[New-bugs-announce] [issue35756] Using `return value` in a generator function skips the returned value on for-loop iteration

[Bryan Koch]

New submission from Bryan Koch <bbkoch94 at gmail.com>:

Using the new "`return value` is semantically equivalent to `raise StopIteration(value)`" syntax created in PEP-380 (https://legacy.python.org/dev/peps/pep-0380/#formal-semantics) causes the returned value to be skipped by standard methods of iteration.

The PEP reads as if returning a value via StopIteration was meant to signal that the generator was finished and that StopIteration.value was the final value.  If StopIteration.value is meant to represent the final value, then the built-in for-loop should not skip it and the current implementation in 3.3, 3.4, 3.5, and 3.6 should be considered an oversight of the PEP and a bug (I don't have a version of 3.7 or 3.8 to test newer versions).

Reproduction code is attached with comments/annotations.

----------
files: ex1.py
messages: 333802
nosy: Bryan Koch
priority: normal
severity: normal
status: open
title: Using `return value` in a generator function skips the returned value on for-loop iteration
type: behavior
versions: Python 3.4, Python 3.5, Python 3.6
Added file: https://bugs.python.org/file48062/ex1.py

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