Contributions are welcome, and they are greatly appreciated! Every little bit helps, and credit will always be given.

You can contribute in many ways:

Types of Contributions#

Report Bugs#

Report bugs at

If you are reporting a bug, please include:

  • Any details about your local setup that might be helpful in troubleshooting.

  • Detailed steps to reproduce the bug.

Fix Bugs#

Look through the GitHub issues for bugs. Anything tagged with “bug” is open to whoever wants to implement it.

Implement Features#

Look through the GitHub issues for features. Anything tagged with “feature” is open to whoever wants to implement it.

Write Documentation#

Atmospheric data Community Toolkit could always use more documentation, whether as part of the official Atmospheric data Community Toolkit docs, in docstrings, or even on the web in blog posts, articles, and such.

Submit Feedback#

The best way to send feedback is to file an issue at

If you are proposing a feature:

  • Explain in detail how it would work.

  • Keep the scope as narrow as possible, to make it easier to implement.

  • Remember that this is a volunteer-driven project, and that contributions are welcome :)

Get Started!#

Ready to contribute? Here’s are a few steps we will go over for contributing to act.

  1. Fork the arm-community-toolkit repo on GitHub and clone your fork locally.

  2. Install your local copy into an Anaconda environment. Assuming you have anaconda installed.

  3. Create a branch for local development.

  4. Create or modified code so that it produces doc string and follows standards.

  5. Install your pre-commit <> hooks, by using pre-commit install

  6. Set up environment variables (Optional)

  7. Local unit testing using Pytest.

  8. Commit your changes and push your branch to GitHub and submit a pull request through the GitHub website.

Fork and Cloning the ACT Repository#

To start, you will first fork the arm-community-toolkit repo on GitHub by clicking the fork icon button found on the main page here:

After your fork is created, git clone your fork. I would not clone the main repository link unless your just using the package as an install and not development. The main master is used as a remote for upstream for grabbing changes as others contribute.

To clone and set up an upstream, use:

git clone

or if you have ssh key setup:

git clone

After that, from within the ACT directory, do:

git remote add upstream


The easiest method for using ACT and is dependencies is by using: Anaconda or Miniconda. From within the ACT directory, you can use:

pip install -e .

This downloads ACT in development mode. Do this preferably in a conda environment. For more on Anaconda and environments:

Working with Git Branches#

When contributing to ACT, the changes created should be in a new branch under your forked repository. Let’s say the user is adding a new plot display. Instead of creating that new function in your master branch. Create a new branch called ‘wind_rose_plot’. If everything checks out and the admin accepts the pull request, you can then merge the master branch and wind_rose_plot branch.

To delete a branch both locally and remotely, if done with it:

git push origin --delete <branch_name>
git branch -d <branch_name>

or in this case:

git push origin --delete wind_rose_plot
git branch -d wind_rose_plot

To create a new branch:

git checkout -b <branch_name>

If you have a branch with changes that have not been added to a pull request but you would like to start a new branch with a different task in mind. It is recommended that your new branch is based on your master. First:

git checkout master


git checkout -b <branch_name>

This way, your new branch is not a combination of your other task branch and the new task branch, but is based on the original master branch.

Typing git status will not only inform the user of what files have been modified and untracked, it will also inform the user of which branch they are currently on.

To switch between branches, simply type:

git checkout <branch_name>

Python File Setup#

When adding a new function to ACT, add the function in the for the submodule so it can be included in the documentation.

Following the introduction code, modules are then added. To follow pep8 standards, modules should be added in the order of:

  1. Standard library imports.

  2. Related third party imports.

  3. Local application/library specific imports.

For example:

import glob
import os

import numpy as np
import as ma

from .dataset import ACTAccessor

Following the main function def line, but before the code within it, a doc string is needed to explain arguments, returns, references if needed, and other helpful information. These documentation standards follow the NumPy documentation style.

For more on the NumPy documentation style:

An example:

def read_arm_netcdf(filenames, variables=None):

    Returns `xarray.Dataset` with stored data and metadata from a
    user-defined query of standard netCDF files from a single

    filenames : str or list
        Name of file(s) to read
    variables : list, optional
        List of variable name(s) to read

    act_obj : Object
        ACT dataset

    This example will load the example sounding data used for unit

    .. code-block:: python

        import act

        the_ds, the_flag =

As seen, each argument has what type of object it is, an explanation of what it is, mention of units, and if an argument has a default value, a statement of what that default value is and why.

Private or smaller functions and classes can have a single line explanation.

An example:

def _get_value(self):
    """Gets a value that is used in a public function."""

Code Style#

ACT follows PEP8 coding standards. To make sure your code follows the PEP8 style, you can use a variety of tools that can check for you. Two popular PEP8 check modules are flake8 and pylint. (Note: ACT’s continuous integration uses flake8).

For more on pep8 style:

To install flake8:

conda install -c conda-forge flake8

To use flake8:

flake8 path/to/code/to/

To install pylint:

conda install pylint

To use pylint:

pylint path/to/code/to/

Both of these tools are highly configurable to suit a user’s taste. Refer to the tools documentation for details on this process.

Naming Convenction#


When adding discovery modules or functions please adhere to the following * Filenames should just include the name of the organization (arm) or portal (airnow) and no other filler words like get or download * Functions should follow [get/download]_[org/portal]_[data/other description]. If it is getting data but not downloading a file, it should start with get, like get_asos_data. If it downloads a file, it should start with download. The other description can vary depending on what you are retrieving. Please check out the existing functions for ideas.


Similarly, for the io modules, the names should not have filler and just be the organization or portal name. The functions should clearly indicate what it is doing like read_arm_netcdf instead of read_netcdf if the function is specific to ARM files.

Adding Secrets and Environment Variables#

In some cases, unit tests (as noted in the next section), need some username/password/token information and that is not something that is good to make public. For these instances, it is recommended that users set up environment variables for testing. The following environment variables should be set on the user’s local machine using the user’s own credentials for all tests to run properly.

Atmospheric Radiation Measurement User Facility -



Environmental Protection Agency AirNow -


If adding tests that require new environment variables to be set, please reach out to the ACT development team through the pull request. The ACT development team will need to do the following to ensure it works properly when merged in. Note, due to security purposes these secrets are not available to the actions in a pull request but will be available once merged it.

1.) Add a GitHub Secret to ACT settings that’s the same as that in the test file

2.) Add this name to the “env” area of the GitHub Workflow yml files in .github/workflows/*

3.) If the amount of code will impact the decrease in coverage during testing, update the threshold in coveralls

4.) Upon merge, this should automatically pull in the secrets for the testing but there have been quirks. Ensure that tests run properly

Unit Testing#

When adding a new function to ACT it is important to add your function to the file under the corresponding ACT folder.

Create a test for your function and have assert from numpy testing test the known values to the calculated values. If changes are made in the future to ACT, pytest will use the test created to see if the function is still valid and produces the same values. It works that, it takes known values that are obtained from the function, and when pytest is ran, it takes the test function and reruns the function and compares the results to the original.

An example:

import act
import numpy as np
import xarray as xr

def test_correct_ceil():
    # Make a fake dataset to test with, just an array with 1e-7
    # for half of it.
    fake_data = 10 * np.ones((300, 20))
    fake_data[:, 10:] = -1
    arm_obj = {}
    arm_obj["backscatter"] = xr.DataArray(fake_data)
    arm_obj = act.corrections.ceil.correct_ceil(arm_obj)
    assert np.all(arm_obj["backscatter"].data[:, 10:] == -7)
    assert np.all(arm_obj["backscatter"].data[:, 1:10] == 1)

Pytest is used to run unit tests in ACT.

It is recommended to install ACT in “editable” mode for pytest testing. From within the main ACT directory:

pip install -e .

This lets you change your source code and rerun tests at will.

To install pytest:

conda install -c conda-forge pytest

To run all tests in pyart with pytest from outside the pyart directory:

pytest --pyargs act

All test with increase verbosity:

pytest -v

Just one file:

pytest filename

Note: When an example shows filename as such:

pytest filename

filename is the filename and location, such as:

pytest /home/user/act/act/tests/

Relative paths can also be used:

cd ACT
pytest ./act/tests/

For more on pytest:

Note: When testing ACT, the unit tests will download files from different datastreams as part of the tests. These files will download to the directory from where the tests were ran. These files will need to be added to the .gitignore if they are in a location that isn’t caught by the .gitignore. More on using git can be seen below.

Adding Changes to GitHub#

Once your done updating a file, and want the changes on your remote branch. Simply add it by using:

git add <>

When commiting to GitHub, start the statement with a acronym such as ‘ADD:’ depending on what your commiting, could be ‘MAINT:’ or ‘BUG:’ or more. Then following should be a short statement such as “ADD: Adding new wind rose display.”, but after the short statement, before finishing the quotations, hit enter and in your terminal you can then type a more in depth description on what your commiting.

A set of recommended acronymns can be found at:

If you would like to type your commit in the terminal and skip the default editor:

git commit -m "STY: Removing whitespace from pep8."

To use the default editor(in Linux, usually VIM), simply type:

git commit

One thing to keep in mind is before doing a pull request, update your branches with the original upstream repository.

This could be done by:

git fetch upstream

After fetching, a git merge is needed to pull in the changes.

This is done by:

git merge upstream/master

To prevent a merge commit:

git merge --ff-only upstream/master

or a rebase can be done with:

git pull --rebase upsteam master

Rebase will take commits you missed and stack your changes on top of them.

Before you submit a pull request, check that it meets these guidelines:

  1. The pull request should include tests.

  2. If the pull request adds functionality, the docs should be updated. Put your new functionality into a function with a docstring, and add the feature to the list in README.rst.

  3. The pull request should work for Python 2.7, 3.6, 3.7 for PyPy. Check and make sure that the tests pass for all supported Python versions.

After creating a pull request through GitHub, and outside checker TravisCI will determine if the code past all checks. If the code fails the tests, as the pull request sits, make changes to fix the code and when pushed to GitHub, the pull request will automatically update and TravisCI will automatically rerun.

For more on Git: