Python Dict.get(k) Returns None Even Though Key Exists

Perhaps my understanding of python's dictionary is not good. But here's the problem. Does it ever happen that a {yolk: shell} pair exists in the dictionary say eggs, but a eggs.ge

Solution 1:

You can reproduce that if you have a custom __hash__ method on mutable objects:

classA:
    def__hash__(self):
        returnhash(self.a)

>>> a1 = A()
>>> a2 = A()
>>> a1.a = 1>>> a2.a = 2>>> d = {a1: 1, a2: 2}
>>> a1.a = 3>>> d.items()
dict_items([(<__main__.A object at 0x7f1762a8b668>, 1), (<__main__.A object at 0x7f17623d76d8>, 2)])
>>> d.get(a1)
None

You can see that d.items() still has access to both A objects, but get can't find it anymore, because the hash value has changed.