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ParseTime

ParseTime is a simple Python extension module that simply wraps the parsetime() function that is used internally by the familiar "at" command that is typically found on Unix systems. This allows a programmer to parse a complicated expression that represents a particular point in time. ParseTime was originally created for the sole purpose of developing the sleeptill command, which was, in turn, merely created to allow the user to schedule one-time jobs that should be executed in the foreground of a terminal (instead of in the background, as is done by "at"). You could, of course, use the plain old "sleep" command to do the same thing, if you were willing to perform some rather annoying arithmetic.

DateUtil is another Python module that also provides the capability of parsing date and time strings. DateUtil is more sophisticated, and contains many other features related to date, time, and calendar data. However, ParseTime has the small advantage of using the same familiar syntax as the "at" command.

Download

The following releases are available:

Installation

The library code from a lex implementation must be available to build this module. Installing flex should satisfy this requirement on Unix systems. I don't know of any lex implementations for Windows or MacOS Classic, so if you want to build this on those platforms, you're on your own.

Your Python installation must also include the tools required for building Python extension modules (i.e. distutils). Many Linux distributions put these tools in a package that is separate from the main Python package. For instance, on Debian the "python-dev" package must be installed.

After unpacking the source distribution archive, run the command "python setup.py install" as root. If you are on a Unix system and you don't want to install the module system-wide, use "python setup.py install --home=~" instead. See Installing Python Modules for more advanced information on how to install third-party Python modules.

Usage

This Python module contains only a single function, named "parsetime". It accepts a variable number of string arguments which are joined to form a time specification expression. This expression is evaluated and (if valid) will be returned in the form of an integer that counts the number of seconds between the beginning of the epoch and the time specified. The syntax of a time specification is the same as that used for the arguments to the "at" command that is commonly found on Unix systems.

For example:

>>> import parsetime
>>> parsetime.parsetime('7AM Mar 24 2000')
953874000
>>> import time
>>> time.ctime(parsetime.parsetime('7AM Mar 24 2000'))
'Fri Mar 24 07:00:00 2000'
>>> time.ctime(parsetime.parsetime('7AM', 'Mar', '24', '2000'))
'Fri Mar 24 07:00:00 2000'
>>> time.ctime(parsetime.parsetime('4pm + 3 days'))
'Sun Jan  4 16:00:00 2004'
>>> time.ctime(parsetime.parsetime('next week'))
'Thu Jan  8 19:54:00 2004'
>>> time.ctime(parsetime.parsetime('3:15pm next Tuesday'))
'Tue Jan  6 15:15:00 2004'

Credits

I (Daniel Pearson) can only take credit for the code in parsetime.c, which merely binds the function to Python, and for the minimal work involved in extracting the time-parsing code from the rest of the "at" source code. The code that does the real hard work was written by the authors of "at", Thomas Koenig and David Parsons, and is bound by their copyright:

Copyright: 1993, 1994, 1995, 1996, 1997 (c) Thomas Koenig
           1993 (c) David Parsons

This program is free software, and can be redistributed and/or modified under the terms of the GNU General Public License (GPL), version 2.