Is there a way to check a function's signature in Python?

You can use:

import inspect
len(inspect.getargspec(foo_func)[0])

This won't acknowledge variable-length parameters, like:

def foo(a, b, *args, **kwargs):
    pass

You should use inspect.getargspec.

inspect.getargspec is deprecated in Python 3. Consider something like:

import inspect
len(inspect.signature(foo_func).parameters)

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