Passing format keyword arguments

[hayd]

In python you can do the following:

 >>> "{a}".format(a=1)
'1'

it would be nice to do the same with Formatting.

[ScottPJones]

It's just string interpolation, but restricted to .format. For formatting, it would be good not to use things that are likely to conflict with common characters (like $ or even a bare {).
Swift's method of marking interpolation comes to mind, i.e. \(expr).