Visualizing the DAG

To visualize the DAG of the project, first, install pygraphviz and graphviz. For example, you can both install with conda

$ conda install -c conda-forge pygraphviz

After that, pytask offers two interfaces to visualize your project’s DAG.

Command-line interface

You can quickly create a visualization with this command.

$ pytask dag

It generates a dag.pdf in the current working directory.

If you do not want to generate a PDF, use pytask dag --output-path or, shorter, pytask dag -o to choose a different format inferred from the file-ending. Select any format supported by graphviz.

$ pytask dag -o dag.png

You can change the graph’s layout by using the pytask dag --layout option. Its default is set to dot and produces a hierarchical structure. graphviz supports other layouts, which are listed here.

Programmatic Interface

The programmatic and interactive interface allows customizing the figure.

Similar to pytask.main(), there exists pytask.build_dag() which returns the DAG as a networkx.DiGraph.

@pytask.mark.produces(BLD / "dag.svg")
def task_draw_dag(produces):
    dag = pytask.build_dag({"paths": SRC})

Customization works best on the networkx.DiGraph. For example, here, we set the shape of all nodes to hexagons by adding the property to the node attributes.

nx.set_node_attributes(dag, "hexagon", "shape")

For drawing, you better switch to pygraphviz since the matplotlib backend handles shapes with texts poorly. Here we store the graph as a .svg.

graph = nx.nx_agraph.to_agraph(dag)
graph.draw(path, prog=layout)