Format mini-language integer definition is incorrect

[ncoghlan]

BPO	32720
Nosy	@ncoghlan, @serhiy-storchaka, @nathankerr96, @Mariatta, @miss-islington
PRs	bpo-32720: Fixed incorrect definition in format mini-language doc #5482 [3.7] bpo-32720: Fixed the definition for width and precision in format mini-language doc (GH-5482) #5524 [3.6] bpo-32720: Fixed the definition for width and precision in format mini-language doc (GH-5482) #5525 bpo-32720: Fixed the replacement field grammar documentation. #5544 [3.7] bpo-32720: Fixed the replacement field grammar documentation. (GH-5544) #5546 [3.6] bpo-32720: Fixed the replacement field grammar documentation. (GH-5544) #5547

^{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 2018-02-12.08:09:29.451>
created_at = <Date 2018-01-30.04:45:29.335>
labels = ['easy', '3.8', 'type-bug', '3.7', 'docs']
title = 'Format mini-language integer definition is incorrect'
updated_at = <Date 2018-02-12.08:09:29.449>
user = 'https://github.com/ncoghlan'

bugs.python.org fields:

activity = <Date 2018-02-12.08:09:29.449>
actor = 'Mariatta'
assignee = 'docs@python'
closed = True
closed_date = <Date 2018-02-12.08:09:29.451>
closer = 'Mariatta'
components = ['Documentation']
creation = <Date 2018-01-30.04:45:29.335>
creator = 'ncoghlan'
dependencies = []
files = []
hgrepos = []
issue_num = 32720
keywords = ['patch', 'easy']
message_count = 11.0
messages = ['311229', '311471', '311586', '311587', '311588', '311589', '311636', '311657', '311758', '312032', '312033']
nosy_count = 6.0
nosy_names = ['ncoghlan', 'docs@python', 'serhiy.storchaka', 'nkerr', 'Mariatta', 'miss-islington']
pr_nums = ['5482', '5524', '5525', '5544', '5546', '5547']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue32720'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[ncoghlan]

I just noticed that https://docs.python.org/3/library/string.html#formatspec links to the "integer" definition in the main Python grammar for the permitted format of numeric fields.

This isn't accurate:

>>> format(10e4, ",.2f")
'100,000.00'
>>> format(10e4, ",.0x2f")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Invalid format specifier
>>> format(10e4, ",.2_2f")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Invalid format specifier

Instead, the width and precision subfields should be defined as "digit+"

[nathankerr96]

Just submitted a PR for this issue, however I only signed the CLA an hour ago so it hasn't gone through yet.

This is my first contribution, I followed the guide but please let me know if I missed anything. Thanks!

[Mariatta]

New changeset 8b5fa28 by Mariatta (nathankerr96) in branch 'master':
bpo-32720: Fixed the definition for width and precision in format mini-language doc (GH-5482)
8b5fa28

[Mariatta]

New changeset 133514e by Mariatta (Miss Islington (bot)) in branch '3.7':
bpo-32720: Fixed the definition for width and precision in format mini-language doc (GH-5482) (GH-5524)
133514e

[Mariatta]

New changeset 3bd749b by Mariatta (Miss Islington (bot)) in branch '3.6':
bpo-32720: Fixed the definition for width and precision in format mini-language doc (GH-5482) (GH-5525)
3bd749b

[serhiy-storchaka]

What about arg_name and element_index?

>>> '{}'.format(123)
'123'
>>> '{0}'.format(123)
'123'
>>> '{0x0}'.format(123)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: '0x0'
>>> '{0_0}'.format(123)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: '0_0'
>>> '{0[0]}'.format([123])
'123'
>>> '{0[0x0]}'.format([123])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list indices must be integers or slices, not str
>>> '{0[0_0]}'.format([123])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list indices must be integers or slices, not str

[ncoghlan]

I didn't think to check those - it looks like they have the same problem with the same fix (i.e. the actual syntax is "digit+").

[Mariatta]

New changeset 7a561af by Mariatta in branch 'master':
bpo-32720: Fixed the replacement field grammar documentation. (GH-5544)
7a561af

[Mariatta]

New changeset a747cf6 by Mariatta (Miss Islington (bot)) in branch '3.7':
bpo-32720: Fixed the replacement field grammar documentation. (GH-5544) (GH-5546)
a747cf6