bpo-13349: repr object in tuple.index ValueError message

[llllllllll]

The old error of tuple.index(x): x not in tuple seemed very confusing to me. It was also harder to quickly understand what the program was doing wrong. This saves people a second pass through the program under the debugger because they can just see what the invalid value was.

The reason I am explicitly calling repr instead of using %R is that I didn't want to call repr twice if I didn't need to. If people think that is fine the format can just be tuple.index(%R): %R not in tuple instead.

[mention-bot]

@llllllllll, thanks for your PR! By analyzing the history of the files in this pull request, we identified @serhiy-storchaka, @rhettinger and @tiran to be potential reviewers.

[brettcannon]

Please don't do assignment in an if guard as it's hard to notice it's not a comparison.

[brettcannon]

Could you open an issue for this, @llllllllll ? I actually want to discuss the message a bit more.

[llllllllll]

It looks like we just changed the title at the same time, should it include the issue number?

[brettcannon]

@llllllllll yep, race condition. 😬

[DimitrisJim]

I made another PR a couple of months back that address the error message both for tuple.index and in other cases it manifests: #876.

[brettcannon]

I've renumbered this to the superseding issue so we know we have two implementations for a similar idea (assuming the idea even gets approved).

[serhiy-storchaka]

bpo-13349 was closed. The idea was rejected.