how to binary search in python code example

Example 1: iterative binary search python

def binary_search(a, key):
	low = 0
	high = len(a) - 1
	while low < high:
		mid = (low + high) // 2
		if key == a[mid]:
			return True
		elif key < mid:
			high = mid - 1
		else:
			low = mid + 1

	return False

Example 2: binary search in python

def binary_search(item_list,item):
	first = 0
	last = len(item_list)-1
	found = False
	while( first<=last and not found):
		mid = (first + last)//2
		if item_list[mid] == item :
			found = True
		else:
			if item < item_list[mid]:
				last = mid - 1
			else:
				first = mid + 1	
	return found

Example 3: recursive binary search python

def binary_search_recursive(A, key, low, high):
	if low > high:
		return False
	else:
		mid = (low + high) // 2
		if key == A[mid]:
			return True
		elif key < A[mid]:
			return binary_search_recursive(A, key, low, mid - 1)
		else:
			return binary_search_recursive(A, key, mid + 1, high)