code: def common_start(strings):
      
  
      def gen_start_strings(string):
          """Generator that yield start sub-strings of length 1, 2, ..."""
  
          for i in xrange(1, len(string) + 1):
              yield string[:i]
  
      # Empty strings list
      if not strings:
          return ""
  
      start_string = ""
  
      # Get sucessively start string of 1st string
      for start_string in gen_start_strings(max(strings)):
          if not all(string.startswith(start_string) for string in strings):
              return start_string[:-1]
  
      return start_string
docs: Returns start sub-string that is common for all given strings
  
      Parameters
      ----------
      strings: List of strings
      \tThese strings are evaluated for their largest common start string