Feature Request | Add the ability to define workflows in Python

[ccrvlh]

Hi guys,
It would be great to have the option to define a workflow in Python instead of only in YAML.

From the workflows engines that I know, maybe Prefect could be a good benchmark for implementation.
This would require writing a lot of methods to define the dependency chain (set_upstream, set_downstream and etc.).

Another option that could be simpler and work as well, would be define the workflow as dictionary (or an OrderedDict), and than just add a parser, so the dict would be read just as the YAML is at the moment: this could probably work just adding a single parser method in the CeleryWorkflow class I guess. Saltstack uses this kind of implementation beautifuly as it allows for the definition of "states" in pretty much anything (jinja, yaml, json, python, py functions etc). These are called Renderes if you guys would like to take a look.

I would be open to contribute as well, I will take a deeper look at the YAML parser and see what could be done.
What you guys think about this feature?

Thanks a lot, very nice project, thanks a lot for sharing!