[Python-Dev] Multiple dicts for string interpolation?

[Jim Fulton]

Skip Montanaro wrote:
> 
> Every once in awhile I want to perform string interpolation using more than
> one dictionary.  One way is to build a dictionary that's a union of multiple
> dictionaries:
> 
>     dict = {}
>     dict.update(d1)
>     dict.update(d2)
>     ...
>     s = format % dict
> 
> Another way is the MultiDict approach that Digital Creations (used to?) use
> in their DocumentTemplate module (I can't remember the exact usage any
> more):
> 
>     dict = MultiDict()
>     dict.append(d1)
>     dict.append(d2)

Actually, push (and pop). The namspaces are managed as a stack.

>     ...
>     s = format % dict
> 
> A MultiDict object maintains a list of the dicts it's been fed and searches
> them in order when __getitem__ is called.
> 
> I'd like to propose a third alternative.  How about if the string
> interpolation function accepted a tuple of dictionaries directly:
> 
>     s = format % (d1, d2)
> 
> It would only be used when named interpolation was expected.  I don't think
> there would be any conflict with current % operator semantics.

Yes. In the current semantics, you output the two dictionaries.

Try: 

  '%s %s' % ({'hello':'skip'},{})

Jim

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