Contributing

Hi, thanks for your interest in the project! We welcome pull requests from developers of all skill levels.

Jens H. Nielsen, William H.P Nielsen, Mikhail Astafev and Trevor Morgan are the current maintainers of QCoDeS (aka core developers), along with a group of talented and smart volunteers.

Need help? What we recommend to be used for any kind of help and support is to open a thread in a relevant Discussions page in QCoDeS GitHub. You can also join us on Slack, (Please send an email to qcodes-support@microsoft.com to be invited!).

QCoDeS Community Drivers

The QCoDeS instrument drivers that are not supported by the QCoDeS developers should be pushed to the dedicated repository in GitHub:

https://github.com/QCoDeS/Qcodes_contrib_drivers

These drivers are supported on a best effort basis by the developers of the individual drivers.

Note that, any pull request to the main QCoDeS repository concerning unsupported drivers will not be reviewed and/or merged with the QCoDeS core.

Bugs reports and feature requests

We use github’s issues. Search for existing and closed issues. If your problem is not yet addressed, please open a new issue.

The github GUI will show you a template for bugs. Delete the wrong part and try to follow the template. Writing a good issue helps you in the first place. Bug reports must be accompanied by a reproducible example.

Have an idea about future directions to go with Qcodes? Visions of data-utopia that would take more than a few weeks to add or might change some core ideas in the package? Please use “Ideas” section in the GitHub Discussions. We will pick the long-term or discussion labels.

If somebody is assigned to an issue it means that somebody is working on it.

Clever usage

Figured out a new way to use QCoDeS? Found a package that makes your life better and easier? Got realtime analysis working after struggling with it for days? Write it on the “General” section of GitHub Discussions so we can keep our github more organized.

Development

Setup

  • Clone and register the package for development as described in the README

  • Run tests

  • Ready to hack

Running Tests

We don’t want to reinvent the wheel, and thus use py.test. It’s easy to install:

pip install -r test_requirements.txt

Then to test and view the coverage:

pytest --cov=qcodes --cov-report xml --cov-config=setup.cfg

To test and see the coverage (with missing lines) of a single module:

pytest --cov=qcodes.module.submodule --cov-report=term-missing qcodes/tests/test_file.py

You can also run single tests with something like:

pytest.exe .\qcodes\tests\test_config.py
# or
pytest.exe .\qcodes\tests\test_config.py::test_add_and_describe

If the tests pass, you should be ready to start developing!

New code and testing

  • Fork the repo into your github account

  • Make a branch within this repo

  • It is worth considering a good branch name:

    • for example selecting a prefix can be useful:

      • feature/bar (if you add the feature bar)

      • hotfix/bar (if you fix the bug bar)

      • foo/bar (if you foo the bar)

    • never use your username If you can’t figure out a name for your branch, re-think about what you would be doing. It’s always a good exercise to model the problem before you try to solve it. Also, use GitHub Discussions for getting help. We <3 you in the first place.

A note on committing and pushing (if you are not really familiar with git).

A good commit is really important (for you writing it in the first place). If you need a loving guide all the time you commit, see here. Do not push! Unless you are sure about your commits. If you have a typo in your commit message, do not push. If you added more files/changes that the commit says, do not push. In general everything is fixable if you don’t push. The reason is that on your local machine you can always re-write history and make everything look nice, once pushed is just harder to go back. If in doubt, ask and help will be given. Nobody was born familiar with git, and everybody makes mistakes.

  • Write your new feature or fix. Be sure it doesn’t break any existing tests, and please write tests that cover your feature as well, or if you are fixing a bug, write a test that would have failed before your fix. Our goal is 100% test coverage, and although we are not there, we should always strive to increase our coverage with each new feature. Please be aware also that 100% test coverage does NOT necessarily mean 100% logic coverage. If (as is often the case in Python) a single line of code can behave differently for different inputs, coverage in itself will not ensure that this is tested.

  • Write the docs, following the other documentation files (.rst) in the repo as an example. Or write the docs in the form of example IPython notebook (there are many of those in our docs as well).

  • We should have a few high-level “integration” tests, but simple unit tests (that just depend on code in one module) are more valuable for several reasons:

  • If complex tests fail it’s more difficult to tell why

  • When features change it is likely that more tests will need to change

  • Unit tests can cover many scenarios much faster than integration tests.

  • If you’re having difficulty making unit tests, first consider whether your code could be restructured to make it less dependent on other modules. Often, however, extra techniques are needed to break down a complex test into simpler ones. We are happy to help with this on Slack. Two ideas that are useful here:

    • Patching, one of the most useful parts of the unittest.mock library. This lets you specify exactly how other functions/objects should behave when they’re called by the code you are testing.

    • Supporting files / data: Lets say you have a test of data acquisition and analysis. You can break that up into an acquisition test and an analysis by saving the intermediate state, namely the data file, in the test directory. Use it to compare to the output of the acquisition test, and as the input for the analysis test.

  • Refer to QCoDeS documentation on how to implement tests for the instrument drivers.

    • We have not yet settled on a framework for testing real hardware. For some tests we use pyvisa-sim but it’s flexibility is limited. Another interesting candidate is pyvisa-mock. So, stay tuned, or post any ideas you have as “Ideas” in GitHub Discussions!

Coding Style

  • Try to make your code self-documenting. Python is generally quite amenable to that, but some things that can help are:

  • Use clearly-named variables

  • Only use “one-liners” like list comprehensions if they really fit on one line.

  • Comments should be for describing why you are doing something. If you feel you need a comment to explain what you are doing, the code could probably be rewritten more clearly.

  • If you do need a multiline statement, use implicit continuation (inside parentheses or brackets) and implicit string literal concatenation rather than backslash continuation

  • Format non-trivial comments using your GitHub nick and one of these prefixes:

    • TODO( theBrain ): Take over the world!

    • NOTE( pinky ): Well, that’s a good idea.

  • Docstrings are required for modules, classes, attributes, methods, and functions (if public i.e no leading underscore). Because docstrings (and comments) are not code, pay special attention to them when modifying code: an incorrect comment or docstring is worse than none at all! Docstrings should utilize the google style in order to make them read well, regardless of whether they are viewed through help() or on Read the Docs. See the falcon framework for best practices examples.

  • Use PEP8 style. Not only is this style good for readability in an absolute sense, but consistent styling helps us all read each other’s code.

  • There is a command-line tool (pip install pycodestyle) you can run after writing code to validate its style.

  • A lot of editors have plugins that will check this for you automatically as you type. Sublime Text for example has sublimelinter-pep8 and the even more powerful sublimelinter-flake8. For Emacs, the elpy package is strongly recommended (https://github.com/jorgenschaefer/elpy).

  • BUT: do not change someone else’s code to make it pep8-compliant unless that code is fully tested.

  • BUT: remove all trailing spaces.

  • BUT: do not mix tabs and indentation for any reason.

  • JavaScript: The Airbnb style guide is quite good. If we start writing a lot more JavaScript we can go into more detail.

Pull requests

  • Push your branch back to github and make a pull request (PR). If you visit the repo home page soon after pushing to a branch, github will automatically ask you if you want to make a PR and help you with it.

  • Naming matters; try to come up with a nice header:

    • fix(dataformatter): Decouple foo from bar

    • feature: Add logviewer

  • The template will help you write nice pull requests <3 !

  • Try to keep PRs small and focused on a single task. Frequent small PRs are much easier to review, and easier for others to work around, than large ones that touch the whole code base.

  • tag AT LEAST ONE person in the description of the PR (a tag is @username) who you would like to have look at your work. Of course everyone is welcome and encouraged to chime in.

  • It’s OK (in fact encouraged) to open a pull request when you still have some work to do. Just make a checklist (- [ ] take over the world) to let others know what more to expect in the near future.

  • Delete your branch once you have merged (using the helpful button provided by github after the merge) to keep the repository clean. Then on your own computer, after you merge and pull the merged master down, you can call git branch --merged to list branches that can be safely deleted, then git branch -d <branch-name> to delete it.

Automatic Testing (CI)

Once your pull request is opened a number of automatic jobs are created. These will run the tests and in other ways verify the correctness of the code. In the following we will describe what we test and provide a few tips on how to understand the results especially if something should fail.

Note that the some of the automatic jobs are labeled with Required. These must pass before the pull request can be merged. The other jobs that do not have a required label may be considered guidelines. Please attempt to make these pass if possible but feel free to disregard them if the suggested changes do not make sense. If in doubt feel free to ask questions.

Required checks

Our required checks consists of a number of jobs that performs the following actions using multiple python versions, on Linux and on Windows.

  • Run our test suite using pytest as described above.

  • Perform type checking of the code in QCoDeS using MyPy. For many of the modules we enforce that the code must be type annotated. We encourage all contributors to type annotate any contribution to QCoDeS. If you need help with this please feel free to reach out.

  • Build the documentation using Sphinx with Sphinx warnings as errors. This includes execution of all example notebooks that are not explicitly marked as not to be executed. Please see here for information on how to disable execution of a notebook.

  • A number of smaller static checks implemented using pre-commit hooks. You may want to consider installing the pre-commit hooks in your local git config to have these checks performed automatically when you commit.

    • Check that YAML, JSON and Python files are syntactically valid.

    • Check that there are no trailing whitespace or blank lines at the end of python files.

    • Check that all files uses the correct line endings (\n for all files except .bat)

    • Run pyupgrade on all python files.

    • Run Darker. This will enforce Black formatting and sorting of imports using isort on all new and changed code. We do not format the entire codebase to not lose change history.

Furthermore we also run our test suite with the minimum requirements stated to ensure that QCoDeS does work correctly with these.

Optional checks

In addition to the required checks we perform two optional checks that can be regarded as guidelines rather than requirements.

  • We use Codacy to perform a number of style checks using Pylint and Pydocstyle among others. Please adapt your changes to these recommendations as you see fit. It is not a requirement that all Codacy warnings and errors are fixed. Do not insert comments to disable these warnings.

  • We measure code coverage using Codecov. This measures if a line of code is executed as part of a test. As much as possible we would encourage you to add tests to cover all changes. However, this may not always be possible especially when writing instrument drivers.

Documenting QCoDeS

All user facing modules should be included in the QCoDeS api documentation on the QCoDeS homepage.

The documentation is generated by the .rst files in docs\api folder. If you create a new user facing module you should take care to include it here.

For each folder of code there should be a matching folder in the docs\api folder containing an index.rst file and a X.rst file for each of the X.py files that are to be documented. For instance assume that you want to document qcodes.mymodule.a where mymodule is a folder containing an __init__.py and an a.py file. Then the mymodule folder within the api folder should contain an index.rst file and a a.rst file.

The index.rst file should then look like this:

.. _mymodule :

qcodes.mymodule
===============

.. autosummary::

    qcodes.mymodule
    qcodes.mymodule.a


.. automodule:: qcodes.mymodule


.. toctree::
   :maxdepth: 4
   :hidden:

   a

This rst files will generate a page with the title qcodes.mymodule.

The autosummary section generates a linked table with the entries given. The automodule section generates the documentation for mymodule taken from the __init__.py file and the toctree section includes the doc pages of the submodules that should be documented.

The submodule a.py is documented in its own file (a.rst) containing:

qcodes.mymodule.a
-----------------

.. automodule:: qcodes.mymodule.a
   :members:

This automatically generates a page with the documentation of the module a.py

Finally the index.rst file should be included in the toctree in docs/api/index.rst