once-only 1.0.0

Run a python script or function only once in a given time frame.

once_only

Run a python script or function only once in a given time frame.

If, for example, you have a script or service which might be called frequently, but you want to report errors only once daily to not annoy people too much, once_only is the library for you.

Quickstart

Suppose you want your script to complain, but not more than once a day. once_only.daily is the tool you need:

import once_only

@once_only.daily
def complain():
    print("This is not right!")

Now you can run complain as often as you want, from the same python script or from others, it will only be run at most once a day, so that at least 24 hours are between two complaints.

If you want to complain more or less often, there are other variants:

object	time delta
once_only.weekly	1 week
once_only.daily	1 day
once_only.hourly	1 hour
once_only.minutely	1 minute
once_only.Once()	custom datetime.timedelta

Advanced Usage

Instead of using a once_only.Once object as a decorator, you can also access it directly via the check_ready() and check_ready_trigger() functions:

import once_only
import datetime

once_every_two_hours = once_only.Once(datetime.timedelta(hours=2))

if once_every_two_hours.check_ready():
    print("More than two hours have passed since last run!")

if not_a_dry_run and once_every_two_hours.check_ready_trigger():
    print("Triggering timer and running!")

Note that all instances of once_only.Once with the same time delta share the same timer, but those with different time deltas don’t share the timer. So, if you have never run anything before, this:

import once_only
import datetime

@once_only.minutely
def run_minutely():
    print("minutely")

@once_only.hourly
def run_hourly():
    print("hourly")

@once_only.Once(datetime.timedelta(minutes=60))
def run_every_60_minutes():
    print("60 minutes")

run_minutely()
run_hourly()
run_every_60_minutes()

will print “minutely” and “hourly”, but not “60 minutes” because 60 minutes is the same as one hour, so the 60 minutes timer will already be triggered by run_hourly and run_every_60_minutes will not be run.

Further documentation can be found at: https://once_only.readthedocs.io.

License

Copyright 2022, Potsdam-Institut für Klimafolgenforschung e.V.

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Changelog

1.0.0 (2022-09-16)

• Initial commit.

• once_only.Once class implemented, with direct access API and decorator functionalities.

• Add Quickstart documentation.