strptime(.., '%c') fails to parse output of strftime('%c', ..) in some locales

[abalkin]

BPO	8957
Nosy	@abalkin, @vstinner, @ezio-melotti
Dependencies	bpo-8915: Use locale.nl_langinfo in _strptime
Files	strptime-locale-bug.c: Working C code strptime-locale-bug.py: Failing python code cfmt.py issue8957.py3k.1.patch

^{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 2010-06-09.20:24:38.889>
labels = ['extension-modules', 'type-bug', '3.7']
title = "strptime(.., '%c') fails to parse output of strftime('%c', ..) in some locales"
updated_at = <Date 2016-09-26.21:29:29.654>
user = 'https://github.com/abalkin'

bugs.python.org fields:

activity = <Date 2016-09-26.21:29:29.654>
actor = 'belopolsky'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2010-06-09.20:24:38.889>
creator = 'belopolsky'
dependencies = ['8915']
files = ['17601', '17602', '20358', '20412']
hgrepos = []
issue_num = 8957
keywords = ['patch']
message_count = 18.0
messages = ['107413', '125966', '125968', '126043', '126045', '126055', '126057', '126059', '126084', '126235', '126313', '126316', '126339', '126340', '126345', '126347', '126358', '221924']
nosy_count = 4.0
nosy_names = ['belopolsky', 'vstinner', 'ezio.melotti', 'rpetrov']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue8957'
versions = ['Python 3.7']

Linked PRs

• gh-53203: Fix strptime() for %c and %x formats on many locales #124946
• gh-53203: Improve tests for strptime() #125090
• [3.13] gh-53203: Improve tests for strptime() (GH-125090) #125091
• [3.12] gh-53203: Improve tests for strptime() (GH-125090) #125093
• [3.13] gh-53203: Fix strptime() for %c and %x formats on many locales (GH-124946) #125369
• [3.12] gh-53203: Fix strptime() for %c and %x formats on many locales (GH-124946) #125370
• gh-53203: Fix strptime() for %c, %x and %X formats on many locales #125406
• [3.13] gh-53203: Fix strptime() for %c, %x and %X formats on many locales (GH-125406) #125454
• gh-53203: Fix strptime() tests for %X on glibc < 2.29 #125469
• [3.12] gh-53203: Fix strptime() for %c, %x and %X formats on many locales (GH-125406) (GH-125454) #125483
• gh-53203: Fix test_strptime on Solaris #125785
• [3.13] gh-53203: Fix test_strptime on Solaris (GH-125785) #125806
• [3.12] gh-53203: Fix test_strptime on Solaris (GH-125785) #125807
• gh-53203: Fix strptime() for %c, %x and %X formats on some locales #135971
• [3.14] gh-53203: Fix strptime() for %c, %x and %X formats on some locales (GH-135971) #136019
• [3.13] gh-53203: Fix strptime() for %c, %x and %X formats on some locales (GH-135971) #136020

[abalkin]

The following code:

import locale, time
locale.setlocale(locale.LC_ALL, "fr_FR.UTF-8")
t = time.localtime()
s = time.strftime('%c', t)
time.strptime('%c', s)

Raises

ValueError: time data '%c' does not match format 'Mer 9 jui 16:14:46 2010'

in any locale where month follows day in '%c' format. Note that attached C code works as expected on my OSX laptop.

I wonder it it would make sense to call platform strptime where available? I wonder if platform support for strptime has improved since 2002 when _strptime.py was introduced.

[abalkin]

Adding bpo-8915 as a dependency because deducing D_T_FMT locale setting from strftime output seems impossible:

>>> locale.nl_langinfo(locale.D_T_FMT)
'%a %b %e %H:%M:%S %Y'

[abalkin]

Victor,

You may be interested because your native language is implicated. :-)

[rpetrov]

time.strptime(s, '%c' ) ?

[abalkin]

time.strptime(s, '%c' ) ?

Oh my. It certainly took a long time to recognize a silly mistake!

Thanks.

[abalkin]

My tests were wrong but the problem does exist. I am attaching a script that tests strptime(.., '%c') for all locales installed on my system (an unmodified US Mac OS X 10.6.6).

The only failing locale that I recognize is Hebrew (he_IL). Eli, what do you think about this?

 
$ ./python.exe cfmt.py 
am_ET [ማክሰ ጃንዩ 11 18:56:18 2011] %A %B %d %H:%M:%S %Y != %a %b %e %H:%M:%S %Y
et_EE [T, 11. jaan 2011. 18:56:18] %a, %d. %B %Y. %H:%M:%S != %a, %d. %b %Y. %T
he_IL [EST 18:56:18 2011 ינו 11 ג'] %Z %H:%M:%S %Y %B %d %a != %Z %H:%M:%S %Y %b %d %a

[rpetrov]

• %T is equal for %H:%M:%S
• locales with %A and %B are broken on this platform as %c is "Appropriate date and time representation (%c) with abbreviations"