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Contributing to DueCredit

Files organization

  • duecredit/ is the main Python module where major development is happening, with major submodules being:
    • cmdline/ contains commands for the command line interface. See any of the cmd_*.py files here for an example
    • tests/ all unit- and regression- tests
      • provides convenience helpers used by unit-tests such as @with_tree, @serve_path_via_http and other decorators
  • tools/ might contain helper utilities used during development, testing, and benchmarking of DueCredit. Implemented in any most appropriate language (Python, bash, etc.)

How to contribute

The preferred way to contribute to the DueCredit code base is to fork the main repository on GitHub. Here we outline the workflow used by the developers:

  1. Have a clone of our main project repository as origin remote in your git:

       git clone git://
  2. Fork the project repository: click on the 'Fork' button near the top of the page. This creates a copy of the code base under your account on the GitHub server.

  3. Add your forked clone as a remote to the local clone you already have on your local disk:

       git remote add gh-YourLogin
       git fetch gh-YourLogin

    To ease addition of other github repositories as remotes, here is a little bash function/script to add to your ~/.bashrc:

     ghremote () {
             git remote add gh-$login $url
             git fetch gh-$login

    thus you could simply run:


    to add the above gh-YourLogin remote.

  4. Create a branch (generally off the origin/master) to hold your changes:

       git checkout -b nf-my-feature

    and start making changes. Ideally, use a prefix signaling the purpose of the branch

    • nf- for new features
    • bf- for bug fixes
    • rf- for refactoring
    • doc- for documentation contributions (including in the code docstrings). We recommend to not work in the master branch!
  5. Work on this copy on your computer using Git to do the version control. When you're done editing, do:

       git add modified_files
       git commit

    to record your changes in Git. Ideally, prefix your commit messages with the NF, BF, RF, DOC similar to the branch name prefixes, but you could also use TST for commits concerned solely with tests, and BK to signal that the commit causes a breakage (e.g. of tests) at that point. Multiple entries could be listed joined with a + (e.g. rf+doc-). See git log for examples. If a commit closes an existing DueCredit issue, then add to the end of the message (Closes #ISSUE_NUMER)

  6. Push to GitHub with:

       git push -u gh-YourLogin nf-my-feature

    Finally, go to the web page of your fork of the DueCredit repo, and click 'Pull request' (PR) to send your changes to the maintainers for review. This will send an email to the committers. You can commit new changes to this branch and keep pushing to your remote -- github automagically adds them to your previously opened PR.

(If any of the above seems like magic to you, then look up the Git documentation on the web.)

Quality Assurance

It is recommended to check that your contribution complies with the following rules before submitting a pull request:

  • All public methods should have informative docstrings with sample usage presented as doctests when appropriate.

  • All other tests pass when everything is rebuilt from scratch.

  • New code should be accompanied by tests.


All tests are available under duecredit/tests. To execute tests, the codebase needs to be "installed" in order to generate scripts for the entry points. For that, the recommended course of action is to use virtualenv, e.g.

virtualenv --system-site-packages venv-tests
source venv-tests/bin/activate
pip install -e '.[tests]'

On Debian-based systems you might need to install some C-libraries to guarantee installation (building) of some Python modules we use. So for lxml please first

sudo apt-get install libxml2-dev libxslt1-dev

On Mac OS X Yosemite additional steps are required to make lxml work properly (see this stackoverflow answer). We recommend using homebrew to install the same dependencies (see the Homebrew website to install it), then run

brew install libxml2 libxslt
brew link libxml2 --force
brew link libxslt --force

note that this will override the default libraries installed with Mac OS X.

Then use that virtual environment to run the tests, via

python -m py.test -s -v duecredit

or similarly,

py.test -s -v duecredit

then to later deactivate the virtualenv just simply enter



You can also check for common programming errors with the following tools:

  • Code with good unittest coverage (at least 80%), check with:

        pip install pytest coverage
        coverage run --source duecredit -m py.test
        coverage report


We are not (yet) fully PEP8 compliant, so please use these tools as guidelines for your contributions, but not to PEP8 entire code base.

Sidenote: watch Raymond Hettinger - Beyond PEP 8

  • No pyflakes warnings, check with:

         pip install pyflakes
         pyflakes path/to/
  • No PEP8 warnings, check with:

         pip install pep8
         pep8 path/to/
  • AutoPEP8 can help you fix some of the easy redundant errors:

         pip install autopep8
         autopep8 path/to/

Also, some team developers use PyCharm community edition which provides built-in PEP8 checker and handy tools such as smart splits/joins making it easier to maintain code following the PEP8 recommendations. NeuroDebian provides pycharm-community-sloppy package to ease pycharm installation even further.

Easy Issues

A great way to start contributing to DueCredit is to pick an item from the list of Easy issues in the issue tracker. Resolving these issues allows you to start contributing to the project without much prior knowledge. Your assistance in this area will be greatly appreciated by the more experienced developers as it helps free up their time to concentrate on other issues.