python - Binary search implementations -

i'm stuck in implementing 5 different ways of binary chop ( task http://codekata.com/kata/kata02-karate-chop/ ). may give ideas more approaches?
that's have got:
1)

def left_chop(key, arr):     l = 0     r = len(arr)     while l<r:         m = (l+r)/2         if key<=arr[m]:             r = m          else:             l = m+1     return l if key == arr[l] else -1 

2)

def left_chop(key, array, left = 0, right = none):     if right == none:         right = len(array)     if left==right:         return left if key == array[left] else -1     m = (left+right)/2     if key<=array[m]:         return left_chop(key, array, left, m)     else:         return left_chop(key, array, m+1, right) 

3)i know, it's similar first

class find(object):     def __init__(self, key, array):         self.array = array         self.key = key         self.l = 0         self.r = len(array)      def left_chop(self):         while self.l<self.r:             self.step()         return self.l if self.key == self.array[self.l] else -1      def step(self):         m = (self.l+self.r)/2         if self.key<=self.array[m]:             self.r = m         else:             self.l = m+1 

i had tried come in functional programming style, haven't succeeded.

you use generator:

def chopper(array, val):     edges = (0, len(array))     while true:         m = sum(edges)/2         edges = (edges[0], m) if array[m] >= val else (m+1, edges[1])         yield edges  def chopsearch(array, val):     l, r in chopper(array, val):         if array[l] == val:             return l         if l==r:             return -1