TypeError:\uuuu init\uuuuu（）应返回None，而不是'dict'

Question

正在编写代码Kata，我有以下代码：

class Dictionary():
    def __init__(self):
        return {}                  # my code
        
    def newentry(self, word, definition):
        self[word] = definition    # my code
        return self                # my code

我的测试是：

d = Dictionary()   
d.newentry("Apple", "A fruit")

它失败于：

Traceback (most recent call last):
  File "main.py", line 3, in <module>
    d = Dictionary()
TypeError: __init__() should return None, not 'dict'

有什么建议说明为什么Dictionary类应该返回None而不是dict

Answer 1

一种可能的方法是使用对象变量。正如注释中指出的，__init__是一个初始化器，而不是构造函数

In [7]: class Dictionary():
   ...:     def __init__(self):
   ...:         self.d = {}                 # my code
   ...:
   ...:     def newentry(self, word, definition):
   ...:         self.d[word] = definition    # my code
   ...:         return self
   ...:
   ...:

In [8]: d = Dictionary()
   ...: d.newentry("Apple", "A fruit")
Out[8]: <__main__.Dictionary at 0x11f44b748>