Building a Python Project

What This Guide Covers

This guide covers build environment and configuration topics specific to Python projects. Please make sure to read our Getting Started and general build configuration guides first.

Python builds are not available on the OS X environment.

Choosing Python versions to test against

Travis CI supports Python versions 2.6, 2.7, 3.2, 3.3, 3.4, 3.5, 3.6 as well as recent development versions.

language: python
  - "2.6"
  - "2.7"
  - "3.2"
  - "3.3"
  - "3.4"
  - "3.5"
  - "3.5-dev" # 3.5 development branch
  - "3.6"
  - "3.6-dev" # 3.6 development branch
  - "3.7-dev" # 3.7 development branch
  - "nightly" # currently points to 3.7-dev
# command to install dependencies
install: "pip install -r requirements.txt"
# command to run tests
script: pytest

As time goes, new releases come out and we provision more Python versions and/or implementations, aliases like 3.2 will float and point to different exact versions, patch levels and so on.

For precise versions pre-installed on the VM, please consult “Build system information” in the build log.

Travis CI Uses Isolated virtualenvs

CI Environment uses separate virtualenv instances for each Python version. System Python is not used and should not be relied on. If you need to install Python packages, do it via pip and not apt.

If you decide to use apt anyway, note that Python system packages only include Python 2.7 libraries on Ubuntu 12.04 LTS. This means that the packages installed from the repositories are not available in other virtualenvs even if you use the –system-site-packages option.

PyPy Support

Travis CI supports PyPy and PyPy3.

To test your project against PyPy, add “pypy” or “pypy3” to the list of Pythons in your .travis.yml:

language: python
  - "2.6"
  - "2.7"
  - "3.2"
  - "3.3"
  - "3.4"
  # PyPy versions
  - "pypy"  # PyPy2 2.5.0
  - "pypy3" # Pypy3 2.4.0
  - "pypy-5.3.1"
# command to install dependencies
  - pip install .
  - pip install -r requirements.txt
# command to run tests
script: pytest

Default Python Version

If you leave the python key out of your .travis.yml, Travis CI will use Python 2.7.

Specifying Test Script

Python projects need to provide the script key in their .travis.yml to specify what command to run tests with.

For example, if your project uses pytest:

# command to run tests
script: pytest  # or py.test for Python versions 3.5 and below

if it uses make test instead:

script: make test

If you do not provide a script key in a Python project, Travis CI prints a message and fails the build.

Dependency Management


By default Travis CI uses pip to manage python dependencies. If you have a requirements.txt file, Travis CI runs pip install -r requirements.txt during the install phase of the build.

You can manually override this default install phase, for example:

install: pip install --user -r requirements.txt

Custom Dependency Management

To override the default pip dependency management, alter the before_install step as described in general build configuration guide.

Pre-installed packages

Travis CI installs the following packages by default in each virtualenv:

  • pytest
  • nose
  • mock

Testing Against Multiple Versions of Dependencies (e.g. Django or Flask)

If you need to test against multiple versions of, say, Django, you can instruct Travis CI to do multiple runs with different sets or values of environment variables. Use env key in your .travis.yml file, for example:


and then use ENV variable values in your dependencies installation scripts, test cases or test script parameter values. Here we use ENV variable value to instruct pip to install an exact version:

  - pip install -q Django==$DJANGO_VERSION
  - python -q install

The same technique is often used to test projects against multiple databases and so on. For a real world example, see getsentry/sentry and jpvanhal/flask-split.

Nightly build support

Travis CI supports a special version name nightly, which points to a recent development version of CPython build.

It also has the packages above pre-installed.

On-demand installations

For a limited number of Python development releases, on-demand installation is available.

Currently, these are: 3.5-dev (built nightly), 3.5/3.5.0.

Build Matrix

For Python projects, env and python can be given as arrays to construct a build matrix.