Allow callable objects in inspect.getfullargspec

[gsakkis]

BPO	8639
Nosy	@ncoghlan, @benjaminp, @merwok, @voidspace, @durban, @ericsnowcurrently, @1st1
Dependencies	bpo-17481: inspect.getfullargspec should use signature
Files	inspect.patch: Adds support for callable objects in inspect.getfullargspec

^{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 2014-01-29.20:55:18.936>
created_at = <Date 2010-05-06.21:58:28.495>
labels = ['type-feature', 'library']
title = 'Allow callable objects in inspect.getfullargspec'
updated_at = <Date 2014-01-29.20:55:18.933>
user = 'https://bugs.python.org/gsakkis'

bugs.python.org fields:

activity = <Date 2014-01-29.20:55:18.933>
actor = 'yselivanov'
assignee = 'none'
closed = True
closed_date = <Date 2014-01-29.20:55:18.936>
closer = 'yselivanov'
components = ['Library (Lib)']
creation = <Date 2010-05-06.21:58:28.495>
creator = 'gsakkis'
dependencies = ['17481']
files = ['22826']
hgrepos = []
issue_num = 8639
keywords = ['patch']
message_count = 12.0
messages = ['105166', '116518', '140069', '140106', '140111', '140112', '141536', '141539', '141540', '141541', '185929', '209681']
nosy_count = 11.0
nosy_names = ['ncoghlan', 'gsakkis', 'benjamin.peterson', 'eric.araujo', 'michael.foord', 'daniel.urban', 'BreamoreBoy', 'marco.mariani', 'eric.snow', 'maxbublis', 'yselivanov']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue8639'
versions = ['Python 3.3']

[gsakkis]

Not sure if this has been brought before but how about extending getargspec to work with callable instances, i.e. make it equivalent to getargspec(obj.__call__) ?

[marcomariani]

I second this, I depend on this monkeypatch for my turbogears projects, where I use callable objects as error handlers:

    def getargspec(func):
        if getattr(func, '__call__') and not isfunction(func) and not ismethod(func):
            func = func.__call__
        if ismethod(func):
            func = func.im_func
        if not isfunction(func):
            raise TypeError('arg is not a Python function')
        args, varargs, varkw = getargs(func.func_code)
        return args, varargs, varkw, func.func_defaults

but I suppose 2.7 is locked to this change so I propose it for 3.x

[merwok]

Adding to nosy the developers who last touched inspect.

[voidspace]

Doesn't seem like an unreasonable request. Nick / Benjamin, what do you think?

[ncoghlan]

This API has changed around a bit in 3.x, so it is actually inspect.getfullargspec that needs to change (getargspec will inherit the new behaviour though, since it uses getfullargspec internally)

With appropriate docs and tests updates, I don't see a problem with adding the feature, though. Docs should note and tests should ensure that this only goes one level deep - if __call__ isn't a real function either, inspect shouldn't try to follow the descriptor chain down the rabbit hole. Anything else runs the risk of infinite recursion in the face of things like "inspect.getargspec(list)".

[voidspace]

I can produce a patch w/ tests and documentation for you to review Nick.

[maxbublis]

I've ran into the same problem with getfullargspec not supporting callables, so I've written patch with docs and tests, that adds support for any Python callable. As a result of getfullargspec's implementation change, getargspec function also supports callables.

[benjaminp]

I'm -0.5. I think the current patch makes too many assumptions for the caller. For example, someone calling a class may really desire __new__'s signature, not that of __init__. Moreover, conceptually, getargspec() returns the argspec of a directly callable *function* or *method*.

[voidspace]

Right. For a callable object (instance with __call__ method), it's unambiguous which signature you want. For a class it's ambiguous.

[maxbublis]

Agree, support for __new__ or __init__ methods would add some ambiquity, so i've decided to drop __init__ support from patch. Patch has been reuploaded.

[BreamoreBoy]

Would someone please review the patch file as it's out of my league.

[1st1]

This is now fixed in bpo-17481.