Developer’s Guide

Welcome to the rever developer’s guide! This is a place for developers to place information that does not belong in the user’s guide or the library reference but is useful or necessary for the next people that come along to develop rever.


All code changes must go through the pull request review procedure.


Pull requests will often have CHANGELOG entries associated with. However, to avoid excessive merge conflicts, please follow the following procedure:

  1. Go into the news/ directory,

  2. Copy the TEMPLATE.rst file to another file in the news/ directory. We suggest using the branchname:

    $ cp TEMPLATE.rst branch.rst
  3. Add your entries as a bullet pointed lists in your branch.rst file in the appropriate category. It is OK to leave the None entries for later use.

  4. Commit your branch.rst.

Feel free to update this file whenever you want! Please don’t use someone else’s file name. All of the files in this news/ directory will be merged automatically at release time. The None entries will be automatically filtered out too!

Style Guide

rever is a pure Python project, and so we use PEP8 (with some additions) to ensure consistency throughout the code base.

Rules to Write By

It is important to refer to things and concepts by their most specific name. When writing rever code or documentation please use technical terms appropriately. The following rules help provide needed clarity.


  • User-facing APIs should be as generic and robust as possible.

  • Tests belong in the top-level tests directory.

  • Documentation belongs in the top-level docs directory.


  • Code must have associated tests and adequate documentation.

  • User-interaction code (such as the Shell class) is hard to test. Mechanism to test such constructs should be developed over time.

  • Have extreme empathy for your users.

  • Be selfish. Since you will be writing tests you will be your first user.

Python Style Guide

rever uses PEP8 for all Python code. The following rules apply where PEP8 is open to interpretation.

  • Use absolute imports (import rather than explicit relative imports (import .tools). Implicit relative imports (import tools) are never allowed.

  • Use 'single quotes' for string literals, and """triple double quotes""" for docstrings. Double quotes are allowed to prevent single quote escaping, e.g. "Y'all c'mon o'er here!"

  • We use sphinx with the numpydoc extension to autogenerate API documentation. Follow the numpydoc standard for docstrings.

  • Simple functions should have simple docstrings.

  • Lines should be at most 80 characters long. The 72 and 79 character recommendations from PEP8 are not required here.

  • All Python code should be compliant with Python 3.4+. At some unforeseen date in the future, Python 2.7 support may be supported.

  • Tests should be written with pytest using a procedural style. Do not use unittest directly or write tests in an object-oriented style.

  • Test generators make more dots and the dots must flow!

You can easily check for style issues, including some outright bugs such as mispelled variable names, using pylint. If you’re using Anaconda you’ll need to run “conda install pylint” once. You can easily run pylint on the edited files in your uncommited git change:

$ pylint $(git status -s | awk '/\.py$$/ { print $$2 }' | sort)

If you want to lint the entire code base run:

$ pylint $(find tests rever -name \*.py | sort)

How to Test


Prep your environment for running the tests:

$ pip install -r requirements-tests.txt

Running the Tests - Basic

Run all the tests using pytest:

$ py.test -q

Use “-q” to keep pytest from outputting a bunch of info for every test.

Running the Tests - Advanced

To perform all unit tests:

$ py.test

If you want to run specific tests you can specify the test names to execute. For example to run test_aliases:

$ py.test

Note that you can pass multiple test names in the above examples:

$ py.test

Writing the Tests - Advanced

(refer to pytest documentation)

With the Pytest framework you can use bare assert statements on anything you’re trying to test, note that the name of the test function has to be prefixed with test_:

def test_whatever():
    assert is_true_or_false

The in tests directory defines fixtures for mocking various parts of rever for more test isolation. For a list of the various fixtures:

$ py.test --fixtures

when writing tests it’s best to use pytest features i.e parametrization:

@pytest.mark.parametrize('env', [test_env1, test_env2])
def test_one(env, rever_builtins):
    rever_builtins.__rever_env__ = env

this will run the test two times each time with the respective test_env. This can be done with a for loop too but the test will run only once for the different test cases and you get less isolation.

With that in mind, each test should have the least assert statements, preferably one.

At the moment, rever doesn’t support any pytest plugins.

Happy Testing!

How to Document

Documentation takes many forms. This will guide you through the steps of successful documentation.


No matter what language you are writing in, you should always have documentation strings along with you code. This is so important that it is part of the style guide. When writing in Python, your docstrings should be in reStructured Text using the numpydoc format.

Auto-Documentation Hooks

The docstrings that you have written will automatically be connected to the website, once the appropriate hooks have been setup. At this stage, all documentation lives within rever’s top-level docs directory. We uses the sphinx tool to manage and generate the documentation, which you can learn about from the sphinx website. If you want to generate the documentation, first rever itself must be installed and then you may run the following command from the docs dir:

~/rever/docs $ make html

For each new module, you will have to supply the appropriate hooks. This should be done the first time that the module appears in a pull request. From here, call the new module mymod. The following explains how to add hooks.

Python Hooks

Python documentation lives in the docs/api directory. First, create a file in this directory that represents the new module called mymod.rst. The docs/api directory matches the structure of the rever/ directory. So if your module is in a sub-package, you’ll need to go into the sub-package’s directory before creating mymod.rst. The contents of this file should be as follows:


.. _rever_mymod:

My Awesome Module -- :mod:`rever.mymod`

.. currentmodule:: rever.mymod

.. automodule:: rever.mymod

This will discover all of the docstrings in mymod and create the appropriate webpage. Now, you need to hook this page up to the rest of the website.

Go into the index.rst file in docs/rever or other subdirectory and add mymod to the appropriate toctree (which stands for table-of-contents tree). Note that every sub-package has its own index.rst file.

Building the Website

Building the website/documentation requires the following dependencies:

  1. Sphinx

  2. Cloud Sphinx Theme

Procedure for modifying the website

The rever website source files are located in the docs directory. A developer first makes necessary changes, then rebuilds the website locally by executing the command:

$ make html

This will generate html files for the website in the _build/html/ folder. The developer may view the local changes by opening these files with their favorite browser, e.g.:

$ google-chrome _build/html/index.html

Once the developer is satisfied with the changes, the changes should be committed and pull-requested per usual. Once the pull request is accepted, the developer can push their local changes directly to the website by:

$ make push-root

Branches and Releases

Mainline rever development occurs on the master branch. Other branches may be used for feature development (topical branches) or to represent past and upcoming releases.

Document History

Portions of this page have been forked from the PyNE and Xonsh documentation, Copyright 2015-2016, the xonsh developers. All rights reserved. Copyright 2011-2015, the PyNE Development Team. All rights reserved.