Sequence protocol specifies 2 optional argument for index method:
seq.index(value, [start, [stop]])

array.index(value) needs start and stop arguments too.

+1

Николай Спахиев: Are you only asking for the feature, or are you interested to work on a concrete patch?

I plan to work on a patch.

I decided to work on this, and I would like some review, as this would be my second contribution to cpython. Also, a general question:

As I defined the start and end arguments Py_ssize_t, bigger indexes (more negative or more positive) than what can fit in Py_ssize_t will trigger an overflow error. This should be OK, though, as other functions with index arguments has them as Py_ssize_t - and getarrayitem() itself accepts a Py_ssize_t. Or?

Just take list.index as an example.

Anders Lorentsen: Py_ssize_t is the correct type for an index in the C language. It's not technically possible to create an array object larger than PY_SSIZE_T_MAX items :-)

Serhiy> Just take list.index as an example.

I concur with Serhiy :-)

Writing my tests, I originally looked at Lib/test/seq_tests.py. One test case uses indexes that are (+-)4*sys.maxsize. This does not fit in Py_ssize_t, and so these tests cause my array implementation to raise an overflow exception.

A solution is of course to have the function take general objects instead, and then truncate them down to a number that can fit in Py_ssize_t if it's too negative or positive).

But I concur. It seems more reasonable to stay consistent with the rest of the module, too.

I'll look over the test code to make sure I test for every given scenario (or as many as I can think of), and prepare a PR for this, then :)

This functionality is useful to me. Is this issue still alive? If not, how can I help?

There is a pending PR here : https://github.com/python/cpython/pull/4435 by phaqui. @phaqui do you want to finish your PR ?

As far as I can recall, the patch is generally speaking good to go. A number of discussions arose on various details, however. In any event, I'll take a look at it during the next few days.

I have actually managed to lost my local branch of this fix, though I assume I can just start another one, manually copy over the changes, somehow mark this current PR as cancelled, aborted, or in my option the best: "replaced/superseeded by: [new PR]". In any case, there were discussions that seem to be unresolved, allow me to summarize:

* Document that index() raises ValueError when *value* is not found?
> vstinner: We don't do this, remove this addition.
> serhiy: Other index() methods does this.
---> My patch current does this. Who has final saying here?

* 'start' and 'stop' arguments are not keyword arguments, and also not shown in the signature as '.. start=0 ..' for this very reason (it may make them look as keyword arguments). Also, this lines up with list.index() for consistency. Wishes about changing this for all index()-methods has been expressed, but it seems to be consensus on doing this in unison for all index()-methods at once, in a bigger change... So, what is currently in the PR is good enough for now, or?

* Wording in documentation: Clarify that "the returned index is still relative to the start of the array, not the searched sub sequence" or not?

* Comment in the code about checking the length of the array on each iteration? There were comments about it being "confusing" - and while I agree, the other index()-code for lists, does not comment on this. Again I followed the path of most consistency, but I did receive comments about this. Yes to descriptive comments, or not?

----

Generally speaking: In the end, all I really did was mimic how list.index() is both written and documented, and that's when discussions about issues related to that started occurring, and so I now remember that I halted my PR, waiting for these issues to be resolved.

I found this SO about reclaiming an orphaned pull request:
https://stackoverflow.com/a/53383772

But you may still need to open a new PR for it.

New changeset afd12650580725ac598b2845384771c14c4f952e by Zackery Spytz in branch 'master':
bpo-31956: Add start and stop parameters to array.index() (GH-25059)
https://github.com/python/cpython/commit/afd12650580725ac598b2845384771c14c4f952e