Using Graphviz

Graphviz is a utility library that helps generate graphs programmatically. There is a graphviz Python binding for the library.

The apk package manager can generate Graphviz graphs of package dependencies. This capability is leveraged during the prerequisite installation and set up for this example.

Install Graphviz

Note:

Open the python_graphviz.md file in the ~/projects/READMEs folder to help to copy and paste commands.

  1. Run the following command to install Graphviz and its related packages:

    sudo apk add graphviz graphviz-dev graphviz-graphs python3-gv

  2. Test the installation by generating dependency graphs for the python3 package:

    cd ~/projects/python_graphviz
sudo apk dot python3 > python3.gv

  3. Generate the dependency graph in PNG format:

    dot -Tpng python3.gv > python3_dot.png

  4. Open the project folder using the File Manager:



  5. Open the graph using using your default image viewer to see it full size:



Prepare to work with Graphviz in Python

The following steps detail the perquisites required to use the Python viewer.

  1. Run the following command to install the Python package:

    pip3 install graphviz --break-system-packages

  2. Edit /home/qnxuser/.local/lib/python3.14/site-packages/graphviz/backend/mixins.py:

    vi /home/qnxuser/.local/lib/python3.14/site-packages/graphviz/backend/mixins.py

  3. Copy the _view_linux static function and add it to the line below. Rename it _view_qnx, then save and quit:

    _view_linux = staticmethod(viewing.view_unixoid)^M
^M
_view_qnx = staticmethod(viewing.view_unixoid)^M
^M
    Note:

    The ^M's are representations of carriage returns in the editor.

  4. Edit /home/qnxuser/.local/lib/python3.14/site-packages/graphviz/backend/viewing.py:

    vi /home/qnxuser/.local/lib/python3.14/site-packages/graphviz/backend/viewing.py

  5. Add a notation for view_unixoid to attach it to qnx, similar to the existing attachment notation for linux. Then, save and quit:

    @_tools.attach(view, 'linux')^M
@_tools.attach(view, 'freebsd')^M
@_tools.attach(view, 'qnx')^M

Run the sample script

Now, open Geany and try a sample script adapted from this resource: https://graphviz.readthedocs.io/en/stable/examples.html.

Note:

Graphviz's default format is PDF but the desktop environment doesn't include a PDF viewer. The following example opens a PNG viewer and exports a PNG file of the graph instead.

  1. In Geany, open /home/qnxuser/projects/python_graphviz/hello_graphviz.py:



  2. Open the Build menu and select Execute. This opens a "Hello, World!" graph in your default image viewer:



    You can also access the graph from the File Manager. Right-click the hello_world.gv.png file and open it with your image viewer:



  3. Open python3_dot.py and execute it to see the dependency graph for the python3 package in your image viewer:



Next steps

You can also try to adapt the sample scripts in Graphviz's "Example" section to run in the environment: https://graphviz.readthedocs.io/en/stable/examples.html.

Note:

Similarly to the example above, you need to adapt the initialization to include setting the format. To do so, create the sample script locally and copy it into the VM with scp. Then, open it from within the desktop environment.

Page updated: