On 7/21/2016 12:07 PM, Malcolm Greene wrote:

I assume that one downside to the exec() approach is that there is no
persistent namespace for this code's functions and classes, eg. after
the exec() completes, its namespace disappears and is not available to
code that follows?

Objects only disappear when no references are left. So it is up to you whether you drop the namespace and use a new one for the next exec call or whether you use the same namespace over and over. IDLE's run module does the latter. Simplified, IDLE's Shell simulates the interactive interpreter by sending user input to this code in the run module.

main = fake_main()  # with __name__ = '__main__', __builtins__ = ...
while True:
    try:
        code = user_input()
        exec(code, main)
    except BaseException as e:
        handle_exception(e)

--
Terry Jan Reedy

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