[Python-ideas] Revisiting Immutable Mappings

[Zaur Shibzukhov]

вторник, 16 октября 2018 г., 12:29:55 UTC+3 пользователь Steven D'Aprano 
написал:
>
>
> > It seems to me that we would need this restriction to make a reasonably 
> > universal frozendict that is, itself, hashable. 
>
> When people talk about frozendicts being hashable, they mean it in the 
> same sense that tuples are hashable. 
>
>
> For what it is worth, here's an incomplete, quick and dirty proof of 
> concept frozendict, using automatic delegation: 
>
> # Not good enough for production, not tested, buyer beware, etc. 
> class frozendict: 
>     def __new__(cls, *args, **kwargs): 
>         d = dict(*args, **kwargs) 
>         proxy = types.MappingProxyType(d) 
>         instance = super().__new__(cls) 
>         instance.__proxy = proxy 
>         return instance 
>     def __hash__(self): 
>         return hash(tuple(self.items())) 
>     def __getattr__(self, name): 
>         return getattr(self.__proxy, name) 
>     def __getitem__(self, key): 
>         return self.__proxy[key] 
>     def __repr__(self): 
>         return "%s(%r)" % (type(self).__name__, dict(self)) 
>
> For those who need more performant variant (Cython compiled) of frozendict 
frozenmap <https://pypi.org/project/frozenmap/> project can be offer.
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