An iterative and recursive approach to BinarySearch in Python.

Binary Search

def binarySearch(A, i):
    L = 0
    R = len(A)-1
    found = -1
    while L <= R and found == -1:
        M = (L + R)//2
        if A[M] == i:
        	found = M
        else:
            if i < A[M]:
                R = M-1
            else:
                L = M+1
    return found

def binarySearch2(A, i):
	return binarySearchR(A, 0, len(A)-1, i)

def binarySearchR(a, start, end, target):
	middle = (start + end) // 2
	if end < start:
		return -1
	if target == a[middle]:
		return middle
	elif target < a[middle]:
		return binarySearchR(a, start, middle - 1, target)
	else:
		return binarySearchR(a, middle + 1, end, target)

a = [1,1,1,1,1,1,1,2,3,3,3,3,7]
print(binarySearch(a,2))
print(binarySearch2(a,2))