pycron: Cron-like Parser

Warnings

• breaking Version 3.0.0 dropped support for Python 2.7 and Python 3.4. Users on these older Python versions must remain on `pycron < 3.0.0`.
  Fix: Upgrade Python to a supported version (>=3.9, <4.0) or pin `pycron` to an older version like `pycron<3.0.0`.
• breaking Version 3.1.0 included updates to the DOM (Day of Month) and DOW (Day of Week) parsing logic. While intended for correctness, this might subtly change the interpretation of certain complex or edge-case cron expressions, potentially leading to different match outcomes.
  Fix: Thoroughly test existing cron expressions when upgrading to `pycron >= 3.1.0` to ensure continued expected behavior, especially for expressions involving specific days of the month or week combinations.
• gotcha pycron supports both timezone-aware and naive datetime objects. However, mixing them or not consistently handling timezones can lead to unexpected matches, particularly when cron expressions refer to specific times (e.g., '0 0 * * *' for midnight). The library itself does not perform timezone conversions.
  Fix: Ensure that the datetime objects passed to `is_now` or `has_been` are consistently timezone-aware (preferably UTC) or consistently naive, matching the intended timezone context of your cron expressions.
• gotcha pycron 3.x strictly requires Python versions >=3.9 and <4.0. Attempting to install or run on Python 3.8 or older, or Python 4.0 and newer (when released) without explicit support, will result in installation failures or runtime errors.
  Fix: Verify your Python environment meets the `>=3.9, <4.0` requirement before installing `pycron`.

Install

• pip install pycron Install pycron

Imports

• is_now

  from pycron import is_now

• has_been

  from pycron import has_been

  Used for 'anacron' style checks to see if conditions have been met since a past datetime.

Quickstart

Demonstrates how to use `is_now` to check if a cron expression matches a given datetime (or the current time), and `has_been` for checking if a condition was met within a time range.

import datetime
from pycron import is_now, has_been

# Check if current time (or a specific datetime) matches a cron string
# This example checks if it's currently every minute
matches_every_minute = is_now('* * * * *')
print(f"Matches every minute (current time): {matches_every_minute}")

# Check for a specific time, e.g., 9:30 AM every weekday
specific_dt = datetime.datetime(2023, 10, 26, 9, 30, 0) # Thursday
matches_specific_time = is_now('30 9 * * 1-5', specific_dt)
print(f"Matches 9:30 AM on a weekday (2023-10-26 09:30): {matches_specific_time}")

# Using has_been (anacron style)
# Check if '0 0 * * *' (midnight) has occurred since an hour ago
now = datetime.datetime.now()
one_hour_ago = now - datetime.timedelta(hours=1)
midnight_occurred = has_been('0 0 * * *', one_hour_ago, now)
print(f"Midnight occurred between {one_hour_ago.strftime('%H:%M')} and {now.strftime('%H:%M')}: {midnight_occurred}")