Is there a common way to check in Python if an object is any function type?

I have a function in Python which is iterating over the attributes returned from dir(obj), and I want to check to see if any of the objects contained within is a function, method, built-in function, etc. Normally you could use callable() for this, but I don't want to include classes. The best I've come up with so far is:

isinstance(obj, (types.BuiltinFunctionType, types.FunctionType, types.MethodType))

Is there a more future-proof way to do this check?

Edit: I misspoke before when I said: "Normally you could use callable() for this, but I don't want to disqualify classes." I actually do want to disqualify classes. I want to match only functions, not classes.

Asked by: Ryan888 | Posted: 27-01-2022

Answer 1

The inspect module has exactly what you want:

inspect.isroutine( obj )

FYI, the code is:

def isroutine(object):
    """Return true if the object is any kind of function or method."""
    return (isbuiltin(object)
            or isfunction(object)
            or ismethod(object)
            or ismethoddescriptor(object))

Answered by: Adrian548 | Posted: 28-02-2022

Answer 2

If you want to exclude classes and other random objects that may have a __call__ method, and only check for functions and methods, these three functions in the inspect module

inspect.isfunction(obj)
inspect.isbuiltin(obj)
inspect.ismethod(obj)

should do what you want in a future-proof way.

Answered by: Ryan405 | Posted: 28-02-2022

Answer 3

if hasattr(obj, '__call__'): pass

This also fits in better with Python's "duck typing" philosophy, because you don't really care what it is, so long as you can call it.

It's worth noting that callable() is being removed from Python and is not present in 3.0.

Answered by: David502 | Posted: 28-02-2022

Answer 4

Depending on what you mean by 'class':

callable( obj ) and not inspect.isclass( obj )

or:

callable( obj ) and not isinstance( obj, types.ClassType )

For example, results are different for 'dict':

>>> callable( dict ) and not inspect.isclass( dict )
False
>>> callable( dict ) and not isinstance( dict, types.ClassType )
True

Answered by: Emma813 | Posted: 28-02-2022

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