This issue tracker has been migrated to GitHub, and is currently read-only.
For more information, see the GitHub FAQs in the Python's Developer Guide.

Title: Add follow_wrapped=True option to help()
Type: enhancement Stage: resolved
Components: Library (Lib) Versions: Python 3.8
Status: closed Resolution: out of date
Dependencies: Superseder:
Assigned To: Nosy List: eamanu, rhettinger, samwyse, taleinat
Priority: normal Keywords: patch

Created on 2017-03-29 15:41 by samwyse, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Pull Requests
URL Status Linked Edit
PR 12915 closed eamanu, 2019-04-22 20:25
PR 22390 closed eamanu, 2020-09-23 20:28
Messages (4)
msg290782 - (view) Author: Samwyse (samwyse) * Date: 2017-03-29 15:41
The help(obj) function uses the type of obj to create its result.  This is less than helpful when requesting help on a wrapped object.  Since 3.5, inspect.signature() and inspect.from_callable() have a follow_wrapped option to get around similar issues.  Adding the option to help() would prevent surprising behavior while still allowing current behavior to be used when needed.  See for more.
msg377503 - (view) Author: Tal Einat (taleinat) * (Python committer) Date: 2020-09-25 19:14
To clarify, to my understanding the issue here is that when using a class as a decorator, and copying the wrapped function's __doc__ to self.__doc__ in __init__, help() will pick up the wrapper class's __doc__ rather than the instance's __doc__.

For example:

class Deco:
    "A decorator."
    def __init__(self, func):
        functools.update_wrapper(self, func)
    def __call__(self, *args, **kwargs):

def double(n):
    "A function."
    return n * 2

help(double) will show "A decorator." rather than "A function." despite the use of functools.update_wrapper().
msg377513 - (view) Author: Emmanuel Arias (eamanu) * Date: 2020-09-26 00:24
Hi @taleinat,

Seems tha the wrapped func already has the __doc__ (in this case) copied.

following your example:

>>> double
<test.Deco object at 0x7fe8d1fd5b20>
>>> double.__doc__
'A function'

so help(double) will print correctly the double doc.
msg377518 - (view) Author: Tal Einat (taleinat) * (Python committer) Date: 2020-09-26 06:54
The issue was not that __doc__ was not copied, but that help() would use the class's __doc__ when called on an instance, even if that instance had its own __doc__.

See the StackOverflow question for another example.

You will not see this issue with the latest master branch, because it has already been resolved by PR GH-19479, as described and discussed in issue40257.

Closing as "out of date".
Date User Action Args
2022-04-11 14:58:44adminsetgithub: 74126
2020-09-26 06:54:20taleinatsetstatus: open -> closed
resolution: out of date
messages: + msg377518

stage: patch review -> resolved
2020-09-26 00:24:49eamanusetmessages: + msg377513
2020-09-25 19:14:22taleinatsetnosy: + taleinat
messages: + msg377503
2020-09-23 20:28:01eamanusetpull_requests: + pull_request21431
2019-04-22 20:25:09eamanusetkeywords: + patch
stage: patch review
pull_requests: + pull_request12841
2019-04-22 17:57:25eamanusetnosy: + eamanu
2019-04-22 07:25:49xtreaksetnosy: + rhettinger

versions: + Python 3.8, - Python 2.7, Python 3.3, Python 3.4, Python 3.5, Python 3.6, Python 3.7
2017-03-29 15:41:05samwysecreate