Bug report

Bug description:

def conditional_raise_stop_iteration(i: int):
    if i == 3:
        raise StopIteration
    return i

iterator = map(conditional_raise_stop_iteration, range(5))


print(f"Consuming the iterator: {tuple(iterator)}")
print(f"Consuming the iterator again: {tuple(iterator)}")

Expected behavior

When consuming the iterator again, it should not yield any elements, because it is already exhausted

Actual output

Consuming the iterator: (0, 1, 2)
Consuming the iterator again: (4,)

This is a violation of the document:
https://docs.python.org/3/library/stdtypes.html#iterator.__next__

Once an iterator’s next() method raises StopIteration, it must continue to do so on subsequent calls. Implementations that do not obey this property are deemed broken.

This behavior was discussed at maxfischer2781/asyncstdlib#175, where @maxfischer2781 pointed out that the behavior is a violation of the data model.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-137921: Mark map/accumulate iterators exhausted when the user callback raises… #137936