@Marvin, is there a way of having prefect produce a DAG of the workflow in code?

Yes, in Prefect 3.x, you can visualize the structure of your workflow as a Directed Acyclic Graph (DAG) using the

visualize()

method on your flow. This method attempts to produce a schematic diagram of the flow and its tasks without executing the flow code. However, note that functions and code outside of flows or tasks will still be run when calling

visualize()

, which may lead to unintended consequences. To avoid this, encapsulate your code within tasks. To use this feature, you need to have Graphviz installed and available on your system's PATH. Simply installing the Graphviz Python package is not enough. You can download Graphviz from here. Keep in mind that Prefect cannot automatically generate a schematic for dynamic workflows, such as those with loops or conditional control flow. In such cases, you might need to provide mock return values for tasks when using the

visualize()

method. For more details, you can refer to the Prefect documentation on visualizing flow structure.

@Marvin, does the visualize method work well with async flows?

The

visualize()

method in Prefect does support async flows. However, it's important to note that when visualizing an async flow, the method will execute the flow's code that is not decorated with

@task

or

@flow

. This means that any code outside of these decorators will run, which could lead to unintended consequences. If your flow is asynchronous, the

visualize()

method will attempt to execute it using

await

. Just ensure that your environment is properly set up to handle asynchronous execution, and be cautious of any side effects from code execution during visualization. For more information, you can refer to the Prefect documentation on visualizing flow structure.

@Marvin, what is the file name of the png produced by visualize?

The documentation does not explicitly state the default file name for the PNG produced by the

visualize()

method. However, it mentions that in IPython notebooks, the visualization is rendered inline, and outside of notebooks, it is displayed in a new window as a PNG. This suggests that the output may not be saved to a file by default. If you need to save the visualization to a file, you might need to handle the output object from

visualize()

and specify the file name and format yourself. For more detailed instructions, you may want to consult the Prefect documentation on visualizing flow structure.