Binary Search using Python

 1 def binary_search(needle, haystack):
 2     imin, imax = 0, len(haystack)
 3     while True:
 4         if imin >= imax:
 5             return -1
 6         midpoint = (imin + imax) // 2
 7         if haystack[midpoint] > needle:
 8             imax = midpoint
 9         elif haystack[midpoint] < needle:
10             imin = midpoint+1
11         else:
12             return midpoint