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Best Practices

Code Review

All patches that go into a project repo need to be code reviewed by someone other than the original author. Code review is a great way to both learn from others as well as improve code quality. Contribution to code review is highly recommended regardless of activity as a committer.

Below provides a simple checklist of common items that code reviewers should look out for (Patch submitters can use this to self-review as well to ensure that they are not hitting any of these):


  • Does the Git commit message sufficiently describes the change? (Refer to:
  • Does the commit message have an ‘Issue: <someissue>’ in the footer and not in the subject line or body?
  • Are there any typos?
  • Are all code review comments addressed?
  • Is the code rebased onto the latest HEAD of the branch?
  • Does the code pull in any dependencies that might have license conflicts with this project’s license?


  • Are imports alphabetical and sectioned off by stdlib, 3rdparty, and local?
  • Are functions / methods organized alphabetically? (or categorized alphabetically)
  • Does the change need unit tests? (Yes, it probably does!)
  • Does the change need documentation?
  • Does every function added have function docs? (javadoc, pydoc, whatever the language code docs is)
  • Does it pass linting?
  • Does the code cause backwards compatibility breakage? (If so it needs documentation)


Refer to Google’s blog (google-blog-code-health) on effective code review.

Generic Linting (Coala)

Coala is a great tool for linting all languages. The easiest way to run Coala is with python-tox and requires Python 3 installed on the system:

tox -ecoala

Running Coala without Tox can come in handy for executing Coala in interactive mode. In this case, install Coala in a Python viritualenv. Use virtualenvwrapper as it makes it simple to manage local virtual environments.


Install Coala


Some distros have a package called coala available but do not confuse this package with python-coala which is an entirely different piece of software.

Using virtualenv (assuming virtualenvwrapper is available), install Coala:

mkvirtualenv --python=/usr/bin/python3 coala
pip install coala coala-bears
coala --help

For future usage of an existing virtualenv, activate as follows:

# Re-activate Coala virtualenv
workon coala
# Run the coala command
coala --help

Set up Coala for a Project

Use python-tox to manage a Coala setup for any projects that require linting.


Configure the project with a tox.ini and a .coafile file. Below are examples of .coafile and tox.ini as defined by lftools. Inside the tox.ini file the interesting bits are under [testenv:coala].


ignore = .tox/**,

bears = GitCommitBear
ignore_length_regex = Signed-off-by,

bears = WriteGoodLintBear
files = docs/**/*.rst

bears = MarkdownBear,SpaceConsistencyBear,WriteGoodLintBear
files = **.md, **.markdown
use_spaces = true


minversion = 1.6
envlist =

basepython = python3
deps =
commands =
    nodeenv -p
    npm install --global remark-cli remark-lint write-good
    python3 -m nltk.downloader punkt maxent_treebank_pos_tagger averaged_perceptron_tagger
    coala --non-interactive

deps = -rrequirements.txt
commands =
    sphinx-build -W -b html -n -W -d {envtmpdir}/doctrees ./docs/ {toxinidir}/docs/_build/html

deps = -rrequirements.txt
commands = sphinx-build -W -b linkcheck -d {envtmpdir}/doctrees ./docs/ {toxinidir}/docs/_build/linkcheck