Enhance Object/structseq.c to match namedtuple and tuple api

[tiran]

BPO	1820
Nosy	@malemburg, @birkenfeld, @rhettinger, @terryjreedy, @amauryfa, @abalkin, @salty-horse, @jackdied, @ericvsmith, @giampaolo, @tiran, @benjaminp, @merwok, @ericsnowcurrently
Files	structseq_subclasses_tuple.diff: patch which makes structseq a subclass of tuple structseq.diff: Tuple subclass patch with tests. structseq_1.patch: Add _fields, _replace, _asdict and eval(repr(s)) structseq_fields.patch: Add only _fields structseq_repr_issue.diff: repr() issue with unnamed fields

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

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2008-01-14.04:20:27.181>
labels = ['extension-modules', 'easy', 'type-feature', '3.9']
title = 'Enhance Object/structseq.c to match namedtuple and tuple api'
updated_at = <Date 2020-01-15.21:54:55.660>
user = 'https://github.com/tiran'

bugs.python.org fields:

activity = <Date 2020-01-15.21:54:55.660>
actor = 'vstinner'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2008-01-14.04:20:27.181>
creator = 'christian.heimes'
dependencies = []
files = ['9159', '9170', '32525', '35367', '35802']
hgrepos = []
issue_num = 1820
keywords = ['patch', 'easy']
message_count = 42.0
messages = ['59888', '59891', '59949', '59955', '59956', '59957', '62830', '62831', '81627', '85097', '90461', '90472', '90506', '90953', '104559', '104562', '109503', '113451', '113453', '113456', '133351', '133355', '133364', '133367', '191872', '192849', '198291', '202330', '202333', '207994', '217301', '217337', '217365', '217468', '217512', '219037', '219150', '219297', '219381', '220315', '220316', '221902']
nosy_count = 21.0
nosy_names = ['lemburg', 'georg.brandl', 'rhettinger', 'terry.reedy', 'amaury.forgeotdarc', 'gjb1002', 'belopolsky', 'salty-horse', 'jackdied', 'eric.smith', 'giampaolo.rodola', 'christian.heimes', 'benjamin.peterson', 'adlaiff6', 'eric.araujo', 'Arfrever', 'santoso.wijaya', 'eric.snow', 'sunfinite', 'abarnert', 'Philip Dye']
pr_nums = []
priority = 'low'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue1820'
versions = ['Python 3.9']

Linked PRs

• GH-46145: make PyStructSequence compatible with namedtuple #108648

[tiran]

Raymond Hettinger wrote:

Here's a couple more if you want to proceed down that path:

1. Have structseq subclass from PyTupleObject so that isinstance(s,
   tuple) returns True. This makes the object usable whenever
   tuples are needed.

2. Add _fields, _asdict, and _replace to match the API in
   collections.namedtuple(). The _fields tuple should only include the
   visible positional fields while _asdict() and _replace() should include
   all of the fields whether visible or accessible only by
   attribute access.

3. Change the constructor to accept keyword args so that eval(repr(s))
   == s works.

NOTE:
I've marked the task as easy but it's not a task for a total newbie.
It's a feasible yet challenging task for somebody who likes to get into
CPython core programming. Basic C knowledge is required!

[adlaiff6]

Here is a patch for #1. I ran make test, and nothing was broken that
seemed to be my fault, so I assume it's okay.

Yes, it's small, it's my first one here. I'll get to the other two
tomorrow.

[rhettinger]

Thanks for the patch. I removed the whitespace changes and added some
tests to make sure structseq now works with the % formatting operator
and isinstance(t,tuple).

Am getting a sporadic segfault in test_zipimport when running "make
test", so holding-off on applying:

test_zipimport
~/py26/Lib/test/test_zipimport.py:91: ImportWarning: Not importing
directory '/home/rhettinger/py26/Modules/zlib': missing __init__.py
["__dummy__"])
make: *** [test] Segmentation fault

[adlaiff6]

I just svn upped (it updated zipimport) and applied your patch, and
'./python Lib/test/regrtest.py test_zipimport.py' says it's okay, so I
would go ahead and commit it.

[rhettinger]

Run, "make test" a few times to make sure it doesn't bomb.

The problem may be due to needing a deferred_type instead of assigning
&PyTupleObject directly. Will look it more later.

[rhettinger]

It worked fine on a fresh check-out. Committed in revision 59967.

[birkenfeld]

Is there something else to be done for this to be closed?

[rhettinger]

All three items are still open. The second one is the easiest.

[rhettinger]

See also bpo-2308

[rhettinger]

Jack, do you have any interest in putting this one over the goal line?