Style Guide

Code formatting

Please run invoke format to auto-format your code.

The command invoke lint runs the entire codebase through both black and flake8. As described in the docs, flake8 includes lint checks provided by the PyFlakes project, PEP-0008 inspired style checks provided by the PyCodeStyle project, and McCabe complexity checking provided by the McCabe project.

The list of potential error codes issued by flake8 are available here:

The PEP-0008 style guide is available here:

Note that the maximum line length is set to 120 rather 79 in the setup.cfg of the repo.

Naming conventions

We (intend to) use the following naming conventions.

  1. variables, functions, methods, attributes use “snake_case”: they are written in lowercase and spaces between words are replaced by underscores.

  2. class names use (Upper) “CamelCase”: The are written in lowercase, with the first letter of each word capitalized and spaces between words removed.

  3. module or package level variables are in uppercase and with spaces between words replaced by underscores.


Ideally, we would use the following conventions for quotes.

  1. Double quotation marks for multiline statements and docstrings. For example, """Calculate the sum of two numbers."""

  2. Single quotation marks for strings that are used “as variables”. For example, config['param'] = 1.

  3. Double quotation marks for strings that are meant to be used as text. For examples, message = "Select one or more points."


The documentation of COMPAS is generated with Sphinx. This means that code docstrings and general documentation pages have to be written in RestructuredText.

Each function, method, and class should have a docstring describing its behaviour. We use sphinx.ext.napoleon to allow for human-readable docstrings, and prefer Numpy-style docstring formatting rules.

To include a new function or class in the documentation, it should be added to the API docstring in of the main package it belongs to.

For example, if you add a function somewhere in the geometry package, make sure to include it in the docstring of

Type hints

Code structure

Each of the core packages is divided into subpackages that group functionality into logical components. For example, compas is divided into:

  • compas.artists


  • compas.datastructures

  • compas.files

  • compas.geometry

  • compas.numerical

  • compas.robots

  • compas.rpc

  • compas.topology

  • compas.utilities

The API of each subpackage is documented in the docstring of its file using basic RestructuredText. From outside of these packages, functionality should be imported directly from the subpackage level, regardless of the code structure underneath.

For example, in some

from compas.datastructures import Mesh
from compas.datastructures import Network

from compas.geometry import add_vectors
from compas.geometry import oriented_bounding_box_numpy
from compas.geometry import Polygon
from compas.geometry import Transformation

from compas.numerical import pca_numpy
from compas.numerical import fd_numpy