Issue 35966: Didn't raise "StopIteration" Error when I use "yield" in the function (original) (raw)

Issue35966

Created on 2019-02-11 13:27 by sheiun, last changed 2022-04-11 14:59 by admin. This issue is now closed.

Messages (3)
msg335215 - (view)	Author: (sheiun)	Date: 2019-02-11 13:27
Python 3.6.7 |Anaconda custom (64-bit)	(default, Oct 28 2018, 19:44:12) [MSC v.1915 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> def generate_loop(): ... for i in range(10): ... print(i) ... # should raise StopIteration when i > 5 ... k = next(j for j in range(5) if j == i) ... print(k) ... yield k ... >>> >>> def generate(): ... # should raise StopIteration ... k = next(j for j in range(5) if j == 6) ... yield k ... >>> >>> print(list(generate_loop())) 0 0 1 1 2 2 3 3 4 4 5 [0, 1, 2, 3, 4] >>> >>> print(list(generate())) [] >>> >>> k = next(j for j in range(5) if j == 6) Traceback (most recent call last): File "", line 1, in StopIteration >>>
msg335216 - (view)	Author: (sheiun)	Date: 2019-02-11 13:31
But it still can catch by using try/except >>> def generate_loop_stopiteration(): ... for i in range(10): ... print(i) ... # should raise StopIteration when i > 5 ... try: ... k = next(j for j in range(5) if j == i) ... except StopIteration: ... print('catch') ... print(k) ... yield k ... >>> print(list(generate_loop_stopiteration())) 0 0 1 1 2 2 3 3 4 4 5 catch 4 6 catch 4 7 catch 4 8 catch 4 9 catch 4 [0, 1, 2, 3, 4, 4, 4, 4, 4, 4] >>>
msg335217 - (view)	Author: SilentGhost (SilentGhost) *	Date: 2019-02-11 13:46
Within a generator function, StopIteration exception is a sign that generator is finished. This is why this exception is caught automatically, and closes generator. This is normal and documented behaviour of generators.