python中二分查找法的实现方法

def binary_search(alist, item):
  """二分查找 非递归方式"""
  n = len(alist)
  start = 0
  end = n - 1
  while start <= end:
    mid = (start + end) // 2
    if alist[mid] == item:
      return True
    elif item < alist[mid]:
      end = mid - 1
    else:
      start = mid + 1
  return False

if __name__ == '__main__':
  li = [17, 20, 26, 31, 44, 54, 55, 77, 93]
  # print(binary_search(li, 55))
  # print(binary_search(li, 100))

def binary_search_2(alist, item):
  """二分查找 递归方式"""
  n = len(alist)
  if 0 == n:
    return False
  mid = n // 2
  if alist[mid] == item:
    return True
  elif item < alist[mid]:
    return binary_search_2(alist[:mid], item)
  else:
    return binary_search_2(alist[mid + 1:], item)
if __name__ == '__main__':
  li = [17, 20, 26, 31, 44, 54, 55, 77, 93]
  # print(binary_search(li, 55))
  # print(binary_search(li, 100))