01.03.12 11:11, Victor Stinner написав(ла):
You can redefine dict.__setitem__. Ah? It doesn't work here.
dict.__setitem__=lambda key, value: None Traceback (most recent call last): File "<stdin>", line 1, in<module> TypeError: can't set attributes of built-in/extension type 'dict'
Hmm, yes, it's true. It was too presumptuous of me to believe that you have not considered such simple approach. But I will try to suggest another approach. `frozendict` inherits from `dict`, but data is not stored in the parent, but in the internal dictionary. And even if dict.__setitem__ is used, it will have no visible effect. class frozendict(dict): def __init__(self, values={}): self._values = dict(values) def __getitem__(self, key): return self._values[key] def __setitem__(self, key, value): raise TypeError ("expect dict, got frozendict") ...
a = frozendict({1: 2, 3: 4}) a[1] 2 a[5] Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 5, in __getitem__ KeyError: 5 a[5] = 6 Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 7, in __setitem__ TypeError: expect dict, got frozendict dict.__setitem__(a, 5, 6) a[5] Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 5, in __getitem__ KeyError: 5