Recursive sum

recursive_sum.py

'''N IS REQUIRED PARAMETЕR'''
def recursive_sum1(arr, n):
	n -= 1
	if n < 0:
		return 0
	return arr[n] + recursive_sum1(arr, n)
def recursive_sum2(arr, n):
	# n - value of numbers
	if n == len(arr):
		return 0
	return arr[n] + recursive_sum2(arr, n+1)
def recursive_sum3(a,b):
	if a == 0:
		return b
	return recursive_sum3(a-1, b+1)
a = [1, 2, 3, 4, 5]
print(recursive_sum1(a, len(a)))
print(recursive_sum2(a, 0))
print(recursive_sum3(5,5))