[Python-Dev] Polymorphic best practices [was: (Not) delaying the 3.2 release]

[Baptiste Carvello]

R. David Murray a écrit :
> I'm trying one approach in email6:
> Bytes and String subclasses, where the subclasses have an attribute
> named 'literals' derived from a utility module that does this:
> 
>     literals = dict(
>         empty = '',
>         colon = ':',
>         newline = '\n',
>         space = ' ',
>         tab = '\t',
>         fws = ' \t',
>         headersep = ': ',
>         )
> 
>     class _string_literals:
>         pass
>     class _bytes_literals:
>         pass
> 
>     for name, value in literals.items():
>         setattr(_string_literals, name, value)
>         setattr(_bytes_literals, name, bytes(value, 'ASCII'))
>     del literals, name, value
> 
> And the subclasses do:
> 
>     class BytesHeader(BaseHeader):
>         lit = email.utils._bytes_literals
> 
>     class StringHeader(BaseHeader):
>         lit = email.utils._string_literals
> 

I've just written a decorator which applies a similar strategy for insulated 
functions, by passing them an appropriate namespace as an argument. It could be 
useful in cases where only a few functions are polymorphic, not a full class or 
module.

http://code.activestate.com/recipes/577393-decorator-for-writing-polymorphic-functions/

Cheers, B.