How to Create Functions with Optional Arguments in Python

John on April 13, 2021

To create an optional argument for a function in Python, give it a default value. When a value for the optional argument is supplied on the function call it will override the default value.

To demonstrate this, let's create a function with a required and optional argument and run it.

def foo(required_arg, optional_arg = ''):
   
   print(required_arg)
   
   if optional_arg:
       print(optional_arg)
       
foo('Hello')

Hello

In the above example, no second argument is supplied yet it runs with no issues. Now we can supply the second argument like this:

def foo(required_arg, optional_arg = ''):
   
   print(required_arg)
   
   if optional_arg:
       print(optional_arg)
       
foo('Hello', 1)

Hello
1

Allow an Infinite Number of Optional Arguments

To allow an infinite number of additional argument to be passed to a function, use the *args parameter. Any additional arguments are put in a tuple.

def foo(required_arg, *args):
   
   print(args)
   print(type(args))    
       
foo('Hello', 1)

(1,)
<class 'tuple'>