Question

The code

x = 3
def f():
    exec("x = 2")
    print(x)
f()

runs on both Python 2 and Python 3, but prints different results. Is this change documented anywhere? (A pointer to a mailing list discussion would also be fine — I ask this purely out of curiosity.)

Answer 1

That’s because some hackery were removed from Python 3.

The new documentation about the exec() function has some Notes about that but don’t fully explain the situtation.

Python 2, after seeing a exec statement, change every access to vars and functions to LOAD_NAME instead of LOAD_FAST or LOAD_GLOBAL.

Check my other answer about that here.