Question

What exactly do *args and **kwargs mean?

According to the Python documentation, from what it seems, it passes in a tuple of arguments.

def foo(hello, *args):     print(hello)      for each in args:         print(each)  if __name__ == '__main__':     foo("LOVE", ["lol", "lololol"]) 

This prints out:

LOVE ['lol', 'lololol'] 

How do you effectively use them?

Answer 1

Putting *args and/or **kwargs as the last items in your function definition’s argument list allows that function to accept an arbitrary number of arguments and/or keyword arguments.

For example, if you wanted to write a function that returned the sum of all its arguments, no matter how many you supply, you could write it like this:

def my_sum(*args):     return sum(args) 

It’s probably more commonly used in object-oriented programming, when you’re overriding a function, and want to call the original function with whatever arguments the user passes in.

You don’t actually have to call them args and kwargs, that’s just a convention. It’s the * and ** that do the magic.

The official Python documentation has a more in-depth look.