Recursive factorial in Python

problem

Recursion is a type of repetition. In this post, we calculate factorial using recursion. Factorial is a mathematical term given with the following formula:

n! = n × (n – 1)!

SOLUTION

Due to the recursive nature of the formula, it is easier to implement it using recursion as follows:

factorial.py
				
					def fact(n):
    if n==0:
        return 1
    else:
        return n * fact(n-1)
				
			
running - import in the interpreter

Start your terminal and execute the following:

				
					python3
				
			

Import the factorial.py by specifying only the filetitle without the .py

				
					import factorial
				
			

The factorial.py file needs to be located in the same directory where the interpreter started. If successful, we can now execute the fact function by appending it to the imported name:

				
					factorial.fact(5) #calculate 5!
				
			
output

Looks correct. 5! = 120

conclusion

In this post we saw how to simply write the recursive factorial function. Save it in a file (e.g. factorial.py) and then import it in the Python interpreter and execute the fact function. We could have also extended the program and use the Python main function for testing it out.

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Ellion

Professional IT consultant, writer, programmer enthusiast interested in all sorts of coding.
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