问在python中使对象可调用的问题

EN

>>> class a(object):
        def __init__(self):
            self.__call__ = lambda x:x

>>> b = a()

>>> b()

Traceback (most recent call last):
    File "<pyshell#5>", line 1, in <module>
        b()
TypeError: 'a' object is not callable
>>> callable(b)
False

>>> hasattr(b,'__call__')
True
>>>