Developer Guidelines

Pull Requests

Pull requests should:

  • Conform to existing style in the project
  • Add documentation for new functionality, where applicable
  • Add unit test coverage for new functionality, where applicable
  • Lint the code


This project adheres to just about everything in PEP8, with the exception of line length restrictions and some specifics around indentation.

Line Length

Since the primary mechanism for code submission and review is GitHub, we’re allowed a little more freedom with regard to line length. The GitHub review panel is 100 characters wide, so the max line length for this project is similarly 100 characters.

Block Indentation

PEP8 does account for indentation of multi-line block statements, but only “officially” supports the following:

def a_very_long_function_name_that_takes_a_lot_of_arguments(will, need,
                                                            to, be,
                                                            like, this)


def a_very_long_function_name_that_takes_a_lot_of_arguments(
        will, need, to, be, indented, like, this)

This would normally be disallowed, but can lead to better looking and more compact (but still quite readable) code:

def a_very_long_function_name_that_takes_a_lot_of_arguments(will, need
        to, be, indented, like, this)
    # Note the two indents on the second line of the block statement,
    # which clearly separates the block statement from the trailing
    # code.


Flake8 is an excellent tool for basic code linting to check for adherence to style. It can be installed with pip or easy_install.

An example flake8.conf, reflecting this project’s specific exceptions to PEP8:

ignore = E128
max-line-length = 100


Before posting a release

  • Ensure that tests pass on your local machine, and after pushing ensure that the tests pass in the continuous integration system.
  • Ensure that the sphinx docs can be generated without error (preferably without any warnings, too)
  • Create a source distribution with python sdist. Install that source distribution into a newly created virtualenv (or other “clean” environment), verify that it installs properly
  • Create and tag a release commit, with changes listed. The tagging format is ‘$VERSION’, e.g. ‘0.1.2’, and the list of changes should be in the ChangeLog file (generated by pbr after running python sdist


This project adheres to Semantic Versioning. During the beta period, the x (major) version number is 0, and the y and z versions are intended to represent what the x and y numbers would mean, respectively.

Thus, with the x version set to 0, incrementing the y version signals possible backward-incompatible API changes that will require dependent code changes, while incrementing the z version signals backward-compatible changes, either new functionality in the API, bug fixes, or general improvements.