On 7/17/2015 7:43 AM, Antoon Pardon wrote:
On 07/17/2015 01:05 PM, Chris Angelico wrote:
def gen():
yield stuff
yield more stuff
for stuff in gen():
bomb with exception
The error didn't happen in the generator, so I wouldn't expect to see
it in the traceback.
Yes something like that. And I wouldn't expect it either but if it
is not present, is it because nobody thought about it or because it
is a bad idea or an idea difficult to implement?
There's still room for the cause of an error to
not be in the traceback; imagine, for instance, a function that
populates a concrete list, and then you iterate over the list. If that
function sticks a None into the list and the subsequent processing is
expecting all strings, that's going to bomb, but then you have to
figure out where the None came from. If the traceback could include
that, it'd be great, but some things aren't possible.
Sure, but in this case, the generator is still active.
No more than any other object sitting around inactive. Calling a
generator function like gen above returns a generator with the generator
function, in a suspended inactive state, attached as an attribute. When
the generator.__next__ function is called, it activates its instance of
the generator function, which suspends itself again after yielding
something. At the point of the exception above, the generator next
function has returned. There could be multiple generators with
suspended generator functions sitting around. For instance:
def f():
for tup in zip(gf0, gf1, gf2, gf3, gf4, gf5):
a = tup[6] # whoops, IndexError
<unreachable code meant to do something>
--
Terry Jan Reedy
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