Lispy languages like to use this construct for all kinds of purposes. See the appendix at the end of http://paulgraham.com/icad.html http://paulgraham.com/icad.

Lispy languages like to use this construct for all kinds of purposes. See the appendix at the end of http://paulgraham.com/icad.html http://paulgraham.com/icad.html for examples. You can do this in Python too, but it requires a bit more work. Python is asymmetrical here; you can see a variable in an enclosing scope, and if it's a mutable object you can change it, but you cannot reassign the name.