Add start and stop parameters to the array.index()

[nikispahiev]

BPO	31956
Nosy	@rhettinger, @serhiy-storchaka, @Phaqui, @csabella, @corona10, @ZackerySpytz, @nanjekyejoannah, @kamilturek
PRs	bpo-31956: Add start and stop parameters to array.index() #4435 bpo-31956: Add start and stop parameters to array.index() #25059
Files	WIP-issue-31956

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2021-04-09.01:26:32.579>
created_at = <Date 2017-11-06.11:13:47.630>
labels = ['extension-modules', 'type-feature', '3.10']
title = 'Add start and stop parameters to the array.index()'
updated_at = <Date 2021-04-09.01:26:32.577>
user = 'https://bugs.python.org/nikispahiev'

bugs.python.org fields:

activity = <Date 2021-04-09.01:26:32.577>
actor = 'corona10'
assignee = 'none'
closed = True
closed_date = <Date 2021-04-09.01:26:32.579>
closer = 'corona10'
components = ['Extension Modules']
creation = <Date 2017-11-06.11:13:47.630>
creator = 'niki.spahiev'
dependencies = []
files = ['47261']
hgrepos = []
issue_num = 31956
keywords = ['patch']
message_count = 14.0
messages = ['305629', '305643', '305650', '305758', '306133', '306143', '306150', '306178', '330746', '350405', '350619', '352499', '369732', '390070']
nosy_count = 10.0
nosy_names = ['rhettinger', 'serhiy.storchaka', 'Phaqui', 'cheryl.sabella', 'corona10', 'ZackerySpytz', 'niki.spahiev', 'nanjekyejoannah', 'Ryan G.', 'kamilturek']
pr_nums = ['4435', '25059']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue31956'
versions = ['Python 3.10']

[nikispahiev]

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

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

[rhettinger]

+1

[vstinner]

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

[nikispahiev]

I plan to work on a patch.

[phaqui]

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?

[serhiy-storchaka]

Just take list.index as an example.

[vstinner]

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 :-)

[phaqui]

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 :)