Odd name shadowing in comprehension

[Chris Angelico]

On Sun, Oct 23, 2016 at 2:14 PM, Steve D'Aprano
<steve+python at pearwood.info> wrote:
> There's definitely something strange going on. Compare the what happens when
> the semi-global variable is in the first loop iterable versus the second
> loop iterable. In this first example, y refers to both the global and the
> local, yet strangely there's no error:
>

Right. Disassembly shows that it's something like this:

y = 6
val1 = [(x,y) for x in range(y) for y in range(3)]

def temp(iter):
    ret = []
    for x in iter:
        for y in range(3):
            ret.append((x, y))
    return ret
val2 = temp(iter(range(y)))

That first iterable is evaluated in the outer context, then passed as
a parameter.

ChrisA