Chris Angelico rosuav at gmail.com
Thu Dec 22 01:08:12 EST 2011

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On Thu, Dec 22, 2011 at 4:45 PM, GZ <zyzhu2000 at gmail.com> wrote:
> def h():
>    if condition=true:
>       #I would like to return an itereator with zero length
>    else:
>       for ...: yield x

Easy. Just 'return' in the conditional.

>>> def h():
	if condition:
		return
	for i in range(4): yield i

>>> condition=False
>>> h()
<generator object h at 0x01913E68>
>>> for i in h(): print(i)

0
1
2
3
>>> condition=True
>>> h()
<generator object h at 0x01079E40>
>>> for i in h(): print(i)

>>>

A generator object is returned since the function contains a 'yield'.
On one of the branches, nothing will ever be yielded and StopIteration
will be raised immediately.

You could probably also raise StopIteration directly, but it's not necessary.

ChrisA

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