Python function parameter count [duplicate]

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How to find out the arity of a method in Python

Given a python function, how do I programmatically determine the number of parameter开发者_如何学运维s it takes?

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inspect is your friend in this case

>>> def testFunc(arg1, arg2, arg3, additional='test'):
...     print arg1
... 
>>> import inspect
>>> inspect.getargspec(testFunc)
ArgSpec(args=['arg1', 'arg2', 'arg3', 'additional'], varargs=None, keywords=None, defaults=('test',))
>>> 

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From outside the function, you can use inspect.getargspec(): http://docs.python.org/library/inspect.html#inspect.getargspec

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Take a look at the inspect.getargspec(func) command. That gives you a tuple, the first element of which is a list of the required parameters.