datetime types don't work as bases

[tim-one]

BPO	720908
Nosy	@gvanrossum, @tim-one
Files	datetime.fix: Strawman fix

^{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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GitHub fields:

assignee = 'https://github.com/tim-one'
closed_at = <Date 2003-05-17.17:40:01.000>
created_at = <Date 2003-04-14.04:58:53.000>
labels = ['extension-modules']
title = "datetime types don't work as bases"
updated_at = <Date 2003-05-17.17:40:01.000>
user = 'https://github.com/tim-one'

bugs.python.org fields:

activity = <Date 2003-05-17.17:40:01.000>
actor = 'tim.peters'
assignee = 'tim.peters'
closed = True
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2003-04-14.04:58:53.000>
creator = 'tim.peters'
dependencies = []
files = ['838']
hgrepos = []
issue_num = 720908
keywords = []
message_count = 6.0
messages = ['15446', '15447', '15448', '15449', '15450', '15451']
nosy_count = 2.0
nosy_names = ['gvanrossum', 'tim.peters']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue720908'
versions = ['Python 2.3']

[tim-one]

This is probably shallow. Assigned to Guido in case
it's very shallow <wink>:

>>> from datetime import *
>>> class C(date):
...     def whatever(self):
...         return "oops"
>>> c = C(2002, 1, 1)
>>> c.whatever()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'datetime.date' object has no 
attribute 'whatever'
>>> type(c)
<type 'datetime.date'>
>>>

Was reported on c.l.py.

[gvanrossum]

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Well, one shallow thing becomes obvious when you write
c.__class__: it's date, not C! Back to Tim...

[gvanrossum]

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Here's a strawman fix. It makes 'date' a properly
subclassable type, and makes all the other types (except
tzinfo) non-subclassable.

[tim-one]

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I think the date enhancement is fine -- check it in! I'd leave off
removing the basetype flag on the other types, though -- I
expect we'll need to make them subclassable too.

[gvanrossum]

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Done; the rest is up to you!

[tim-one]

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I checked in changes (for 2.3b2) so that time, datetime,
and timedelta are properly subclassable from Python too.
That's all of 'em, so closing this now.