[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:


New changeset 78ad039bcf1a8c494cbc8e18380cc30665869c3e by Xiang Zhang in branch 
'3.6':
bpo-26915: Test identity first in index() and count() of 
collections.abc.Sequence  (GH-553)
https://github.com/python/cpython/commit/78ad039bcf1a8c494cbc8e18380cc30665869c3e


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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:


New changeset d5d3249e8a37936d32266fa06ac20017307a1f70 by Xiang Zhang in branch 
'master':
bpo-26915: Test identity first in membership operation in index() and count() 
methods of collections.abc.Sequence (GH-503)
https://github.com/python/cpython/commit/d5d3249e8a37936d32266fa06ac20017307a1f70


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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Larry Hastings]

Changes by Larry Hastings :


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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Changes by Xiang Zhang :


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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Changes by Xiang Zhang :


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pull_requests: +454

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Changes by Xiang Zhang :


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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

Ping again.

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

ping

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

Oh, sorry. Make the __len__ signature wrong. Change it.

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Added file: http://bugs.python.org/file43190/issue26915_v4.patch

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

Thanks for review Serhiy and nice thoughts. I make the class inherited directly 
from Sequence. So if the methods in Sequence are OK, the test class is OK.

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Added file: http://bugs.python.org/file43189/issue26915_v3.patch

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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stage: needs patch -> patch review

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Oh, sorry, I was absentminded. In general the patch LGTM. But I think that 
using list subclass for tests is not a good idea. If we make a typo in 
CustomSequence method name (__contain__, inedx, coumt), the test is still 
passed. It would be better to use a class that doesn't have any 
sequence-related methods besides explicitly defined.

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

Serhiy, actually the patch(issue26915_s2.patch) I uploaded early has tried to 
make Sequence.index and Sequence.count consistent. Maybe the issue stage is not 
right.

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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resolution: fixed -> 
stage: patch review -> needs patch

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Raymond Hettinger]

Changes by Raymond Hettinger :


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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

Reopen this since the solution is not complete pointed out by Serhiy and the 
new patch has already been attached(s2).

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status: closed -> open

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

Oops, I forgot about them. I think they should. Raymond mentioned count in 
msg75735. Attach patch to take them in.

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Added file: http://bugs.python.org/file42734/issue26915_s2.patch

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

What about Sequence.index and Sequence.count?

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

In my opinion it's not worth. If there is such an operator in stdlib, I would 
expect more, exposing PyObject_RichCompareBool in Python level, providing a new 
operator like `===`.

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Is it worth to add a function in the operator module that tests arguments for 
identity or equality?

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Raymond Hettinger]

Raymond Hettinger added the comment:

Xiang, hanks for the patch and for the link to Guido's opinion.

Josh, I concur with your sentiments.  In this case the burden is light and is 
likely to prevent future difficulties by keeping the container invariants 
intact.

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resolution:  -> fixed
status: open -> closed

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Roundup Robot]

Roundup Robot added the comment:

New changeset 1c6cf4010df3 by Raymond Hettinger in branch 'default':
Issue 26915:  Add identity checks to the collections ABC __contains__ methods.
https://hg.python.org/cpython/rev/1c6cf4010df3

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

I agree with you josh. Actually that's what I want to know, consistency. But I 
don't mention it in my post, so Guido only gives what to do in this case. In 
this thread, it means does Python code have to keep the invariant mentioned in 
msg75735?

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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assignee:  -> rhettinger
nosy: +serhiy.storchaka

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Josh Rosenberg]

Josh Rosenberg added the comment:

At some point someone really needs to decide if the C layer behavior of 
performing an identity test before full equality checking is something that 
should be emulated at the Python layer or not. The current state seems 
ridiculous, where C containers check identity first simply by using the easier 
RichCompareBool function, while Python containers have to have the 
identity-then-equality check rewritten explicitly, which feels like a DRY 
violation.

Makes it harder for non-CPython implementations too, since they end up either 
not matching CPython behavior, or writing extra code to match the CPython 
quirks.

I have nothing against this patch, but between PyObject_RichCompareBool and the 
various slightly strange behaviors in the argument parsing format codes (which 
leads to silly workarounds like _check_int_field in #20858), I feel like the 
Python code base is getting cluttered with hacks to emulate the hacky C layer.

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Xiang Zhang added the comment:

Add issue number to test method name.

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Added file: http://bugs.python.org/file42688/issue26915_v2.patch

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[SilentGhost]

Changes by SilentGhost :


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nosy: +rhettinger, stutzbach
stage:  -> patch review
type:  -> behavior

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

Changes by Xiang Zhang :


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keywords: +patch
Added file: http://bugs.python.org/file42687/issue26915.patch

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[issue26915] Test identity first in membership operation of ItemsView, ValuesView and Sequence in collections.abc

[Xiang Zhang]

New submission from Xiang Zhang:

__contains__ operation in ItemsView, ValuesView and Sequence in collections.abc 
simply test equality with ==. This introduces inconsistent behaviour with 
built-in containers when encountering objects like NaN, which does not equal to 
itself. I asked something about this on core-mentorship, see 
https://mail.python.org/mailman/private/core-mentorship/2016-April/003543.html.

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components: Library (Lib)
messages: 264688
nosy: xiang.zhang
priority: normal
severity: normal
status: open
title: Test identity first in membership operation of ItemsView, ValuesView and 
Sequence in collections.abc
versions: Python 3.6

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