Python simple binary search

binary_search.py

def binary_search(input_array, value):
    low = 0
    high = len(input_array) -1
    while low <= high:
        middle_idx = (low + high)/2
        middle = input_array[middle_idx]
        if value < middle:
            high = middle_idx - 1
        elif value > middle:
            low = middle_idx + 1
        else:
            return middle_idx
    return -1