Metadata-Version: 2.4 Name: cronsim Version: 2.7 Summary: Cron expression parser and evaluator Author-email: Pēteris Caune Project-URL: Repository, https://github.com/cuu508/cronsim.git Project-URL: Issues, https://github.com/cuu508/cronsim/issues Project-URL: Changelog, https://github.com/cuu508/cronsim/blob/main/CHANGELOG.md Keywords: cron,cronjob,crontab,schedule Classifier: Development Status :: 5 - Production/Stable Classifier: Intended Audience :: Developers Classifier: License :: OSI Approved :: BSD License Classifier: Operating System :: OS Independent Classifier: Programming Language :: Python Classifier: Programming Language :: Python :: 3 Classifier: Topic :: Software Development :: Libraries :: Python Modules Classifier: Typing :: Typed Requires-Python: >=3.10 Description-Content-Type: text/markdown License-File: LICENSE Dynamic: license-file # CronSim [![Tests](https://github.com/cuu508/cronsim/actions/workflows/pytest.yml/badge.svg)](https://github.com/cuu508/cronsim/actions/workflows/pytest.yml) Cron Sim(ulator), a cron expression parser and evaluator. Works with Python 3.10+. CronSim is written for and being used in [Healthchecks](https://github.com/healthchecks/healthchecks/) (a cron job monitoring service). Development priorities: * Correctness. CronSim tries to match Debian's cron as closely as possible, including its quirky behaviour during DST transitions. * Readability. Prefer simple over clever. * Minimalism. Don't implement features that Healthchecks will not use. ## Installation ``` pip install cronsim ``` ## Usage ```python from datetime import datetime from cronsim import CronSim it = CronSim("0 0 * 2 MON#5", datetime(2020, 1, 1)) for x in range(0, 5): print(next(it)) ``` Produces: ``` 2044-02-29 00:00:00 2072-02-29 00:00:00 2112-02-29 00:00:00 2140-02-29 00:00:00 2168-02-29 00:00:00 ``` To iterate backwards in time, add `reverse=True` in the constructor: ```python from datetime import datetime from cronsim import CronSim it = CronSim("0 0 * 2 MON#5", datetime(2020, 1, 1), reverse=True) print(next(it)) ``` Produces: ``` 2016-02-29 00:00:00 ``` If CronSim receives an invalid cron expression, it raises `cronsim.CronSimError`: ```python from datetime import datetime from cronsim import CronSim CronSim("123 * * * *", datetime(2020, 1, 1)) ``` Produces: ``` cronsim.cronsim.CronSimError: Bad minute ``` If CronSim cannot find a matching datetime in the next 50 years from the start date or from the previous match, it stops iteration by raising `StopIteration`: ```python from datetime import datetime from cronsim import CronSim # Every minute of 1st and 21st of month, # if it is also the *last Monday* of the month: it = CronSim("* * */20 * 1L", datetime(2020, 1, 1)) print(next(it)) ``` Produces: ``` StopIteration ``` ## CronSim Works With zoneinfo CronSim starting from version 2.0 is designed to work with timezones provided by the zoneinfo module. A previous version, CronSim 1.0, was designed for pytz and relied on its following non-standard features: * the non-standard `is_dst` flag in the `localize()` method * the `pytz.AmbiguousTimeError` and `pytz.NonExistentTimeError` exceptions * the `normalize()` method ## Supported Cron Expression Features CronSim aims to match [Debian's cron implementation](https://salsa.debian.org/debian/cron/-/tree/master/) (which itself is based on Paul Vixie's cron, with modifications). If CronSim evaluates an expression differently from Debian's cron, that's a bug. CronSim is open to adding support for non-standard syntax features, as long as they don't conflict or interfere with the standard syntax. ## DST Transitions CronSim handles Daylight Saving Time transitions the same as Debian's cron. Debian has special handling for jobs with a granularity greater than one hour: ``` Local time changes of less than three hours, such as those caused by the start or end of Daylight Saving Time, are handled specially. This only applies to jobs that run at a specific time and jobs that are run with a granularity greater than one hour. Jobs that run more fre- quently are scheduled normally. If time has moved forward, those jobs that would have run in the inter- val that has been skipped will be run immediately. Conversely, if time has moved backward, care is taken to avoid running jobs twice. ``` See test cases in `test_cronsim.py`, `TestDstTransitions` class for examples of this special handling. ## Cron Expression Feature Matrix | Feature | Debian | Quartz | croniter | cronsim | | ------------------------------------ | :----: | :----: | :------: | :-----: | | Seconds in the 6th field | No | Yes | Yes | Yes | | "L" as the day-of-month | No | Yes | Yes | Yes | | "LW" as the day-of-month | No | Yes | No | Yes | | "L" in the day-of-week field | No | Yes | No | Yes | | Nth weekday of month | No | Yes | Yes | Yes | **Seconds in the 6th field**: an optional sixth field specifying seconds. Supports the same syntax features as the minutes field. Quartz Scheduler and cronsim expects seconds in the first field, croniter can be configured to use the first or the last field as seconds. cronsim example: `*/15 * * * * *` (every 15 seconds). **"L" as the day-of-month**: support for the "L" special character in the day-of-month field. Interpreted as "the last day of the month". Example: `0 0 L * *` (at the midnight of the last day of every month). **"LW" as the day-of-month**: support for the "LW" special value in the day-of-month field. Interpreted as "the last weekday (Mon-Fri) of the month". Example: `0 0 LW * *` (at the midnight of the last weekday of every month). **"L" in the day-of-week field**: support for the "{weekday}L" syntax. For example, "5L" means "the last Friday of the month". Example: `0 0 * * 6L` (at the midnight of the last Saturday of every month). **Nth weekday of month**: support for "{weekday}#{nth}" syntax. For example, "MON#1" means "first Monday of the month", "MON#2" means "second Monday of the month". Example: `0 0 * * MON#1` (at midnight of the first monday of every month). ## The `explain()` Method Starting from version 2.4, the CronSim objects have an `explain()` method which generates a text description of the supplied cron expression. ```python from datetime import datetime from cronsim import CronSim expr = CronSim("*/5 9-17 * * *", datetime.now()) print(expr.explain()) ``` Outputs: ``` Every fifth minute from 09:00 through 17:59 ``` Notes: * The text descriptions are available in English only. * The text descriptions use the 24-hour time format ("23:00" instead of "11:00 PM"). For examples of generated descriptions see `tests/test_explain.py`.