binary_index.py

def binary_index(alist, item):
    first = 0
    last = len(alist)-1
    midpoint = 0

    if(item< alist[first]):
        return 0

    while first<last:
        midpoint = (first + last)//2
        currentElement = alist[midpoint]

        if currentElement < item:
            if alist[midpoint+1] > item:
                return midpoint
            else: first = midpoint +1
            if first == last and alist[last] > item:
                return midpoint
        elif currentElement > item:
            last = midpoint -1
        else:
            if midpoint +1 ==len(alist):
                return midpoint
            while alist[midpoint+1] == item:
                midpoint += 1
                if midpoint + 1 == len(alist):
                    return midpoint
            return midpoint
    return last