Variables declared in exec'ed code don't become local in Python 3 – documentation?

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.)

score 5 · Accepted Answer · edited May 23 '17 at 12:03

5

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.

edited May 23 '17 at 12:03

Community

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answered Oct 05 '11 at 23:05

JBernardo

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I'm well aware of this -- it doesn't answer my question, though. Thanks anyway :) – Sven Marnach Oct 05 '11 at 23:07
Oh, you're talking about documentation... I never saw it documented but it should be somewhere – JBernardo Oct 05 '11 at 23:10
That's probably the best documentation pointer I'll get, so I accept this answer. – Sven Marnach Oct 05 '11 at 23:31

Ethan Furman · Answer 2 · 2011-11-09T23:46:10.400

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Well, there's this bug report in the bug tracker -- not exactly documentation, though.

Ah, and this one is even better!

Okay, possibly the best one yet.

edited Nov 09 '11 at 23:46

answered Nov 09 '11 at 23:37

Ethan Furman

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Variables declared in exec'ed code don't become local in Python 3 – documentation?

2 Answers2