How to catch coroutine StopIteration exception?

Question

I use python2.7.

def printtext():
    try:
        line = yield
        print line
    except StopIteration:
        pass

if __name__ == '__main__':
    p = printtext()
    p.send(None)
    p.send('Hello, World')

I try to catch StopIteration exception but it is still raised without being caught.

Could you please give me some hint why the StopIteration exception escaped in this case?

Answer 1

You're misunderstanding when StopIteration is raised. StopIteration is raised when a generator function exits, not during a yield expression. As such, the only way to catch this is to do it outside the function...

def printtext():
    line = yield
    print line

if __name__ == '__main__':
    p = printtext()
    p.send(None)
    try:
        p.send('Hello, World')
    except StopIteration:
        pass