正如其他人提到的那样，在Python中，执行时o.f(x)实际上是一个两步操作：首先，获取的f属性o，然后使用parameter对其进行调用x。这是因为没有属性而失败的第一步f，并且是调用Python magic方法的那一步__getattr__。
因此，您必须实现__getattr__，并且它返回的内容必须是可调用的。请记住，如果您也尝试获取o.some_data_that_doesnt_exist，__getattr__则将调用相同的名称，并且它不会知道它是“数据”属性还是要寻找的“方法”。
这是返回可调用对象的示例：
class MyRubylikeThing(object):
#...
def __getattr__(self, name):
def _missing(*args, **kwargs):
print "A missing method was called."
print "The object was %r, the method was %r. " % (self, name)
print "It was called with %r and %r as arguments" % (args, kwargs)
return _missing
r = MyRubylikeThing()
r.hello("there", "world", also="bye")
产生：
A missing method was called.
The object was <__main__.MyRubylikeThing object at 0x01FA5940>, the method was 'hello'.
It was called with ('there', 'world') and {'also': 'bye'} as arguments
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