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Test date/time against a time period expressed in a simple grammar

Project description

Timeswitch allows dates to be tested against a time range to see if they are contained within the time range. Time ranges are expressed using a simple grammar that supports absolute dates and times, repeating periods, greater, less than, between and exact match comparisons, and combinations of brackets and infix notation logical operators.

A time is made up of the following ordered components, with sensible defaults for components when omitted:

  • year: range expression with values 1-9999
  • month: range expression with integer values 1-12 or case insensitive jan, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec
  • day: range expression with either integer values 1-31 or case insensitive mon, tue, wed, thu, fri, sat, sun. When used with a month a weekday has an optional ordinal 1st, 2nd, 3rd, 4th or 5th prefix to indicate nth weekday in the month
  • hour-minute: range expression with two integer values separated by a colon 0-23:0-59
  • compound: range expression with all or partial non ambiguous sequences of year month day hour-minute values

The expected month, weekday and ordinal strings can be overriden if necessary using the API.

A time range expression is similar to Python array syntax:

  • - is any value
  • x is a value = x
  • x-y is a value x ≤ value ≤ y. Note that:
    • The expressions on either side of the - must specify the same rightmost elements, e.g 2017 jan - feb not 2017 jan - feb 12
    • The repeat period of the right hand side must be the same as or more frequent thant the first e.g jan - 2017 feb is not valid
    • For weekday ranges, Monday is considered the start of the week
  • -x is a value less than or equal to x
  • x- is a value greater than or equal to x

Time range expressions can be combined using and, or, not and ( ) to form nested expressions.

The empty string is always off. A dash is always on:

-

Always on from 1:30am on the 3rd of April 2017:

2017 apr 3 1:30 -

Always on every Friday on or after the 3rd of April 2017 (year and month can be omitted because ‘fri’ is unambiguously a weekday):

fri and 2017 apr 3 -

Always on every 1st Friday of the month on or after the 3rd of April 2017:

1st fri and 2017 apr 3 -

Always on every 1st or 3rd Friday of the month on or after the 3rd of April 2017:

(1st fri or 3rd fri) and 2017 apr 3 -

First Friday of the month between 6:30pm and 9:50pm:

1st fri 18:30-21:50

Thanksgiving, Christmas, Boxing Day and New Year’s Day:

nov 4th thu or dec 25 or dec 26 or jan 1

Normal operator precedence is not, and, or. Parenthesis can be used to change this:

not((jun or aug) and 2017)

Usage

A command line interface for timeswitch is available:

$ timeswitch
usage: timeswitch [-h] [-d] [-w] [-y] [-a] [-p] expression [date]
timeswitch: error: too few arguments
$ timeswitch "2017 jan 20 -"
on
$ echo $?
0
$ timeswitch "1972 dec 5 - 1975 nov 11"
off
$ echo $?
1
$

The --year, --week, and --day options provide helpful visualisations when developing and debugging timeswitch expressions.

To use the library directly in Python:

from timeswitch import timeswitch
from datetime import datetime

ts = timeswitch('2017 may 4 20:20 - 20:30')
print ts(datetime(2017, 5, 4, 20, 21))  # True
print ts(datetime(2017, 5, 4, 20, 31))  # False

timeswitch() accepts optional named months, weekdays and ordinal arguments. Each is an array of alternative literal strings used when parsing the corresponding date part, for example if you want to write ‘first wed’ instead of ‘1st wed’:

ts = timeswitch('first wed', ordinals='first second third fourth fifth'.split(' '))

Contributing

You may contribute to the project by logging issues through the project issue tracker or by submitting a pull request.

Development

A development environment may be setup like this:

git clone https://bitbucket.org/rocketboots/timeswitch.git
cd timeswitch
pip install -e .[test]
python setup.py nosetests

Contributions should include passing unit tests.

PyPI Registration

To support reStructuredText as PyPI expects, this document is automatically converted provided the Pandoc package is installed. On OS X,

brew install pandoc
pip install pypandoc twine
python setup.py sdist
twine register dist/timeswitch-*.tar.gz

Project details


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1.0.1

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1.0.0

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