Source: 📖 Effective Python item 25

Keyword-only arguments explained

Keyword-only arguments are arguments that can only be passed in by keyword, not by position. To employ keyword-only arguments within a function definition, you can use the * symbol to indicate the end of the positional arguments and the beginning of keyword-only arguments.

def my_function(first, last, *, middle=None):
	if middle:
		print(f'{first} {middle} {last}')
	else:
		print(f'{first} {last})