binsearch.py

def binarySearch(arr, elem):
    return binarySearchHelper(arr, elem, 0, len(arr) - 1)

def binarySearchHelper(arr, elem, low, high):
    if low > high:
        return -1
    else:
        ind = (low + high) // 2
        mid = arr[ind]

        if elem < mid:
            return binarySearchHelper(arr, elem, low, ind - 1)
        elif elem > mid:
            return binarySearchHelper(arr, elem, ind + 1, high)
        else:
            return ind

    return -1

assert binarySearch([0, 1], 0) == 0
assert binarySearch([0, 1], 1) == 1
assert binarySearch([0, 1], -1) == -1
assert binarySearch([0, 1], 2) == -1
assert binarySearch([0], 0) == 0
assert binarySearch([0], 1) == -1
assert binarySearch([0], -1) == -1