[Python-ideas] Why does += trigger UnboundLocalError?

[Carl M. Johnson]

On Tue, May 31, 2011 at 11:09 PM, Jacob Holm <jh at improva.dk> wrote:

>

> x = 1
> > def f():
> >     # The next statement uses the global x
> >     x += 1
> >     x = 2
> >     # From here, you have a local x
> >
>
>
>  Specifically, the "x = 2" statement (and the lack of a nonlocal
> statement) forces x to be local throughout the function, and the "x +=
> 1" statement then tries to read the local "x" and fails.
>


Yes, Jacob has got exactly what I was proposing. x += 1; x = 2 should
continue to fail, since there would be a = statement in the function body in
that case.

-- Carl
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