On 6/1/2022 9:59 AM, Chris Angelico wrote:
On Wed, 1 Jun 2022 at 23:55, Serhiy Storchaka <storch...@gmail.com> wrote:
31.05.22 16:21, Chris Angelico пише:
On Tue, 31 May 2022 at 23:00, Aaron L via Python-ideas
<python-ideas@python.org> wrote:
After getting used to writing async functions, I’ve been wanting use a similar
syntax to declare generator functions.
What's the advantage? You can just use normal function syntax to
define them, and it works correctly. Do you need the ability to
declare that it's a generator even without any yields in it?
The advantage is that you cannot accidentally turn a function into a
generator by adding "yield". If the result of the call is ignored (it is
expected to be None), this bug can live a long time. It is a common
issue: test containing yield always passes. Since 3.11 the unittest
module emits a warning if a test method returns not None, but it will
not solve all problems: the test can call helpers, and if they are
generators, the call is virtually no-op. This error can also occur in
non-test code.
That might be nice, but without a massive backward compatibility break
(or another keyword for non-generator functions), it can't happen. Is
there any advantage to being able to declare that it must be a
generator (as opposed to simply returning a generator object)?
Serhiy explains the issues above, and I've been bitten by it.
def fn():
# Do something with side effects, or maybe mutating parameters.
print("foo")
yield 3
fn() # Called for the side effects, but not iterated over. It does not
print "foo".
I agree that the compatibility issues are large and tricky.
Eric
Maybe I just don't work on the right sorts of codebases.
ChrisA
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