I've been following along https://dataflow.spring.io/docs/recipes/polyglot/processor/
It looks like it requires dockerhub in order to use python with spring cloud data flow. Is it possible to run a polyglot application without dockerhub?
Yes, you can still run your polyglot app without docker. There are out of the box apps available to support running python script as a processor app.
But, remember that when using these out-of-box apps you don't have to write any python code to produce/consume messages from the messaging platform (Kafka etc.,). It is taken care by the binder you choose on these apps. That is a fundamental difference between what you saw from the docker based recipe(which needs you to write explicit code to produce/consume data to/from Kafka) and the above out of the box python processors.