Pooch: A friend to fetch your data files

Documentation (latest) (https://www.fatiando.org/pooch) •
Documentation (main branch) (https://www.fatiando.org/pooch/dev) •
Contributing (https://github.com/fatiando/pooch/blob/main/CONTRIBUTING.md) •
Contact (https://www.fatiando.org/contact/)

Part of the Fatiando a Terra (https://www.fatiando.org) project

## About

> Just want to download a file without messing with `requests` and `urllib`?
> Trying to add sample datasets to your Python package?
> **Pooch is here to help!**

*Pooch* is a **Python library** that can manage data by **downloading files**
from a server (only when needed) and storing them locally in a data **cache**
(a folder on your computer).

* Pure Python and minimal dependencies.
* Download files over HTTP, FTP, and from data repositories like Zenodo and figshare.
* Built-in post-processors to unzip/decompress the data after download.
* Designed to be extended: create custom downloaders and post-processors.

Are you a **scientist** or researcher? Pooch can help you too!

* Host your data on a repository and download using the DOI.
* Automatically download data using code instead of telling colleagues to do it themselves.
* Make sure everyone running the code has the same version of the data files.

## Projects using Pooch

[SciPy](https://github.com/scipy/scipy), 
[scikit-image](https://github.com/scikit-image/scikit-image),
[xarray](https://github.com/pydata/xarray),
[Ensaio](https://github.com/fatiando/ensaio),
[GemPy](https://github.com/cgre-aachen/gempy),
[MetPy](https://github.com/Unidata/MetPy),
[napari](https://github.com/napari/napari),
[Satpy](https://github.com/pytroll/satpy),
[yt](https://github.com/yt-project/yt),
[PyVista](https://github.com/pyvista/pyvista),
[icepack](https://github.com/icepack/icepack),
[histolab](https://github.com/histolab/histolab),
[seaborn-image](https://github.com/SarthakJariwala/seaborn-image),
[Open AR-Sandbox](https://github.com/cgre-aachen/open_AR_Sandbox),
[climlab](https://github.com/climlab/climlab),
[mne-python](https://github.com/mne-tools/mne-python),
[GemGIS](https://github.com/cgre-aachen/gemgis),
[SHTOOLS](https://github.com/SHTOOLS/SHTOOLS),
[MOABB](https://github.com/NeuroTechX/moabb),
[GeoViews](https://github.com/holoviz/geoviews),
[ScopeSim](https://github.com/AstarVienna/ScopeSim),
[Brainrender](https://github.com/brainglobe/brainrender),
[pyxem](https://github.com/pyxem/pyxem),
[cellfinder](https://github.com/brainglobe/cellfinder),
[PVGeo](https://github.com/OpenGeoVis/PVGeo),
[geosnap](https://github.com/oturns/geosnap),
[BioCypher](https://github.com/biocypher/biocypher),
[cf-xarray](https://github.com/xarray-contrib/cf-xarray),
[Scirpy](https://github.com/scverse/scirpy),
[rembg](https://github.com/danielgatis/rembg),
[DASCore](https://github.com/DASDAE/dascore),
[scikit-mobility](https://github.com/scikit-mobility/scikit-mobility),
[Py-ART](https://github.com/ARM-DOE/pyart),
[HyperSpy](https://github.com/hyperspy/hyperspy),
[RosettaSciIO](https://github.com/hyperspy/rosettasciio),
[eXSpy](https://github.com/hyperspy/exspy)


> If you're using Pooch, **send us a pull request** adding your project to the list.

## Example

For a **scientist downloading a data file** for analysis:

```python
import pooch
import pandas as pd

# Download a file and save it locally, returning the path to it.
# Running this again will not cause a download. Pooch will check the hash
# (checksum) of the downloaded file against the given value to make sure
# it's the right file (not corrupted or outdated).
fname_bathymetry = pooch.retrieve(
    url="https://github.com/fatiando-data/caribbean-bathymetry/releases/download/v1/caribbean-bathymetry.csv.xz",
    known_hash="md5:a7332aa6e69c77d49d7fb54b764caa82",
)

# Pooch can also download based on a DOI from certain providers.
fname_gravity = pooch.retrieve(
    url="doi:10.5281/zenodo.5882430/southern-africa-gravity.csv.xz",
    known_hash="md5:1dee324a14e647855366d6eb01a1ef35",
)

# Load the data with Pandas
data_bathymetry = pd.read_csv(fname_bathymetry)
data_gravity = pd.read_csv(fname_gravity)
```

For **package developers** including sample data in their projects:

```python
"""
Module mypackage/datasets.py
"""
import pkg_resources
import pandas
import pooch

# Get the version string from your project. You have one of these, right?
from . import version

# Create a new friend to manage your sample data storage
GOODBOY = pooch.create(
    # Folder where the data will be stored. For a sensible default, use the
    # default cache folder for your OS.
    path=pooch.os_cache("mypackage"),
    # Base URL of the remote data store. Will call .format on this string
    # to insert the version (see below).
    base_url="https://github.com/myproject/mypackage/raw/{version}/data/",
    # Pooches are versioned so that you can use multiple versions of a
    # package simultaneously. Use PEP440 compliant version number. The
    # version will be appended to the path.
    version=version,
    # If a version as a "+XX.XXXXX" suffix, we'll assume that this is a dev
    # version and replace the version with this string.
    version_dev="main",
    # An environment variable that overwrites the path.
    env="MYPACKAGE_DATA_DIR",
    # The cache file registry. A dictionary with all files managed by this
    # pooch. Keys are the file names (relative to *base_url*) and values
    # are their respective SHA256 hashes. Files will be downloaded
    # automatically when needed (see fetch_gravity_data).
    registry={"gravity-data.csv": "89y10phsdwhs09whljwc09whcowsdhcwodcydw"}
)
# You can also load the registry from a file. Each line contains a file
# name and it's sha256 hash separated by a space. This makes it easier to
# manage large numbers of data files. The registry file should be packaged
# and distributed with your software.
GOODBOY.load_registry(
    pkg_resources.resource_stream("mypackage", "registry.txt")
)

# Define functions that your users can call to get back the data in memory
def fetch_gravity_data():
    """
    Load some sample gravity data to use in your docs.
    """
    # Fetch the path to a file in the local storage. If it's not there,
    # we'll download it.
    fname = GOODBOY.fetch("gravity-data.csv")
    # Load it with numpy/pandas/etc
    data = pandas.read_csv(fname)
    return data
```

## Getting involved

🗨️ **Contact us:**
Find out more about how to reach us at
[fatiando.org/contact](https://www.fatiando.org/contact/).

👩🏾‍💻 **Contributing to project development:**
Please read our
[Contributing Guide](https://github.com/fatiando/pooch/blob/main/CONTRIBUTING.md)
to see how you can help and give feedback.

🧑🏾‍🤝‍🧑🏼 **Code of conduct:**
This project is released with a
[Code of Conduct](https://github.com/fatiando/community/blob/main/CODE_OF_CONDUCT.md).
By participating in this project you agree to abide by its terms.

> **Imposter syndrome disclaimer:**
> We want your help. **No, really.** There may be a little voice inside your
> head that is telling you that you're not ready, that you aren't skilled
> enough to contribute. We assure you that the little voice in your head is
> wrong. Most importantly, **there are many valuable ways to contribute besides
> writing code**.
>
> *This disclaimer was adapted from the*
> [MetPy project](https://github.com/Unidata/MetPy).

## License

This is free software: you can redistribute it and/or modify it under the terms
of the **BSD 3-clause License**. A copy of this license is provided in
[`LICENSE.txt`](https://github.com/fatiando/pooch/blob/main/LICENSE.txt).
