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 http://stackoverflow.com/a/17705456/603136 for more.

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):
        pass

@Deco
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().

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.

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Closing as "out of date".