I wrote a thing for doing string interpolation in Python, like "Hello, {foo}!".format(foo="World"), except that fields are taken from the calling scope rather than being explicitly supplied.

Using it is simple:

>>> from interpolate import i
>>> foo = "bar"
>>> bar = 123
>>> print i % "{foo} {bar:09}"
bar 000000123

The "field name" can be an expression:

>>> foo = 5
>>> bar = 8
>>> i % "{foo + bar}"
'13'

Compiler flags are preserved:

>>> foo = 8
>>> bar = 5
>>> i % "{foo/bar}"
'1'
>>> from __future__ import division
>>> i % "{foo/bar}"
'1.6'

It works for functions too (integer keys like {0} are positional arguments):

>>> def f(a, b):
...     print i % "{a}, {1}!"
... 
>>> f("Hello", "world")
Hello, world!

And it sort of works for closed-over variables. This works:

>>> def foo(bar):
...     def fubar():
...         frobnicate(bar)
...         print i % "frobnicated {bar}"
...     return fubar
... 
>>> foo(12345)()
frobnicated 12345

but it only works as long as the variable name bar appears somewhere in fubar, or Python won't know to close over bar. Apart from that (do you often interpolate closed-over variables you don't otherwise use?) it's pretty much like real string interpolation.

It's here if you want to download it. pip install interpolate