def g():
    yield

print(next(g()))

That prints None, but the Yield expressions documentation doesn't say so. It only talks about "returning the value of expression_list to the generator’s caller", but doesn't say that None gets returned if the optional expression_list isn't given.

Maybe it's stated in the PEPs referenced at the end, but I think one shouldn't have to look that far. It should be right there in the documentation.

Linked PRs

• gh-100201: Document behavior with a bare yield statement #100416
• [3.11] gh-100201: Document behavior with a bare yield statement (GH-100416) #100664
• [3.10] gh-100201: Document behavior with a bare yield statement (GH-100416) #100665