Why are types not hashable?

[Chris Liechti]

VanL <vlindberg at verio.net> wrote in news:3CF3E7A4.9010103 at verio.net:
> What prevents this from working:
> 
> >>> import types
> >>> alltypes = [t for t in types.__dict__.keys() if t[:2] != '__']
> >>> typestrings ={}
> >>> for t in alltypes: typestrings[eval('types.' + t): t]

no need for "eval" here... a) there is dict.items() b) there is getattr

> ...
> Traceback (most recent call last):
>    File "<stdin>", line 1, in ?
> TypeError: unhashable type
> 
> 
> Why is <type 'dict'> not hashable?  Surely its not mutable?

it is (py 2.2)...
>>> d = {}
>>> for k,v in types.__dict__.items(): 
... 	if k[-4:] == 'Type':
... 		d[v]=k
... 

or if you want as a one liner in functional style:

d = dict([ (v,k) for k,v in types.__dict__.items() if k[-4:] == 'Type'])

>>> d[int]
'IntType'
>>> d[dict]
'DictType'
>>> dict
<type 'dict'>
>>> 

chris

-- 
Chris <cliechti at gmx.net>