string interpolation for python

[Yingjie Lan]

> Python already has *3* different built-in string

> formatting/interpolation systems:
...
> I would surmise that your key "implicitly grab variable values from
> the enclosing scope" feature has previously been rejected for being
> too magical.

It grabs because it is an expression in disguise (not a literal). 
If we could make that clear in the way we write it, seems the 
magic level should reduce.to a tolerable (or even likable) level.

Cheers,
Yingjie