Given the Python function:
def a_method(arg1, arg2):
pass
How can I extract the number and names of the arguments. I.e., given that I have a reference to func
, I want the func.[something]
to return ("arg1", "arg2")
.
The usage scenario for this is that I have a decorator, and I wish to use the method arguments in the same order that they appear for the actual function as a key. I.e., how would the decorator look that printed "a,b"
when I call a_method("a", "b")
?
Take a look at the inspect
module - this will do the inspection of the various code object properties for you.
>>> inspect.getfullargspec(a_method)
(['arg1', 'arg2'], None, None, None)
The other results are the name of the *args and **kwargs variables, and the defaults provided. ie.
>>> def foo(a, b, c=4, *arglist, **keywords): pass
>>> inspect.getfullargspec(foo)
(['a', 'b', 'c'], 'arglist', 'keywords', (4,))
Note that some callables may not be introspectable in certain implementations of Python. For Example, in CPython, some built-in functions defined in C provide no metadata about their arguments. As a result, you will get a ValueError
if you use inspect.getfullargspec()
on a built-in function.
Since Python 3.3, you can use inspect.signature()
to see the call signature of a callable object:
>>> inspect.signature(foo)
<Signature (a, b, c=4, *arglist, **keywords)>