Remove references to nonexisting __ne__ methods

[serhiy-storchaka]

BPO	41400
Nosy	@warsaw, @rhettinger, @facundobatista, @bitdancer, @serhiy-storchaka, @maxking
PRs	gh-85572: Remove references to nonexisting __ne__ methods #21628

^{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 2020-07-26.10:18:46.387>
labels = ['type-feature', '3.8', '3.9', '3.10', 'docs']
title = 'Remove references to nonexisting __ne__ methods'
updated_at = <Date 2020-08-31.20:33:11.959>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2020-08-31.20:33:11.959>
actor = 'facundobatista'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2020-07-26.10:18:46.387>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 41400
keywords = ['patch']
message_count = 6.0
messages = ['374309', '374331', '374332', '374334', '374341', '376167']
nosy_count = 7.0
nosy_names = ['barry', 'rhettinger', 'facundobatista', 'r.david.murray', 'docs@python', 'serhiy.storchaka', 'maxking']
pr_nums = ['21628']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue41400'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[serhiy-storchaka]

There is the documentation for method __ne__ implementations in classes Set, Mapping, Header, Charset, Binary, but all these implementations are removed now and the default implementation of object.__ne__ is used instead.

[rhettinger]

This will make the docs confusing and create an uncertainty for a user: if they define __eq__, do they, can they, or should they define __ne__.

Also, it feels weird to have lists of five rich comparison methods rather than all six.

Tthe current docs better communicate which methods you need to supply and which methods get given to you for free. Note, there is a dependency. The object.__ne__ method depends on __eq__, so you don't get a useful __ne__ until and __eq__ is defined. The meaning of __ne__ does in fact get changed by these classes.

So, while this doc edit is pedantically correct, it makes the documentation less useable than before. I vote for leaving it as-is.

[rhettinger]

s/pedantic/formally but not helpfully/