Django, Poetry, ER Diagrams, Apple MacOS Installation challenges

The goal of this article is to document how to install graphviz so I can easily generate ER diagrams in Django.

django-extensions has a great utility function called Graph models. This will use graphvizto provide a graphical overview or ER diagram of your data models (e.g. an Entity-Relationship diagram of your database tables).

Everytime I try to do this in a new project I have problems installing the supporting library pygraphviz to support this on my Mac (M1+). I’m writing this mostly to make sure I document how to install pygraphviz for myself. Hopefully, it’s helpful to other people as well.

The wonderful people answering the support request for pygraphviz, in particular michaeloliverx and jeanclaude-jardim-oxb, provided easy solutions if you are getting the following error when trying to install pygraphviz:

fatal error: 'graphviz/cgraph.h' file not found

The solution if you are using poetry is the following:

brew install graphviz

export CFLAGS="-I $(brew --prefix graphviz)/include"
export LDFLAGS="-L $(brew --prefix graphviz)/lib"
poetry add pygraphviz

and the solution if you are using pip is the following:

python3 -m pip install \
                --config-settings="--global-option=build_ext" \
                --config-settings="--global-option=-I$(brew --prefix graphviz)/include/" \
                --config-settings="--global-option=-L$(brew --prefix graphviz)/lib/" \
                pygraphviz

After this, and of course installing django-extensions, you can run:

./manage.py graph_models -a -g -o db_visualized.png

to get something like this: