Developer overview

  1. If you are a first-time contributor:

    • Go to and click the “fork” button to create your own copy of the project.

    • Clone the project to your local computer:

      git clone
    • Add the upstream repository:

      git remote add upstream
    • Now, you have remote repositories named:

      • upstream, which refers to the networkx repository

      • origin, which refers to your personal fork

  2. Develop your contribution:

    • Pull the latest changes from upstream:

      git checkout master
      git pull upstream master
    • Create a branch for the feature you want to work on. Since the branch name will appear in the merge message, use a sensible name such as ‘bugfix-for-issue-1480’:

      git checkout -b bugfix-for-issue-1480
    • Commit locally as you progress (git add and git commit)

  3. To submit your contribution:

    • Push your changes back to your fork on GitHub:

      git push origin bugfix-for-issue-1480
    • Go to GitHub. The new branch will show up with a green Pull Request button—click it.

    • If you want, post on the mailing list to explain your changes or to ask for review.

For a more detailed discussion, read these detailed documents on how to use Git with networkx (

  1. Review process:

    • Reviewers (the other developers and interested community members) will write inline and/or general comments on your Pull Request (PR) to help you improve its implementation, documentation, and style. Every single developer working on the project has their code reviewed, and we’ve come to see it as friendly conversation from which we all learn and the overall code quality benefits. Therefore, please don’t let the review discourage you from contributing: its only aim is to improve the quality of project, not to criticize (we are, after all, very grateful for the time you’re donating!).

    • To update your pull request, make your changes on your local repository and commit. As soon as those changes are pushed up (to the same branch as before) the pull request will update automatically.

    • Travis-CI, a continuous integration service, is triggered after each Pull Request update to build the code and run unit tests of your branch. The Travis tests must pass before your PR can be merged. If Travis fails, you can find out why by clicking on the “failed” icon (red cross) and inspecting the build and test log.

    • AppVeyor, is another continuous integration service, which we use. You will also need to make sure that the AppVeyor tests pass.


If closing a bug, also add “Fixes #1480” where 1480 is the issue number.

Divergence between upstream master and your feature branch

Never merge the main branch into yours. If GitHub indicates that the branch of your Pull Request can no longer be merged automatically, rebase onto master:

git checkout master
git pull upstream master
git checkout bugfix-for-issue-1480
git rebase master

If any conflicts occur, fix the according files and continue:

git add conflict-file1 conflict-file2
git rebase --continue

However, you should only rebase your own branches and must generally not rebase any branch which you collaborate on with someone else.

Finally, you must push your rebased branch:

git push --force origin bugfix-for-issue-1480

(If you are curious, here’s a further discussion on the dangers of rebasing. Also see this LWN article.)

Build environment setup

Once you’ve cloned your fork of the networkx repository, you should set up a Python development environment tailored for networkx. You may choose the environment manager of your choice. Here we provide instructions for two popular environment managers: venv (pip based) and conda (Anaconda or Miniconda).


When using venv, you may find the following bash commands useful:

# Create a virtualenv named ``networkx-dev`` that lives in the directory of
# the same name
python -m venv networkx-dev
# Activate it
source networkx-dev/bin/activate
# Install all development and runtime dependencies of networkx
pip install -r <(cat requirements/*.txt)
# Build and install networkx from source
pip install -e .
# Test your installation
PYTHONPATH=. pytest networkx


When using conda, you may find the following bash commands useful:

# Create a conda environment named ``networkx-dev``
conda create --name networkx-dev
# Activate it
conda activate networkx-dev
# Install major development and runtime dependencies of networkx
# (the rest can be installed from conda-forge or pip, if needed)
conda install `for i in requirements/{default,test,doc,extras}.txt; do echo -n " --file $i "; done`
# Install minimal testing dependencies
conda install pytest
# Install networkx from source
pip install -e . --no-deps
# Test your installation
PYTHONPATH=. pytest networkx


  • All code should have tests.

  • All code should be documented, to the same standard as NumPy and SciPy.

  • All changes are reviewed. Ask on the mailing list if you get no response to your pull request.

Stylistic Guidelines

  • Set up your editor to remove trailing whitespace. Follow PEP08. Check code with pyflakes / flake8.

  • Use the following import conventions:

    import numpy as np
    import scipy as sp
    import matplotlib as mpl
    import matplotlib.pyplot as plt
    import networkx as nx
    cimport numpy as cnp # in Cython code


networkx has an extensive test suite that ensures correct execution on your system. The test suite has to pass before a pull request can be merged, and tests should be added to cover any modifications to the code base.

We make use of the pytest testing framework, with tests located in the various networkx/submodule/tests folders.

To use pytest, ensure that the library is installed in development mode:

$ pip install -e .

Now, run all tests using:

$ PYTHONPATH=. pytest networkx

Or the tests for a specific submodule:

$ PYTHONPATH=. pytest networkx/readwrite

Or tests from a specific file:

$ PYTHONPATH=. pytest networkx/readwrite/tests/

Or a single test within that file:

$ PYTHONPATH=. pytest networkx/readwrite/tests/

Use --doctest-modules to run doctests. For example, run all tests and all doctests using:

$ PYTHONPATH=. pytest --doctest-modules networkx

Test coverage

Tests for a module should ideally cover all code in that module, i.e., statement coverage should be at 100%.

To measure the test coverage, install pytest-cov (using pip install pytest-cov) and then run:

$ PYTHONPATH=. pytest --cov=networkx networkx

This will print a report with one line for each file in networkx, detailing the test coverage:

Name                                             Stmts   Miss Branch BrPart  Cover
networkx/                                33      2      2      1    91%
networkx/algorithms/                    114      0      0      0   100%
networkx/algorithms/approximation/       12      0      0      0   100%
networkx/algorithms/approximation/         42      1     18      1    97%

Pull request codes

When you submit a pull request to GitHub, GitHub will ask you for a summary. If your code is not ready to merge, but you want to get feedback, please consider using WIP: experimental optimization or similar for the title of your pull request. That way we will all know that it’s not yet ready to merge and that you may be interested in more fundamental comments about design.

When you think the pull request is ready to merge, change the title (using the Edit button) to remove the WIP:.

Developer Notes

For additional information about contributing to NetworkX, please see the Developer Notes.