CODEWITHSUNDEEP
python
Cerin
Cerin

Reputation: 64719

Preventing exceptions from terminating Python iterator

How do you prevent exceptions from prematurely terminating a Python generator/iterator?

For example, consider the following:

#!/usr/bin/env python

def MyIter():
    yield 1
    yield 2
    yield 3
    raise Exception, 'blarg!'
    yield 4 # this never happens

my_iter = MyIter()
while 1:
    try:
        value = my_iter.next()
        print 'value:',value
    except StopIteration:
        break
    except Exception, e:
        print 'An error occurred: %s' % (e,)

I would expect the output:

value: 1
value: 2
value: 3
An error occurred: blarg!
value: 4

However, after the exception, the iterator terminates and value 4 is never yielded even though I've handled the exception and haven't broken my loop. Why is it behaving this way?

Upvotes: 5

Views: 123

Answers (2)

kindall
kindall

Reputation: 184151

The generator needs to handle the exception within itself; it is terminated if it raises an unhandled exception, just like any other function.

Upvotes: 8

dansalmo
dansalmo

Reputation: 11686

You need to handle whatever exception might occur in the generator:

def MyIter():
    yield 1
    yield 2
    yield 3
    try:
       raise Exception, 'blarg!'
    except Exception:
       pass
    yield 4 # this will happen

Upvotes: 2

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