Variadic Functions - using *args

Python provides a powerful feature called *args, which allows you to create functions that can accept a variable number of arguments. With *args, you can pass any number of arguments to a function, providing flexibility and convenience in your code. Whether you need to work with a fixed number of arguments or handle unpredictable input, *args is a valuable tool in your Python programming arsenal. In this tutorial, we will explore how to define and use variadic functions using *args, and discover practical examples where this feature can simplify your code and make it more adaptable. Let's dive in and master the art of variadic functions in Python!

Using *args in Python :

• We have read about tuple unpacking in the previous tutorial.
• In case of the following tuple unpacking statement -  a, b, *c = 1, 2, 3, 4, 5 
  • 1 is assigned to a
  • 2 is assigned to b
  • [3, 4, 5] is assigned to c
• This same concept is similarly applicable to function arguments as well.
• Suppose we have a function definition :

def my_func(a, b, *c):
 	# function body
 	
 	

• And we make a call to the function using positional arguments like this :
  •   my_func(1, 2, 3, 4, 5) 
• In this case :
  • 1 is assigned to a
  • 2 is assigned to b
  • Tuple (3, 4, 5) is assigned to c
• The only difference in case of function call is that in case of function arguments the args argument is a tuple and not a list.
• Code Sample : 

def my_func(a, b, *c):
    print("a = ", a)
    print("b = ", b)
    print("c = ", c)


my_func(10, 20, 30, 40, 50)

# Output
# a =  10
# b =  20
# c =  (30, 40, 50)

Variadic Parameter - *args :

• The special parameter *args of a function is called a variadic parameter.
• It is a convention to name the variadic parameter as *args but it is not mandatory to name it as args. 
• We can name it as anything e.g. *names, *ids, *price etc.
• Functions that have variadic parameter in their definition are called variadic functions.
• Variadic functions can take variable number of arguments - i.e. zero or more arguments.
• To access the values of the *args argument we use the square bracket notation :
  • args[0]
  • args[1]
  • args[2]
• Also we can use the for loop to iterate over elements of variadic parameter.
• We cannot have any positional argument after variadic parameter.
• Only keyword arguments are allowed after variadic arguments.
• Code Sample :

def my_func(a, b, *args):
    print("Value of a = ", a)
    print("Value of b = ", b)
    print("Value of arg_1 = ", args[0])
    print("Value of arg_2 = ", args[1])
    print("Value of arg_3 = ", args[2])
    print()

    print("Iterating over args")
    # using for loop
    for arg in args:
        print(arg)


my_func(10, 20, 30, 40, 50)

# Output
# Value of a =  10
# Value of b =  20
# Value of arg_1 =  30
# Value of arg_2 =  40
# Value of arg_3 =  50

# Iterating over args
# 30
# 40
# 50