This description of Tax-Calculator coding style is written for a person who wants to contribute changes to Tax-Calculator source code. It assumes that you have read the Contributor Guide, have cloned the central GitHub Tax-Calculator repository to your GitHub account and to your local computer, and are familiar with how to prepare a pull request for consideration by the core development team. This document describes the coding style you should follow when preparing a pull request on your local computer. By coding style we mean primarily the vertical and horizontal spacing of the code and the naming of new variables.
You main objective is to write Python code that is indistinguishable in style from existing code in the repository. In other words, after your new code is merged with existing code it should be difficult for somebody else to determine what you contributed.
In order to achieve this objective any new policy parameter names must comply with the parameter naming and placement conventions.
In addition, any new or revised code must meet certain coding style guidelines.
There are two recommended tools that can help you develop seamless and correct code enhancements.
One of these tools, pycodestyle, enforces coding styles that are required
of all Python code in the repository, and therefore, all pull requests
are tested using the pycodestyle tool. Pull requests that fail these
tests need to be revised before they can be merged into the
repository. The most efficient way to comply with this coding style
requirement is to process each file containing revisions through
pycodestyle on your local computer before submitting your pull request.
Make sure you have an up-to-date version of pycodestyle installed on your
computer by entering at the operating system command line:
pycodestyle --version
If you get a no-such-command error, install pycodestyle as follows:
conda install pycodestyle
If you do have pycodestyle installed, but the version is before 2.4.0,
then get a more recent version as follows:
conda update pycodestyle
Once you have a current version of pycodestyle installed on your computer,
use the pycodestyle tool as follows:
pycodestyle records.py
where in the above example you want to check the coding style of your
proposed revisions to the records.py file.
In addition, if you are proposing revisions to one of the files in the
taxcalc directory that has a .json extension, you should use the
pycodestyle tool as follows:
pycodestyle --ignore=E501,E121 current_law_policy.json
where in the above example you want to check the coding style of your
proposed revisions to the current_law_policy.json file.
Note that you can easily check all the Python files in the
directory tree beginning with the taxcalc directory as follows:
cd taxcalc
pycodestyle .
or
pycodestyle taxcalc
The other of these tools, pylint, warns about deviations from a
broader set coding styles than does pycodestyle. The use of pylint,
while being the number one recommendation in the Google Python Style
Guide, is
strictly-speaking optional for Tax-Calculator work. But several
important files in the repository are maintained in a way that their
coding style does not generate any pylint warnings. You can
determine which files these are by looking for the comment near the
top of the file that begins # CODING-STYLE CHECKS:. It is
recommended that, if you are proposing changes in one these files, you
check your work by running the pylint command listed in that file's
coding-style comment.
Make sure you have an up-to-date version of pylint installed on your
computer by entering at the operating system command line:
pylint --version
If you get a no-such-command error, install pylint as follows:
conda install pylint
If you do have pylint installed, but the version is before 1.8.4,
then get a more recent version as follows:
conda update pylint