binary_search.py

def binary_search(e, l):
     """Binary search for e in l. Assume l is sorted.
     Return 'True' if e exists, 'False' if not.
     """
     llen = len(l)
     if not llen:
         return False
     mid = llen/2
     if e == l[mid]:
         return True
     else:
         if e == l[mid-1]:
             return True
         if e < l[mid-1]:
             return binary_search(e, l[:mid-1])
         else:
             return binary_search(e, l[mid+1:])