find position of a given int in an ordered list

binary_search_algorithm.py

ex_list = [0,1,2,3,4,5,6,7,8,9,10]

def binary_search(lst, num):
    """ find position of a given int in an ordered list """

    beg = 0
    end = len(lst) - 1

    while beg <= end:
        mid = beg + (end - beg + 1) //2
        if lst[mid]  == num:
            return mid
        elif lst[mid] > num:
            end = mid - 1
        else:
            beg = mid + 1

    return None

print(binary_search(ex_list, 4))