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functools.partial doesn't create bound methods #55913
Description
| BPO | 11704 |
|---|---|
| Nosy | @ncoghlan, @alex |
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 = None
closed_at = <Date 2014-03-30.06:00:26.240>
created_at = <Date 2011-03-28.21:34:11.038>
labels = ['type-feature', 'docs']
title = "functools.partial doesn't create bound methods"
updated_at = <Date 2014-03-30.06:00:26.239>
user = 'https://github.com/alex'bugs.python.org fields:
activity = <Date 2014-03-30.06:00:26.239>
actor = 'ncoghlan'
assignee = 'docs@python'
closed = True
closed_date = <Date 2014-03-30.06:00:26.240>
closer = 'ncoghlan'
components = ['Documentation']
creation = <Date 2011-03-28.21:34:11.038>
creator = 'alex'
dependencies = []
files = []
hgrepos = []
issue_num = 11704
keywords = []
message_count = 4.0
messages = ['132425', '132435', '132438', '215169']
nosy_count = 3.0
nosy_names = ['ncoghlan', 'alex', 'docs@python']
pr_nums = []
priority = 'normal'
resolution = 'wont fix'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue11704'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3']
Activity
alex commentedon Mar 28, 2011
This is related to the discussion we had at the PyCon language summit about C vs Python function binding. If you create a partial instance and put it on a class it doesn't create bound instances. This behavior is a tad surprising in my view. At a minimum it'd be nice if the docs mentioned this.
ncoghlan commentedon Mar 28, 2011
True, this could be documented better - flagging as a docs bug. (It is mentioned at the bottom of http://docs.python.org/library/functools.html#partial-objects, but that could be referenced better from the main documentation of the function higher up in the page)
There's actually more to it than just an oversight though - partial() fills in positional arguments from the left, so using one as a method would require specification of a carefully crafted selection of positional and keyword arguments to ensure the instance was bound and passed in at the right point.
alex commentedon Mar 28, 2011
Indeed I completely missed the section at the bottom. A note in the above section would be a useful addition.
ncoghlan commentedon Mar 30, 2014
With the introduction of functools.partialmethod in 3.4, marking this older docs issue as a "won't fix"