issubclass(collections.deque, collections.Sequence) == False

[cool-RR]

BPO	12543
Nosy	@rhettinger, @merwok, @bitdancer, @cool-RR

^{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 = 'https://github.com/rhettinger'
closed_at = <Date 2011-07-12.23:08:34.670>
created_at = <Date 2011-07-12.19:16:10.257>
labels = ['invalid']
title = '`issubclass(collections.deque, collections.Sequence) == False`'
updated_at = <Date 2011-07-19.12:17:51.719>
user = 'https://github.com/cool-RR'

bugs.python.org fields:

activity = <Date 2011-07-19.12:17:51.719>
actor = 'eric.araujo'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2011-07-12.23:08:34.670>
closer = 'rhettinger'
components = []
creation = <Date 2011-07-12.19:16:10.257>
creator = 'cool-RR'
dependencies = []
files = []
hgrepos = []
issue_num = 12543
keywords = []
message_count = 6.0
messages = ['140206', '140214', '140216', '140588', '140642', '140656']
nosy_count = 4.0
nosy_names = ['rhettinger', 'eric.araujo', 'r.david.murray', 'cool-RR']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue12543'
versions = []

[cool-RR]

Is there a good reason that issubclass(collections.deque, collections.Sequence) == False? What's not-sequence-y about deque?

[bitdancer]

Maybe they don't support all Sequence operations? They don't support slicing, certainly, but I can't tell from the collections ABC docs if Sequence is required to support slicing.

[rhettinger]

index() isn't supported.

[merwok]

They don't support slicing, certainly, but I can't tell from the
collections ABC docs if Sequence is required to support slicing.

This looks like a 2.7 docs bug. The table with ABCs mentions __*item__, but not __*slice__, probably because it was written with 3.x in mind (where slices are a type of __*item__). Do you think we need to improve the documentation for slicing, in general and with regards to collections ABCs?

[rhettinger]

Éric, this is not a doc bug. The sequence ABCs do not require slicing support.

[merwok]

The sequence ABCs do not require slicing support.
Understood, but is it said in the docs? David said that he couldn’t find that bit of info, which is why I suggested a doc bug.