[Python-Dev] basenumber redux

[Nick Coghlan]

Alex Martelli wrote:
> I'll be happy to draft a PEP if needed (and just as happy to  
> eventually provide an implementation patch if the PEP's accepted),  
> but wanted to doublecheck on the general issue first!

I haven't really followed the earlier basenumber discussions (aside from the 
sidetrack into the nature of mappings), but why would we want this ability as 
a typecheck and not some form of interface check?

For example, what's wrong with "hasattr(x, __int__)"? That works for all the 
builtin types, and, IMO, anyone defining a direct conversion to an integer for 
a non-numeric type deserves whatever happens to them.

Something like:

   def is_number(x):
       return hasattr(x, '__int__')

   def is_integer(x):
       return x == int(x)

Requiring inheritance from "basenumber" in order to make something behave like 
a real number seems antithetical to both duck-typing and the adaptation PEP.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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