Azure Automation now supports Python 3 cloud & hybrid runbook execution in public preview. The support is available in all the public cloud regions.
You can import, author, and run Python 3 runbooks in Azure or in a Hybrid Runbook Worker. This includes the ability to upload Python 3 packages to be imported by Python 3 runbooks running in Azure. It also includes scheduling and interacting with other Automation resources, such as variables, connections, and credentials.

You can learn more about Python 3 runbook execution in the documentation Create a Python runbook & Manage Python 3 packages in Azure Automation