On Sat, 04 Apr 2009 13:09:06 +0200, Hendrik van Rooyen wrote:
>>Any object can be hashed if it has a working __hash__ method. There's no
>>reason not to have None hashable -- it costs nothing and allows you to
>>use None as a dict key.
>
> So what happens if I try to pickle the dict and keep it for next time?
You pickle the dict and keep it for next time.
> Will I be able to access whatever I have associated with None?
Yes.
> (directly
> - mydict[None], not in a for loop.) And if I send the pickle to another
> machine and unpickle it, what then?
It just works.
> - is unpickling smart enough to
> construct the dict with the local hash of None?
Yes.
> - Seems to me that if it isn't, and you want to do this, there would
> have to be a fixed, well known value for the hash of None.
Seems to me you have misunderstood the way pickling works.
On one machine:
>>> import pickle
>>> pickle.dump({None: "hello world"}, open("pickled", 'w'))
And then on another:
>>> import pickle
>>> pickle.load(open('pickled'))
{None: 'hello world'}
It just works.
--
Steven
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