1.1. Generic Style Guide

1.1.1. General

The content of this website is intended to help new team members understand the direction of our team.

It also helps novice and advance beginners by providing a set of simple rules. Anyone should read this as best practice and provide feedback in case something is wrong.

  • All code in any code-base should look like a single person typed it, no matter how many people contributed.

  • No single person is responsible for a part of the code. We write code together, we take the blame together, we take the glory together. Once a code was approved for review, reviewers are also responsible for that code.

  • Write all code as if it will be written once and read a thousand times. Write code for maximum readability.

  • When you need a trade-off between readability and code duplication, choose to have a code less readable but without duplication.

  • Write code as it will be used by humans, not by a machine. You are not a compiler / interpreter.

  • Don’t use abbreviation. Use full, meaningful names. People with a C background might say that is always OK to use i and j for the iterating, but most of our code is Python so write iterators so that using an index is not needed.

  • Don’t use tabs for indentation, and in general don’t use tabs for anything else. The only exceptions are Makefiles.

  • Favour indentation using 4 spaces. For deep nested languages (HTML, XML) it is OK to use 2 spaces.

  • Maximum line length for code is 80 characters, but for Python we use 79 to be in sync with PEP8 Style Guide for Python Code. In this way, is easier to compare code, even when using a single monitor on a laptop.

  • No need for the ultimate purism, when using / calling code from external libraries it is OK if those calls don’t comply with coding convention.

  • When extending external libraries, use the coding convention used by that library. It might be harder to define the border of those changes but this should help with sending patches upstream.

  • Words are an important part of how software works. Even though there may be dozens of people creating a product, reading comments, documentation, notes etc, it should still sound like we speak in one consistent voice.

  • When writing text for the documentation or text that appears in the program favour classy over cute or mechanical. Respect the reader, act more like a human and less like a computer, and use fewer words:

    Instead of:
    Successfully deleted the #{branch_name} branch.
    Try something like:
    The #{branch_name} branch has been deleted.
  • Write code so that it can be read / used by developers having a work style different than yours. Don’t add IDE / text editor specific things Don’t assume that other developer will use the same IDE / text editor, fancy keyboard (or foot pedals), array of huge monitors…

  • When you have a non-trivial conditional expression (logical condition from an if statement), break it into smaller sub-conditionals.

# Long conditional which is not that bad.
if ((source.length < source.MAX_SIZE) and
    (destination.state != ACTIVE) and
    (destination.state != PAUSED)):

# But can be better.
source_not_full = source.length < source.MAX_SIZE
destination_available = (
    (destination.state != ACTIVE) and
    (destination.state != PAUSED)

if source_not_full && destination_available:

# Or even better.
class Source(object):
  MAX_SIZE = 10
  def not_full(self):
    return self.size < self.MAX_SIZE

class Destination(object):
  ACTIVE = 1
  PAUSED = 2

  def ready(self):
    return (
      (destination.state != self.ACTIVE) and
      (destination.state != self.PAUSED)

if source.not_full and destination.ready:


  • All comments should be valid sentences and should end with a full stop (.). In this way it is easier to see if the information is complete, or that someone forget to complete a sentence.

  • Try to write code so that it speaks for itself, and so that a comment is not required. Comments and code have a bad habit of getting out of sync and this will lead to the confusion as you might not know whether the comment or the code is expected behaviour. To mitigate this, we have test, which have special docstrings.

  • Try to name variables, methods, functions so that they communicate their intent. A comment is only written in the place where the name is defined, and not present in all other multiple places where it is used. IDE can help, but we should not rely on that.

  • When writing a comment is like saying: “I have no idea for a better name for this thing, so here is my poor comment”, good luck with figuring out the intent of this name when you see it in the rest of the file.”

  • Place comments on a new line above their subject and in the same block as the referred code.

if some_condition:
  # We got into into this branch to do x.

for line in lines:
  if line.startswith('marker'):
    # Marker lines are ignored.
  • Avoid end of line comments.

1.1.3. Feature branch development

The code of our project is shared by all members of the team.

We often have a feature branch that is driven by a single developer, but during the branch lifetime or the review process that branch may get contributions from other developers. For example typo-fixes or small GUI fixes.

To reduce conflicts and confusion between colleagues, avoid using git commands that rewrite the history of commits you have already pushed (such as rebase or commit with amend).

See here on how to keep a feature branch up to date. Don’t revert, just push the fix

If a merge into the main branch is breaking something, first consider creating a new branch that should fix the issues.

If the fix will take more than 2 or 3 days to fix, then revert the merge to have a functional main branch. Delete obsolete branches

Branches you no longer need can be a nuisance, both on your machine and on GitHub, by polluting auto-complete and screen space. These can be:

  • Branches that were already merged,

  • Branches for which the code is already in the main branch or another branch, even if the branch itself was not merged, or

  • Obsolete branches on which we will never work in the future.

To delete a local merged branch:

git branch -d <branch_name>

To delete a remote branch, use the Delete branch button in GitHub PR after the branch is merged or, as of Git v1.7.0:

git push -d origin <branch_name>

For more details, see here.