String interpolation using dicts

Everyone knows about about the string interpolation operator, %:

"(%s, %s)" % (1, 2) 

Rarely do you see the often more useful use of interpolation using dicts. Not only is it much more readable once the number of variables you're trying to interpolate grows large, it will also allow you to repeatedly insert the same element if need be:

"(%(key)s, %(key)s)" % {'key': 1}