Any built-in ishashable method ?

[Jean-Michel Pichavant]

Hello people,

Is there any built-in way to know if an object is a valid dictionary key ? From what I know, the object must be hashable, and from the python doc, an object is hashable if it has the __hash__ and (__cmp__ or __eq__) methods.

http://docs.python.org/2/glossary.html#term-hashable

I found this on the net, but considering the above definition, does it really check the cmp/eq existence ?

def ishashable(x):
    try:
        hash(x)
    except TypeError:
        return False
    else:
        return True

I was trying to know if any custom class can be used as a dict key. It looks like you can. Yet I'm a little bit concerned, because last time I used invalid objects as keys, I got a bug that was really difficult to spot.

Regards,

JM


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