Pass Optional or Keyword Parameters in Python Functions

To pass optional or keyword parameters from one function to another, collect the arguments using the * and ** specifiers in the function's parameter list But, at first, do know what are *args and **args in Python. Let us understand them ?

Variable-length/ Arbitrary arguments in Python (*args)

Example

When you don't know in advance about the number of arguments to be passed, the arguments are variable-length. Include an asterisk i.e. * before the parameter name while defining the function. Let us see an example:

def demo(*car):
   print("Car 1 = ",car[0])
   print("Car 2 = ",car[1])
   print("Car 3 = ", car[2])
   print("Car 4 = ", car[3])

# call
demo("Tesla", "Audi", "BMW", "Toyota")

Output

('Car 1 = ', 'Tesla')
('Car 2 = ', 'Audi')
('Car 3 = ', 'BMW')
('Car 4 = ', 'Toyota')

Arbitrary Keyword Arguments in Python (**kwargs)

When you don't know in advance about the number of keyword arguments to be passed, the arguments are arbitrary keyword arguments.

Example

Let us see an example ?

def demo(**c):
   print("Car Name: "+c["name"])
   print("Car Model: "+c["model"])

# call
demo(name = "Tesla", model = "2022")

Output

Car Name: Tesla
Car Model: 2022

Pass optional or keyword parameters from one function to another

To pass, collect the arguments using the * and ** in the function's parameter list. Through this, you will get the positional arguments as a tuple and the keyword arguments as a dictionary. Pass these arguments when calling another function by using * and ** ?

def f(a, *args, **kwargs):
   ...
   kwargs['width'] = '14.3c'
   ...
   g(a, *args, **kwargs)