150 lines
4.3 KiB
Plaintext
150 lines
4.3 KiB
Plaintext
PEP: 321
|
||
Title: Date/Time Parsing and Formatting
|
||
Version: $Revision$
|
||
Last-Modified: $Date$
|
||
Author: A.M. Kuchling <amk@amk.ca>
|
||
Status: Withdrawn
|
||
Type: Standards Track
|
||
Content-Type: text/x-rst
|
||
Created: 16-Sep-2003
|
||
Python-Version: 2.4
|
||
Post-History:
|
||
|
||
|
||
Abstract
|
||
========
|
||
|
||
Python 2.3 added a number of simple date and time types in the
|
||
``datetime`` module. There's no support for parsing strings in various
|
||
formats and returning a corresponding instance of one of the types.
|
||
This PEP proposes adding a family of predefined parsing function for
|
||
several commonly used date and time formats, and a facility for generic
|
||
parsing.
|
||
|
||
The types provided by the ``datetime`` module all have
|
||
``.isoformat()`` and ``.ctime()`` methods that return string
|
||
representations of a time, and the ``.strftime()`` method can be used
|
||
to construct new formats. There are a number of additional
|
||
commonly-used formats that would be useful to have as part of the
|
||
standard library; this PEP also suggests how to add them.
|
||
|
||
|
||
Input Formats
|
||
=======================
|
||
|
||
Useful formats to support include:
|
||
|
||
* `ISO8601`_
|
||
* ARPA/:rfc:`2822`
|
||
* `ctime`_
|
||
* Formats commonly written by humans such as the American
|
||
"MM/DD/YYYY", the European "YYYY/MM/DD", and variants such as
|
||
"DD-Month-YYYY".
|
||
* CVS-style or tar-style dates ("tomorrow", "12 hours ago", etc.)
|
||
|
||
XXX The Perl `ParseDate.pm`_ module supports many different input formats,
|
||
both absolute and relative. Should we try to support them all?
|
||
|
||
Options:
|
||
|
||
1) Add functions to the ``datetime`` module::
|
||
|
||
import datetime
|
||
d = datetime.parse_iso8601("2003-09-15T10:34:54")
|
||
|
||
2) Add class methods to the various types. There are already various
|
||
class methods such as ``.now()``, so this would be pretty natural.::
|
||
|
||
import datetime
|
||
d = datetime.date.parse_iso8601("2003-09-15T10:34:54")
|
||
|
||
3) Add a separate module (possible names: date, date_parse, parse_date)
|
||
or subpackage (possible names: datetime.parser) containing parsing
|
||
functions::
|
||
|
||
import datetime
|
||
d = datetime.parser.parse_iso8601("2003-09-15T10:34:54")
|
||
|
||
|
||
Unresolved questions:
|
||
|
||
* Naming convention to use.
|
||
* What exception to raise on errors? ValueError, or a specialized exception?
|
||
* Should you know what type you're expecting, or should the parsing figure
|
||
it out? (e.g. ``parse_iso8601("yyyy-mm-dd")`` returns a ``date`` instance,
|
||
but parsing "yyyy-mm-ddThh:mm:ss" returns a ``datetime``.) Should
|
||
there be an option to signal an error if a time is provided where
|
||
none is expected, or if no time is provided?
|
||
* Anything special required for I18N? For time zones?
|
||
|
||
|
||
Generic Input Parsing
|
||
=======================
|
||
|
||
Is a strptime() implementation that returns ``datetime`` types sufficient?
|
||
|
||
XXX if yes, describe strptime here. Can the existing pure-Python
|
||
implementation be easily retargeted?
|
||
|
||
|
||
Output Formats
|
||
=======================
|
||
|
||
Not all input formats need to be supported as output formats, because it's
|
||
pretty trivial to get the ``strftime()`` argument right for simple things
|
||
such as YYYY/MM/DD. Only complicated formats need to be supported; :rfc:`2822`
|
||
is currently the only one I can think of.
|
||
|
||
Options:
|
||
|
||
1) Provide predefined format strings, so you could write this::
|
||
|
||
import datetime
|
||
d = datetime.datetime(...)
|
||
print d.strftime(d.RFC2822_FORMAT) # or datetime.RFC2822_FORMAT?
|
||
|
||
2) Provide new methods on all the objects::
|
||
|
||
d = datetime.datetime(...)
|
||
print d.rfc822_time()
|
||
|
||
|
||
Relevant functionality in other languages includes the `PHP date`_
|
||
function (Python implementation by Simon Willison at
|
||
http://simon.incutio.com/archive/2003/10/07/dateInPython)
|
||
|
||
|
||
References
|
||
==========
|
||
|
||
.. _ISO8601: http://www.cl.cam.ac.uk/~mgk25/iso-time.html
|
||
|
||
.. _ParseDate.pm: http://search.cpan.org/author/MUIR/Time-modules-2003.0211/lib/Time/ParseDate.pm
|
||
|
||
.. _ctime: http://www.opengroup.org/onlinepubs/007908799/xsh/asctime.html
|
||
|
||
.. _PHP date: http://www.php.net/date
|
||
|
||
Other useful links:
|
||
|
||
http://www.egenix.com/files/python/mxDateTime.html
|
||
http://ringmaster.arc.nasa.gov/tools/time_formats.html
|
||
http://www.thinkage.ca/english/gcos/expl/b/lib/0tosec.html
|
||
https://moin.conectiva.com.br/DateUtil
|
||
|
||
|
||
Copyright
|
||
=========
|
||
|
||
This document has been placed in the public domain.
|
||
|
||
|
||
|
||
..
|
||
Local Variables:
|
||
mode: indented-text
|
||
indent-tabs-mode: nil
|
||
sentence-end-double-space: t
|
||
fill-column: 70
|
||
End:
|