Not matched behavior within printf style bytes formatting

[wooyoo]

BPO	29000
Nosy	@bitdancer, @ethanfurman, @serhiy-storchaka
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	bytes-format-oct-alt-zero.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2016-12-17.20:18:12.502>
created_at = <Date 2016-12-17.13:41:04.667>
labels = ['interpreter-core', 'type-bug', '3.7']
title = 'Not matched behavior within printf style bytes formatting'
updated_at = <Date 2017-03-31.16:36:28.705>
user = 'https://bugs.python.org/wooyoo'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:28.705>
actor = 'dstufft'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2016-12-17.20:18:12.502>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2016-12-17.13:41:04.667>
creator = 'woo yoo'
dependencies = []
files = ['45943']
hgrepos = []
issue_num = 29000
keywords = ['patch']
message_count = 9.0
messages = ['283485', '283486', '283488', '283489', '283491', '283499', '283502', '283513', '283514']
nosy_count = 6.0
nosy_names = ['r.david.murray', 'docs@python', 'ethan.furman', 'python-dev', 'serhiy.storchaka', 'woo yoo']
pr_nums = ['552']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue29000'
versions = ['Python 3.5', 'Python 3.6', 'Python 3.7']

[wooyoo]

Per the documentation,"The alternate form causes a leading octal specifier ('0o') to be inserted before the first digit", However the actual behavior didn't conform to the principle.

Code:

>>b'%#07o' % 34

Output: b'0000o42'

[wooyoo]

The link is https://docs.python.org/3.5/library/stdtypes.html#printf-style-bytes-formatting

[bitdancer]

The documentation matches the behavior. In this context "the first digit" is the 4. The leading zeros are the pad fill. Now, whether this is *useful* behavior or not is a separate question :) And yes, the docs could be clarified on this point either way.

[wooyoo]

Make a slight change to my code, which becomes b'%#07x' % 34, the weird situation appears.

[serhiy-storchaka]

This is not documentation issue, but a bug in formatting octals in bytes.

>>> '%#07x' % 123
'0x0007b'
>>> b'%#07x' % 123
b'0x0007b'
>>> '%#07o' % 123
'0o00173'
>>> b'%#07o' % 123
b'000o173'
     ^

[serhiy-storchaka]

Proposed patch fixes this inconsistency.

[bitdancer]

OK, that makes sense. Patch looks good to me.

[python-dev]

New changeset 96d728c14267 by Serhiy Storchaka in branch '3.5':
Issue bpo-29000: Fixed bytes formatting of octals with zero padding in alternate
https://hg.python.org/cpython/rev/96d728c14267

New changeset 29c9c414c310 by Serhiy Storchaka in branch '3.6':
Issue bpo-29000: Fixed bytes formatting of octals with zero padding in alternate
https://hg.python.org/cpython/rev/29c9c414c310

New changeset 4e55e011dd80 by Serhiy Storchaka in branch 'default':
Issue bpo-29000: Fixed bytes formatting of octals with zero padding in alternate
https://hg.python.org/cpython/rev/4e55e011dd80

[serhiy-storchaka]

Thanks David.