python - 一个类需要实现什么才能用作参数元组？

Question

我希望能够做类似下面的事情

class C(object):
     # I store a series of values in some way
     # what do I need to implement to act like an array of arguments


c=C()
result=f(*c)

在此用法中，*“operator”在实例上调用了什么？

Answer 1

有两种方法可以控制 * 操作符的行为:

1. 重载 __iter__ special method :

   >>> class C(object):
   ...     def __init__(self, lst):
   ...         self.lst = lst
   ...     def __iter__(self):
   ...         return iter(self.lst)
   ...
   >>> def f(a, b, c):
   ...     print "Arguments: ", a, b, c
   ...
   >>> c = C([1, 2, 3])
   >>> f(*c)
   Arguments:  1 2 3
   >>>
   

2. 重载 __getitem__ special method :

   >>> class C(object):
   ...     def __init__(self, lst):
   ...         self.lst = lst
   ...     def __getitem__(self, key):
   ...         return self.lst[key]
   ...
   >>> def f(a, b, c):
   ...     print "Arguments: ", a, b, c
   ...
   >>> c = C([1, 2, 3])
   >>> f(*c)
   Arguments:  1 2 3
   >>>