List comp bug?

[Terry Reedy]

<tasjaevan at gmail.com> wrote in message 
news:1144923444.813998.61650 at v46g2000cwv.googlegroups.com...
>   [f() for f in [lambda: t for t in ((1, 2), (3, 4))]]
> is giving me
>   [(3, 4), (3, 4)]
>
> The equivalent using a generator expression:

List comps were originally designed to be equivalent to for loops with 
nested for loops and if blocks.  Generator expressions are know to be 
slightly different and *not* exactly equivalent due to the new local 
namespace.

>    [f() for f in (lambda: t for t in ((1, 2), (3, 4)))]
> is giving me
>    [(1, 2), (3, 4)]

Since, when there is a difference, as above, the genex behavior is more 
often the right or expected behavior (as above), Guido is considering 
making the diference go away in 3.0 by making [stuff] == list((stuff)) (ie, 
listcomp == list(genex)).

Terry Jan Reedy