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gh-76075: Remove mentions of C's mktime in datetime.timestamp() #92796

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gh-76075: Remove mentions of C's mktime in datetime.timestamp() #92796

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ac936a8
Remove mentions of C's mktime in datetime
slateny May 14, 2022
5df6e33
Add raised error for out of bounds time
slateny May 15, 2022
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10 changes: 2 additions & 8 deletions Doc/library/datetime.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1364,14 +1364,8 @@ Instance methods:

Return POSIX timestamp corresponding to the :class:`.datetime`
instance. The return value is a :class:`float` similar to that
returned by :func:`time.time`.

Naive :class:`.datetime` instances are assumed to represent local
time and this method relies on the platform C :c:func:`mktime`
function to perform the conversion. Since :class:`.datetime`
supports wider range of values than :c:func:`mktime` on many
platforms, this method may raise :exc:`OverflowError` for times far
in the past or far in the future.
returned by :func:`time.time`. Raises :exc:`OSError` for times far in the
past or far in the future.
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@pganssle pganssle May 15, 2022

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I think this is maybe too terse. All the core elements of the documentation are still true, IIRC,the only difference is that timestamp uses different system level calls.

I think we want to replace the specific "calls mktime" with a more generic, "relies on system APIs, which may have a different valid range than datetime."

Also, is it not still possible to get an OverflowError?

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@slateny slateny May 15, 2022 •
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Hmm, it does make sense to give some explanation why OSError might occur, so the generic statement sounds good to me.

As for OverflowError, I'm not sure, but I tried an old date and Adam above tried with a very future date, and both gave OSError. Overly large dates (year=999999) and otherwise invalid times (year=-1, 0) give ValueError and very small years give a negative timestamp, so not too sure how I'd be able to replicate OverflowError

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@AA-Turner AA-Turner May 15, 2022

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On WSL Ubuntu, Python 3.10:

>>> datetime.datetime(9_999, 12, 31).timestamp()
253402214400.0
>>> datetime.datetime(1, 1, 1).timestamp()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: year 0 is out of range
>>> datetime.datetime(1, 1, 2).timestamp()
-62135510325.0

The ValueError for datetime.datetime(1, 1, 1).timestamp() is very odd, as datetime.datetime(1, 1, 1) is legal -- perhaps a bug in the implementation?

A

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@pganssle pganssle May 15, 2022

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The ValueError for datetime.datetime(1, 1, 1).timestamp() is very odd, as datetime.datetime(1, 1, 1) is legal -- perhaps a bug in the implementation?

I think that's this.

Overly large dates (year=999999) and otherwise invalid times (year=-1, 0) give ValueError and very small years give a negative timestamp, so not too sure how I'd be able to replicate OverflowError

Possibly this only occurs on 32-bit platforms? There's a comment here that indicates that might be the issue?

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@slateny slateny May 15, 2022 •
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Actually on second glance, ValueError is for datetime(...) (which has a limit of 9999) and not timestamp, so my mistake there. As for the 32-bit platform, that's a good point as I've only tested on 64-bit

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@slateny slateny May 20, 2022 •
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This commit (need to expand the diff of _datetimemodule.c) seems to have removed mktime along with OverflowError


For aware :class:`.datetime` instances, the return value is computed
as::
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