如何使用元組訪問深度嵌套的字典？

Question

我想擴展the autovivification example在nosklo以前的答案給出允許字典訪問元組。

nosklo的解決方案是這樣的：

---

class AutoVivification(dict): 
    """Implementation of perl's autovivification feature.""" 
    def __getitem__(self, item): 
     try: 
      return dict.__getitem__(self, item) 
     except KeyError: 
      value = self[item] = type(self)() 
      return value 

測試：

a = AutoVivification() 

a[1][2][3] = 4 
a[1][3][3] = 5 
a[1][2]['test'] = 6 

print a 

輸出：

{1: {2: {'test': 6, 3: 4}, 3: {3: 5}}} 

---

我有一個情況，我想設置一個給定任意下標的元組的節點。如果我不知道元組的深度有多少層，那麼我如何設計一種方法來設置合適的節點？

我在想，也許我可以使用類似下面的語法：

mytuple = (1,2,3) 
a[mytuple] = 4 

，但我有拿出一個工作實現麻煩。

---

更新

我有一個基於@ JCash的回答完全工作示例：

class NestedDict(dict): 
    """                  
    Nested dictionary of arbitrary depth with autovivification.    

    Allows data access via extended slice notation.       
    """ 
    def __getitem__(self, keys): 
     # Let's assume *keys* is a list or tuple.        
     if not isinstance(keys, basestring): 
      try: 
       node = self 
       for key in keys: 
        node = dict.__getitem__(node, key) 
       return node 
      except TypeError: 
      # *keys* is not a list or tuple.        
       pass 
     try: 
      return dict.__getitem__(self, keys) 
     except KeyError: 
      raise KeyError(keys) 
    def __setitem__(self, keys, value): 
     # Let's assume *keys* is a list or tuple.        
     if not isinstance(keys, basestring): 
      try: 
       node = self 
       for key in keys[:-1]: 
        try: 
         node = dict.__getitem__(node, key) 
        except KeyError: 
         node[key] = type(self)() 
         node = node[key] 
       return dict.__setitem__(node, keys[-1], value) 
      except TypeError: 
       # *keys* is not a list or tuple.        
       pass 
     dict.__setitem__(self, keys, value) 

可實現輸出一樣使用擴展切片音符上面：

d = NestedDict() 
d[1,2,3] = 4 
d[1,3,3] = 5 
d[1,2,'test'] = 6 

Answer 1

這似乎工作

def __setitem__(self, key, value): 
    if isinstance(key, tuple): 
     node = self 
     for i in key[:-1]: 
      try: 
       node = dict.__getitem__(node, i) 
      except KeyError: 
       node = node[i] = type(self)() 
     return dict.__setitem__(node, i, value) 
    return dict.__setitem__(self, key, value)