bsearch.py

def bsearch(lst, item):
	bottom, top = 0, len(lst)

	while top - bottom >= 3:
		mid = (top + bottom) // 2

		c = cmp(item, lst[mid])

		if c < 0:
			top = mid
		elif c > 0:
			bottom = mid + 1
		else:
			return True

	if item == lst[bottom]:
		return True

	return top - bottom == 2 and item == lst[bottom + 1]