# Mechanics of a recursive function

A function that calls itself is known as a recursive function. A problem can be solved with recursion if it can be broken down into smaller problems that are identical in structure to the overall problem. Find factorial of a number and generate series of numbers using recursion.

## # Python's program to demonstrate use of recursion functions. def main(): # Get a number from user. user_num = int(input("Enter any positive interger: ")) # Get the factorial of the number. fact = factorial(user_num) # Display the output print("The factorial of ", user_num, " is ", fact) # Generate Fibonacci Series upto user input print("\n####################################") print("Fibonacci Series of first", user_num, " numbers.") for fib_num in range(1, user_num): print(fibonacci(fib_num)) # The factorial function uses recursion to calculate # the factorial of a number. def factorial(num): if num == 0: return 1 else: return num * factorial(num - 1) # The fibonacci function returns the nth number # in the Fibonacci series. def fibonacci(num): if num == 0: return 0 elif num == 1: return 1 else: return fibonacci(num - 1) + fibonacci(num - 2) main()

###### Sample output of above program.

C:\Python\programs>pep8 --first recursion.py

C:\Python\programs>python recursion.py

Enter any positive interger: 5

The factorial of 5 is 120

####################################

Fibonacci Series of first 5 numbers.

1

1

2

3

C:\Python\programs>

C:\Python\programs>python recursion.py

Enter any positive interger: 5

The factorial of 5 is 120

####################################

Fibonacci Series of first 5 numbers.

1

1

2

3

C:\Python\programs>

2017-08-06T20:23:53+05:30
2017-08-06T20:23:53+05:30
Amit Arora
Amit Arora
Python Programming Tutorial
Python
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