Question

What is the best style for a Python method that requires the keyword argument ‘required_arg’:

def test_method(required_arg, *args, **kwargs):


def test_method(*args, **kwargs):
    required_arg = kwargs.pop('required_arg')
    if kwargs:
        raise ValueError('Unexpected keyword arguments: %s' % kwargs)

Or something else? I want to use this for all my methods in the future so I’m kind of looking for the best practices way to deal with required keyword arguments in Python methods.

Answer 1

The first method by far. Why duplicate something the language already provides for you?

Optional arguments in most cases should be known (only use *args and **kwargs when there is no possible way of knowing the arguments). Denote optional arguments by giving them their default value (def bar(foo = 0) or def bar(foo = None)). Watch out for the classic gotcha of def bar(foo = []) which doesn’t do what you expect.