangeformonth

vs

>>>from_pydatetimeimportdatetimeaspy_datetime>>>py_datetime.fromisoformat("2023-01-32T24:00:00")Traceback (mostrecentcalllast):File"<stdin>",line1,in<module>File"/Users/xxx/Documents/personal/cpython/Lib/_pydatetime.py",line1906,infromisoformatreturncls(*(date_components+time_components))^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^File"/Users/xxx/Documents/personal/cpython/Lib/_pydatetime.py",line1717,in__new__year,month,day=_check_date_fields(year,month,day)^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^File"/Users/xxx/Documents/personal/cpython/Lib/_pydatetime.py",line545,in_check_date_fieldsraiseValueError('day must be in 1..%d'%dim,day)ValueError: ('day must be in 1..31',32)

Note how_pydatetime's error message specifies the actual day range for that month. Is this something I should add to the C implementation whilst I'm here? Should just be case of swappingPyErr_SetString() withPyErr_Format() -- although not sure how to replicate it being a tuple.

Note how_pydatetime's error message specifies the actual day range for that month. Is this something I should add to the C implementation whilst I'm here? Should just be case of swappingPyErr_SetString() withPyErr_Format() -- although not sure how to replicate it being a tuple.

We can handle this separately.

@pganssle Also can you rebase against main?

Think I've done this correctly, so hopefully should be good now 🙂