justnow

justnow is a systemd.timer inspired event parser in pure Python. The library consists of a lark grammar definition and some code to parse and generate datetimes.

Usage

Below is a snippet of the basic usage.

import datetime

from justnow.parser import EventParser

reference_date = datetime.datetime(2020, 1, 1)

# "sat *-*-* 14:00:00" => Generate all Saturdays at 14:00:00
parser = EventParser("sat *-*-* 14:00:00", reference_date=reference_date)

next(parser)  # datetime.datetime(2020, 1, 4, 14, 0)

# "sat *-02-29" => Generate all Saturdays which occur on a leap year
parser = EventParser("sat *-02-29", reference_date=reference_date)

list(parser.get_next_n(limit=2))  # [datetime.datetime(2020, 2, 29, 0, 0), datetime.datetime(2048, 2, 29, 0, 0)]

The justnow grammar defines a time event and is made of up 3 sections:

Weekday section

This section allows for a comma separated list of weekday names and weekday ranges.

Weekday names

The following are valid tokens for the weekday section:

• mon
• tue
• wed
• thu
• fri
• Mon
• Tue
• Wed
• Thu
• Fri
• monday
• tuesday
• wednesday
• thursday
• friday

Weekday ranges

A weekday range consists of two day names separated by two full stops.

For example mon..wed will evaluate into mon, tue and wed.

Date section

The date section is made up of 3 sub sections, namely:

• A year section
• A month section
• A day section

Each of the above sub sections can be either:

• One of more fixed length strings made up of integers separated by a comma. The length is 4 for years and 2 for months and days.
• A wildcard *

Time section

The time section is made up of 3 sub sections, namely:

• A hour section
• A minute section
• A second section

Each of the above sub sections can be either:

• One of more strings made up of 2 integers separated by a comma.
• A wildcard *

Named Events

justnow also supports a set of built in named events including:

• @minutely
• @hourly
• @daily
• @monthly
• @weekly
• @yearly
• @quarterly
• @semiannually
• @annually