[Python-Dev] Multiple dicts for string interpolation?

[Skip Montanaro]

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)
    ...
    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.

Skip Montanaro | http://www.mojam.com/
skip@mojam.com | http://www.musi-cal.com/
847-971-7098