Technique for safely reloading dynamically generated module

[Chris Angelico]

On Fri, Jul 22, 2016 at 2:07 AM, Malcolm Greene <python at bdurham.com> wrote:
> The source file we're generating has one main function (go) with some
> supporting functions and classes as well. Will there be any problems
> referencing additional functions or classes defined in the source that
> gets passed to exec ... as long as references to those functions and
> classes happen within the generated module?
>
> 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?

Functions keep references to their globals, so you should be safe.

> The Python documentation also warns: "Be aware that the return and yield
> statements may not be used outside of function definitions even within
> the context of code passed to the exec() function. The return value is
> None."

Yeah, that's just emphasizing that exec() is looking for module-level
code. Just as you can't put a flush-left "return" statement into a .py
file, you can't use one in exec(). As long as your code builder is
returning a string equivalent to what you'd find in an actual Python
module (that is, exactly what it's already doing, given that you
currently attempt to import it), you'll be fine.

ChrisA