How to get list of parameters name from a function in Python?

In this article, we are going to discuss how to get list parameters from a function in Python. The inspect module helps in checking the objects present in the code that we have written. We are going to use two methods i.e. signature() and getargspec() methods from the inspect module to get the list of parameters name of function or method passed as an argument in one of the methods.

Using inspect.signature() method

Below are some programs which depict how to use the signature() method of the inspect module to get the list of parameters name:

Example 1: Getting the parameter list of a method.

Python3

# import required modules
import inspect
import collections

# use signature()
print(inspect.signature(collections.Counter))

Output:

(*args, **kwds)

Example 2: Getting the parameter list of an explicit function.

Python3

# explicit function
def fun(a, b):
    return a**b

# import required modules
import inspect

# use signature()
print(inspect.signature(fun))

Output:

(a, b)

Example 3: Getting the parameter list of an in-built function.

Python3

# import required modules
import inspect

# use signature()
print(inspect.signature(len))

Output:

(obj, /)

Using inspect.getargspec() method

Below are some programs which depict how to use the getargspec() method of the inspect module to get the list of parameters name:

Example 1: Getting the parameter list of a method.

Python3

# import required modules
import inspect
import collections

# use getargspec()
print(inspect.getargspec(collections.Counter))

Output:

ArgSpec(args=[], varargs=’args’, keywords=’kwds’, defaults=None)

Example 2: Getting the parameter list of an explicit function.

Python3

# explicit function
def fun(a, b):
    return a**b

# import required modules
import inspect

# use getargspec()
print(inspect.getargspec(fun))

Output:

ArgSpec(args=[‘a’, ‘b’], varargs=None, keywords=None, defaults=None)

Example 3: Getting the parameter list of an in-built function.

Python3

# import required modules
import inspect

# use getargspec()
print(inspect.getargspec(len))

Output:

ArgSpec(args=[‘obj’], varargs=None, keywords=None, defaults=None)