[Python-Dev] Sets are mappings?

[Nick Coghlan]

Michael Chermside wrote:
> Nick Coghlan writes:
>> Close enough to on-topic to stay here, I think. However, I tend to think of
>> the taxonomy as a little less flat:
>>
>> basecontainer (anything with __len__)
>>    - set
>>    - basemapping (anything with __getitem__)
>>      - dict
>>      - basesequence (anything which understands x[0:0])
>>          - list
>>          - tuple
>>          - string
>>          - unicode
>>      - basearray (anything which understands x[0:0,])
>>          - Numeric.array/scipy.array

<snip>
> So I have a counter-proposal. Let's NOT create a hierarchy of abstract
> base types for the elementary types of Python. (Even basestring feels
> like a minor wart to me, although for now it seems like we need it.)

Sorry - I meant to indicate that I didn't think the base classes were 
necessary because the relevant checks already existed in a "does it behave 
like one" sense:

   def is_container(x):
     try:
         len(x)
         return True
     except (TypeError, AttributeError):
         return False

   def is_mapping(x):
     return hasattr(x, "__getitem__")

   def is_sequence(x):
     try:
         x[0:0]
         return True
     except LookupError:
         return False

   def is_multiarray(x):
     try:
         x[0:0,]
         return True
     except LookupError:
         return False

I agree it's a definite tangent to the original topic :)

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
---------------------------------------------------------------
             http://www.boredomandlaziness.org