Python 2 __getattr__ max recursion depth

问题

for example i use this code:

class A(object):
    def __init__(self):
        self.dict1 = {
            'A': 3,
            'B': self.A}
    def __getattr__(self, key):
        if key in self.dict1:
            return self.dict1[key]
a = A()

and when it's runned it throws maximum recursion depth exceeded. Can someone please tell me what am i doing wrong here

回答1:

The reference to self.dict1 inside your __getattr__ method causes __getattr__ to be called again, and so on, hence the infinite recursion. The only safe way to access attributes of self inside __getattr__ is by using references to self.__dict__. Try

def __getattr__(self, key):
    if key in self.__dict__['dict1']:
        return self.__dict__['dict1'][key]

Note also that the absence of an else clause will mean undefined attributes appear to have the value None.

来源：https://stackoverflow.com/questions/34828857/python-2-getattr-max-recursion-depth