This is a follow-up of Wikipedia Trie pseudocode in Python

This is a follow-up of Wikipedia Trie pseudocode in Python

c 
 o 
 o 
 k 
 i 
 n 
 g 
 # 
 u 
 g 
 h 
 t 
 # 
 n 
 t 
 # 
b 
 a 
 n 
 a 
 n 
 a 
 # 
 n 
 i 
 n 
 g 
 # 
 e 
 d 
 # 
 d 
 # 

c 
 o 
 o 
 k 
 i 
 n 
 g 
 # 
 u 
 g 
 h 
 t 
 # 
 n 
 t 
 # 
b 
 a 
 n 
 a 
 n 
 a 
 # 
 n 
 i 
 n 
 g 
 # 
 e 
 d 
 # 
 d 
 #

b 
 a 
 d 
 n 
 a 
 n 
 a 
 n e 
 d 
 i 
 n 
 g 
c 
 o 
 o 
 k 
 i 
 n 
 g 
 u n 
 t 
 g 
 h 
 t 

import collections
import doctest
class Trie:
 """
 Implements a Trie (also known as 'digital tree', 'radix tree' or 'prefix tree').
 Where common starting letters of many words are stored just once.
 """
 def __init__(self):
 self.child = collections.defaultdict(Trie)
 
 def insert(self, string):
 """
 Add a given string to the trie, modifying it **in place**.
 
 >>> t = Trie()
 >>> t.insert('hello')
 >>> t.insert('hi')
 >>> list(sorted(t.child.keys()))
 ['h']
 >>> first_node = t.child['h']
 >>> list(sorted(first_node.child.keys()))
 ['e', 'i']
 As you can see, the same `h` was written only once,
 and it is connected with both `i` and `e`.
 """
 node = self
 for char in string:
 node = node.child[char]
 
 def __contains__(self, word):
 """
 >>> t = Trie()
 >>> t.insert('example')
 >>> 'example' in t
 True
 >>> 'exemplum' in t
 False
 >>> t.insert('bana')
 >>> 'banana' in t
 False
 """
 trie = self
 for char in word:
 if char in trie.child:
 trie = trie.child[char]
 else:
 return False
 return True
 
 def __str__(self, depth = 0):
 """
 Shows a nicely formatted and indented Trie.
 
 Cannot be tested as equivalent representations
 are arbitrarly chosen from (`dict`s are not ordered).
 """
 s = []
 for i in self.child:
 s.append( '{}{} {}'.format(
 ' ' * depth, i, '\n' + self.child[i].__str__(depth + 1)))
 return ''.join(s)
 
if __name__ == '__main__':
 doctest.testmod()
 trie = Trie()
 for word in ('banning', 'banned', 'banana', 'bad', 'cooking', 'cought', 'count'):
 trie.insert(word)
 print(trie)

c 
 o 
 o 
  k 
  i 
 n 
  g 
 # 
 u 
 g h 
 t 
 # 
 n 
 t  # 
b 
 a 
 n 
 a 
 n 
  a 
 # 
  n 
 i 
 n 
 g 
  # 
 e 
  d 
  # 
 d  # 

# signals the end of a word.

import collections
import doctest
class Trie:
 """
 Implements a Trie (also known as 'digital tree', 'radix tree' or 'prefix tree').
 Where common starting letters of many words are stored just once.
 """
 def __init__(self):
 self.child = collections.defaultdict(Trie)
 
 def insert(self, string):
 """
 Add a given string to the trie, modifying it **in place**.
 
 >>> t = Trie()
 >>> t.insert('hello')
 >>> t.insert('hi')
 >>> list(sorted(t.child.keys()))
 ['h']
 >>> first_node = t.child['h']
 >>> list(sorted(first_node.child.keys()))
 ['e', 'i']
 As you can see, the same `h` was written only once,
 and it is connected with both `i` and `e`.
 """
 node = self
 for char in string:
 node = node.child[char]
 node = node.child[None]
 def __contains__(self, word):
 """
 >>> t = Trie()
 >>> t.insert('example')
 >>> 'example' in t
 True
 >>> 'exemplum' in t
 False
 >>> t.insert('bana')
 >>> 'banana' in t
 False
 >>> t.insert('banning')
  >>> t.insert('banned')
 """
 trie = self
 for char in word:
 if char in trie.child:
 trie = trie.child[char]
 else:
 return False
 return True
 
 def __str__(self, depth = 0):
 """
 Shows a nicely formatted and indented Trie.
 
 Cannot be tested as equivalent representations
 are arbitrarly chosen from (`dict`s are not ordered).
 """
 s = []
 for i in self.child:
 s.append( '{}{} {}'.format(
 ' ' * depth, i or '#', '\n' + self.child[i].__str__(depth + 1)))
 return ''.join(s)
 
if __name__ == '__main__':
 doctest.testmod()
 trie = Trie()
 for word in ('banning', 'banned', 'banana', 'bad', 'cooking', 'cought', 'count'):
 trie.insert(word)
 print(trie)