Python Recursion

In this tutorial, you will learn about the recursive function in Python with the help of examples.

A function that calls itself is known as a recursive function. And the process is known as recursion.

Working of Recursion in Python

def recurse():


The recurse() function calls itself over and over again. The figure below shows how recursion works.

Working of Function Recursion in Python
Working of Function Recursion in Python

Example: Recursion

def greet():

# recursive call greet()
# normal function call greet()



The above program will call itself infinitely. Hence, we must include a stopping condition to stop the recursive call.

Stopping Condition for Recursion

If we do not include a stopping condition to stop the recursive call, the function will keep calling itself infinitely.

We generally use the if...else statement to stop the recursion.

def recurse():
    if condition: 
        # condition to break recursion
        # recursive call

In the above code, the if statement stops the recursive call and the else statement calls the function recursively.

Example: Recursion With Stop Condition

def print_number(number):
    # print number

# stopping condition if number == 0:
print('Stop Printing') else: # recursive call print_number(number - 1) print_number(2)


Stop Printing

In the above example, we have created a recursive function named print_number(). Here, the function calls itself until the number passed to it becomes 0.

Working of the code:

Function call Prints number == 0 ?
print_number(2) 2 False
print_number(2 - 1) 1 False
print_number(1 - 1) 0
Stop Printing
True [function call stops]

Example: Sum of Natural Numbers

def calculate_sum(num):

    # stopping condition
    if num == 1:
        return 1

    # recursive call
    return num + calculate_sum(num - 1)
result = calculate_sum(4)



The calculate_sum(num) function calculates the sum of all integers from num to 1 using recursion.

If num equals 1, it simply returns 1 since that's the base case. Otherwise, it returns num plus the result of a recursive call to calculate_sum(num - 1).

Here, calculate_sum(4) computes the sum of 4, 3, 2, and 1, which is 10.

Working of the Sum of Natural Numbers

Sum of Natural Numbers using Recursion
Sum of Natural Numbers using Recursion

Advantages and Disadvantages of Recursion

The advantages and disadvantages of using recursion in Python are as follows:


  • Recursion makes our code shorter and cleaner.
  • It is required in data structures and algorithms, such as Graph and Tree Traversal.


  • Recursion uses more processor time.
  • Recursive functions are more difficult to debug compared to an equivalent iterative program.
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