codetransformer

If you're interested in this sort of thing, you might also check out https://github.com/llllllllll/codetransformer, which is a general-purpose library for doing these sorts of shenanigans in an almost-sane way. (Disclaimer: I'm one of the library authors). As an example, I've got a PR open right now that lets you do things like: @mutable_locals def f(): out = [] x = 1 out.append(x) locals().update({'x': 2, 'y': 3}) out.append(x) out.append(y) return out assert f() == [1, 2, 3] which works using a combination of ctypes hackery and replacing all LOAD_FAST instructions with appropriately-resolved LOAD_NAME instructions.

This is really cool. The AST transformation stuff here is neat, but relatively well-trodden ground. The more impressive new science here is the lazy_function decorator, which is implemented as a bytecode transformer on the code object that lives inside the decorated function. The author built his own library for the bytecode stuff, which lives here: https://github.com/llllllllll/codetransformer.