Recursion

Recursion is a technique in which a functions calls itself.

Factorial Example

Factorial is the multiplication of each numbers from 1 to N. For example 4 factorial = 4 * 3 * 2 * 1 = 24.

Let's look at the following example:

def calcFactorial(num): if num == 0: return 1 return num * calcFactorial(num - 1) factorial = calcFactorial(4) print(factorial)

Output:

24

At line 5 the function calls itself but with decremented value as argument.

The recursion should eventually end which is done at line 3.

Stack Overflow Exception

Recursion must have an end condition so an endless self calling is prevented.

If not RecursionError is thrown.

The following example causes such:

def recursiveFunc(): recursiveFunc() recursiveFunc() # Causes exception.