Documentation for EXTENDED_ARG in dis module is incorrect for >=3.6

[appeltel]

BPO	33104
Nosy	@serhiy-storchaka, @appeltel

^{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 = <Date 2018-03-19.18:09:55.059>
created_at = <Date 2018-03-19.16:21:06.590>
labels = ['3.7', '3.8', 'docs']
title = 'Documentation for EXTENDED_ARG in dis module is incorrect for >=3.6'
updated_at = <Date 2018-03-19.18:09:55.058>
user = 'https://github.com/appeltel'

bugs.python.org fields:

activity = <Date 2018-03-19.18:09:55.058>
actor = 'Eric Appelt'
assignee = 'docs@python'
closed = True
closed_date = <Date 2018-03-19.18:09:55.059>
closer = 'Eric Appelt'
components = ['Documentation']
creation = <Date 2018-03-19.16:21:06.590>
creator = 'Eric Appelt'
dependencies = []
files = []
hgrepos = []
issue_num = 33104
keywords = []
message_count = 3.0
messages = ['314100', '314101', '314107']
nosy_count = 3.0
nosy_names = ['docs@python', 'serhiy.storchaka', 'Eric Appelt']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue33104'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[appeltel]

The documentation for the EXTENDED_ARG instruction in the dis module documentation refers to the way the opcode worked before 3.6: https://docs.python.org/3.6/library/dis.html#opcode-EXTENDED_ARG

As I understand, since moving to 2-byte wordcode in 3.6, each EXTENDED_ARG effectively adds a byte to the argument of the next instruction and they can be chained to allow up to a 32-bit argument. The current documentation refers the 2-byte arguments from the older bytecode used in 3.5 and below.

I'm trying to think of a clear and concise wording for how it works now and will add a PR to fix this issue unless someone gets to it before me.

[serhiy-storchaka]

Isn't this a duplicate of bpo-32625?

[appeltel]

Yes, thanks. I failed to see the duplicate searching for open issues, closing.