A difference with "exec" that is not documented

[LRGH]

The following piece of code

    def u():
        exec("a=2")
        print(a)
    u()

prints "2" with python2 but "NameError: name 'a' is not defined" with python3.

The way to have it work with both versions is:

    def u():
        exec("a=2")
        print(locals()['a'])
    u()

[LRGH]

More details in the discussion at http://stackoverflow.com/questions/15086040/behaviour-of-exec-function-in-python-2-and-python-3/