iterative binary search in python

Today I am going to post the code for binary search. This one is iterative and the next one will be recursive. If you don't know about binary search, please read the wikipedia article first.

Now, here is my Python implementation of binary search algorithm:

def binary_search_iterative(li, left, right, key):
  while True:
    if left > right:
      return -1
    mid = (left + right) / 2
    if li[mid] == key:
      return mid
    if li[mid] > key:
      right = mid - 1
    else:
      left = mid + 1

if __name__ == "__main__":
  li = [1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12]
  left = 0
  right = len(li)
  for key in  [8, 6, 1, 12, 7]:
    index = binary_search_iterative(li, left, right, key)
    print key, index