[issue12886] datetime.strptime parses input wrong

[Serhiy Storchaka]

Change by Serhiy Storchaka :


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versions: +Python 3.10, Python 3.6, Python 3.7, Python 3.8, Python 3.9 -Python 
2.6, Python 2.7

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[issue12886] datetime.strptime parses input wrong

[Ezio Melotti]

Changes by Ezio Melotti ezio.melo...@gmail.com:


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nosy: +belopolsky

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[issue12886] datetime.strptime parses input wrong

[Ezio Melotti]

Changes by Ezio Melotti ezio.melo...@gmail.com:


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nosy: +ezio.melotti
stage:  - patch review

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[issue12886] datetime.strptime parses input wrong

[Hieu Nguyen]

Hieu Nguyen added the comment:

I have attached a patch for this issue, so that if the format of the input 
argument doesn't match ISO 8601 format, it will return ValueError: time data 
xxx does not match format xxx.

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keywords: +patch
nosy: +hieu.nguyen
Added file: http://bugs.python.org/file27675/issue12886.patch

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[issue12886] datetime.strptime parses input wrong

[Hieu Nguyen]

Hieu Nguyen added the comment:

Attached another patch for clearer test cases against this fix (as suggested 
from Ezio).

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Added file: http://bugs.python.org/file27688/issue12886.patch

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[issue12886] datetime.strptime parses input wrong

[Heiðar Rafn Harðarson]

Heiðar Rafn Harðarson heidar.r...@hrolfsskali.net added the comment:

My understanding of the python documentation and the ISO 8601 standard is that 
the digits in a timestamp representing hours, minutes and seconds shall always 
be in pairs of 2 digits (hh, mm, ss), i.e. when a number is less than 10 it 
should be preceded by 0. 
In the example I give, the minute figure is split between minutes and seconds 
by the  python library function which I consider a bug: 
datetime.datetime.strptime('20110817T1234','%Y%m%dT%H%M%S') 
gives
datetime.datetime(2011, 8, 17, 12, 3, 4)

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[issue12886] datetime.strptime parses input wrong

[Heiðar Rafn Harðarson]

Heiðar Rafn Harðarson heidar.r...@hrolfsskali.net added the comment:

This issue is also discussed here: http://bugs.python.org/issue5979

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[issue12886] datetime.strptime parses input wrong

[Heiðar Rafn Harðarson]

New submission from Heiðar Rafn Harðarson heidar.r...@hrolfsskali.net:

When using datetime.strptime or time.strptime to parse string representing 
timestamp with the format string '%Y%m%dT%H%M%S' then a strange behavior 
happens when the input string does not contain the seconds: the minute part is 
split and first digit used as minutes and second digit as seconds !

According to documentation %M shall contain Minute as a decimal number [00,59] 
and %S shall contain Second as a decimal number [00,61]

Here are few examples to show this:
--
Python 2.6.6 (r266:84292, Sep 15 2010, 16:22:56) 
[GCC 4.4.5] on linux2
Type help, copyright, credits or license for more information.
 import datetime
 datetime.datetime.strptime('20110817T1234','%Y%m%dT%H%M%S')
datetime.datetime(2011, 8, 17, 12, 3, 4)
=ERROR no seconds in input string: minute=3, second=4
=I would expect exception ValueError or datetime.datetime(2011, 8, 17, 12, 34, 
00)

 datetime.datetime.strptime('20110817T123456','%Y%m%dT%H%M%S')
datetime.datetime(2011, 8, 17, 12, 34, 56)
=CORRECT

 datetime.datetime.strptime('20110817T123456','%Y%m%dT%H%M')
Traceback (most recent call last):
  File stdin, line 1, in module
  File /usr/lib/python2.6/_strptime.py, line 328, in _strptime
data_string[found.end():])
ValueError: unconverted data remains: 56
=CORRECT

 datetime.datetime.strptime('20110817T1234','%Y%m%dT%H%M')
datetime.datetime(2011, 8, 17, 12, 34)
= CORRECT

--
I have tested this with python 2.6 and 2.7
This also happens on when playing with %H%M format string and omit minutes from 
the input.

--
components: Library (Lib)
messages: 143400
nosy: heidar.rafn
priority: normal
severity: normal
status: open
title: datetime.strptime parses input wrong
type: behavior
versions: Python 2.6, Python 2.7

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[issue12886] datetime.strptime parses input wrong

[STINNER Victor]

STINNER Victor victor.stin...@haypocalc.com added the comment:

 ERROR no seconds in input string: minute=3, second=4

If you specificy %S in the format string, strptime() *requires* seconds. If 
seconds are optional in your format, you should call strptime() twice: first 
without '%S', then with '%S' if the first failed.

I don't consider your examples as bugs.

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nosy: +haypo

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[issue12886] datetime.strptime parses input wrong

[STINNER Victor]

STINNER Victor victor.stin...@haypocalc.com added the comment:

Example:
---
import datetime

def test(text):
try:
d = datetime.datetime.strptime(text, '%Y%m%dT%H%M')
except ValueError:
pass
else:
print(%s without seconds = %s % (text, d))
return
d = datetime.datetime.strptime(text, '%Y%m%dT%H%M%S')
print(%s with seconds = %s % (text, d))

test('20110817T1234')
test('20110817T12345')
test('20110817T123456')
---

Output:

20110817T1234 without seconds = 2011-08-17 12:34:00
20110817T12345 with seconds = 2011-08-17 12:34:05
20110817T123456 with seconds = 2011-08-17 12:34:56

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