Working with Matplotlib in Virtual environments

Contents

• Working with Matplotlib in Virtual environments
  • Introduction
  • GUI Frameworks

Introduction

When running matplotlib in a virtual environment you may discover a few issues. matplotlib itself has no issue with virtual environments. However, the GUI frameworks that matplotlib uses for interactive figures have some issues with virtual environments. Everything below assumes some familiarity with the Matplotlib backends as found in What is a backend?.

If you only use the IPython/Jupyter Notebook‘s inline and notebook backends and non interactive backends you should not have any issues and can ignore everything below.

If you are using Matplotlib on OSX you may also want to consider the OSX framework FAQ.

GUI Frameworks

Interactive Matplotlib relies heavily on the interaction with external GUI frameworks.

Most GUI frameworks are not pip installable. This makes it tricky to install them within a virtual environment. This problem does not exist if you use Conda environments where you can install all Conda supported GUI frameworks directly into the environment. In regular virtualenv environment various workarounds exist. Some of these are given here:

• The TKAgg backend doesn’t require any external dependencies and is normally always available.
• The QT4 framework PySide is pip installable.
• PYQT5 is pip installable on Python 3.5.

Other frameworks are harder to install into a virtual environment. There are at least two possible ways to get access to these in a virtual environment.

One often suggested solution is to use the --system-site-packages option to virtualenv when creating an environment. This adds all system wide packages to the virtual environment. However, this breaks the isolation between the virtual environment and the system install. Among other issues it results in hard to debug problems with system packages shadowing the environment packages. If you use virtualenvwrapper this can be toggled with the toggleglobalsitepackages command.

Alternatively, you can manually symlink the GUI frameworks into the environment. I.e. to use PyQt5, you should symlink PyQt5 and sip from your system site packages directory into the environment taking care that the environment and the systemwide install use the same python version.