isoperiod

ISO 8601 period and duration arithmetic, including offsets from the natural boundary, for defining sampling resolution and periodicity in timeseries data

Features

• ISO 8601 durations - build a period from "PT15M", "P1D" or "P1Y".
• Offsets - shift every interval boundary off its natural position, for hydrological days ("P1D+T9H") and water years ("P1Y+9MT9H").
• Origins - pin the grid to a chosen datetime with the "2024-01-01/P7D" form.
• Ordinals - every interval on the timeline has an integer ordinal, so flooring, stepping and grouping are integer arithmetic, calendar months included.
• Alignment - check that a timestamp sits on a period boundary, and whether one period nests cleanly inside another.
• No runtime dependencies - pure Python on top of datetime, with helpers for handing periods to Polars.

Installation

pip install isoperiod

or with uv:

uv add isoperiod

See the documentation for a quick start, the concepts behind the API, and the full reference.

License

This project is licensed under the MIT license.

Contributing

Contributions are welcome. Please feel free to submit a Pull Request.

1. Clone the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Please make sure your code passes all tests and follows the coding style before submitting a PR. See developer setup below for more information.

Developer Setup

This is for active development on the isoperiod package itself.

Requirements

Install uv

Official instructions

Clone the repository

git clone https://github.com/NERC-CEH/isoperiod.git
cd isoperiod

Setting up and activating a virtual environment

uv sync
source .venv/bin/activate

Linting

Linting uses ruff using the config in pyproject.toml

ruff check --fix

Formatting

Formating uses ruff using the config in pyproject.toml which follows the default black settings.

ruff format .

Testing

Testing is done using pytest and tests are in the /tests directory.

pytest

Pre commit hooks

Run below to setup the pre-commit hooks.

git config --local core.hooksPath .githooks/

This will set this repo up to use the git hooks in the .githooks/ directory. The hook runs ruff format --check and ruff check to prevent commits that are not formatted correctly or have errors. The hook intentionally does not alter the files, but informs the user which command to run.

Documentation

For full documentation, visit https://nerc-ceh.github.io/isoperiod/

To build the documentation locally:

# Install documentation dependencies (but they are included by default)
uv sync --group docs

# Build the documentation
cd docs
make html

# View documentation
open _build/html/index.html

Citation

If you use this software, please cite it using the metadata in CITATION.cff.

Built with Cookiecutter and the NERC-CEH/fdri-cookiecutter-templates template.