Recursion is a programming method, in which a function calls itself one or more times in its body. Usually, it is returning the return value of this function call. If a function definition follows recursion, we call this function a recursive function.
A recursive function has to terminate to be used in a program. It terminates, if with every recursive call the solution of the problem is becomes smaller and moves towards a base case, where the problem can be solved without further recursion. A recursion can lead to an infinite loop, if the base case is not met in the calls.
Example
The following code returns the sum of first n natural numbers using a recursive python function.
def sum_n(n): if n== 0: return 0 else: return n + sum_n(n-1)
This prints the sum of first 100 natural numbers and first 500 natural numbers
print(sum_n(100)) print(sum_n(500))
Output
C:/Users/TutorialsPoint1/~.py 5050 125250