Python Interview commonly used algorithms

Search algorithm

Binary search algorithm

 1 def binary_search(alist, item):
 2      binary_index = int(len(alist)/2)
 3      if alist == []:
 4          return None
 5      elif alist[binary_index] > item:
 6          return binary_search(alist[:binary_index], item)
 7      elif alist[binary_index] < item:
 8          result = binary_search(alist[binary_index + 1:], item)
 9          return  None if result is None else result + binary_index + 1
10      elif alist[binary_index] == item:
11          return binary_index