Dangerous behavior of list(generator)

[Terry Reedy]

On 12/14/2009 10:21 AM, exarkun at twistedmatrix.com wrote:

> I'm asking about why the behavior of a StopIteration exception being
> handled from the `expression` of a generator expression to mean "stop
> the loop" is accepted by "the devs" as acceptable.

Any unhandled exception within a loop stops the loop,
and the exception is passed to the surrounding code.

> To continue your
> comparison to for loops, it's as if a loop like this:
>
> for a in b:
> c
>
> actually meant this:
>
> for a in b:
> try:
> c
> except StopIteration:
> break

No it does not. If c raises any exception, the loop stops *and* the 
exception is passed up to the surrounding code.

> Note, I know *why* the implementation leads to this behavior.

You do not seem to know what the behavior is.
Read what I wrote last night.

Terry Jan Reedy