Check if a function is defined within a Python class

Question

What is the correct way in Python 3.7+ to check if a function is defined within a Python class. Example:

class A:

    def fun1(self):
        pass

def fun2():
    pass

I would like to distinguish that A.fun1 was defined within a class and fun2 is not.

You're asking magic(A.fun1) should return True and magic(fun2) should return False, right? — deceze
– deceze ♦, Commented Feb 22, 2021 at 15:41
what is the point of doing this? what problem are you trying to solve? — marcusshep
– marcusshep, Commented Feb 22, 2021 at 15:41
There are inspect.ismethod and inspect.isfunction. ismethod should be called on object. Do these: print(inspect.ismethod(A().fun1), inspect.isfunction(A().fun1)); print(inspect.ismethod(fun2), inspect.isfunction(fun2)). — Arty
– Arty, Commented Feb 22, 2021 at 16:20
@Arty As you pointed out, is method requires instantiating the class which might not be possible or easy or have side effects in certain cases. — Hernan
– Hernan, Commented Feb 22, 2021 at 16:56

a_guest · Accepted Answer · 2021-02-22 16:59:28Z

2

You can use the attribute __qualname__ (defined in PEP 3155) and check whether it contains a . which indicates that this object was defined in a nested scope. Note that this also applies to functions defined inside other functions, so it might give you false positives in that sense.

>>> def test(): ...
... 
>>> test.__qualname__
'test'
>>> class Foo:
...     def test(self): ...
... 
>>> Foo.test.__qualname__
'Foo.test'
>>> def f():
...     def g(): ...
...     return g
... 
>>> f().__qualname__
'f.<locals>.g'

answered Feb 22, 2021 at 16:59

a_guest

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Comments

go2nirvana · Accepted Answer · 2021-02-22 15:36:02Z

-1

Here you go hasattr()

>>> hasattr(A, 'fun1')
>>> True

>>> hasattr(A, 'fun2')
>>> False

answered Feb 22, 2021 at 15:36

go2nirvana

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6 Comments

go2nirvana Over a year ago

And how is my answer not solving that problem?

go2nirvana Over a year ago

Method is a function defined within a class. Determining if class has a specific function is exactly equal to "distinguish that function was defined within a class" - as OP requested.

go2nirvana Over a year ago

Well, i answer what was asked in the question, not playing a "guess what that really means" game.

go2nirvana Over a year ago

In this particular case question was very clear for me, so i see no need to clarify. In fact, if you take a look at answer's at deceze's suggestion: the third answer (and 2nd most voted) is the same as mine. This concludes to me, that questions in fact are similar. And rather than doubting my answer, the appropriate action would be to flag question as duplicate. Anyway, i suggest we move on.

Hernan Over a year ago

@go2nirvana I thought that the last phrase in my question was clarifying this: "I would like to distinguish that A.fun1 was defined within a class and fun2 is not" Which is not the same as saying if a given class defines a function with a given name.

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