This sample shows how to create a custom Pydantic converter to properly serialize Pydantic models.

For this sample, the optional pydantic dependency group must be included. To include, run:

poetry install --with pydantic

To run, first see README.md for prerequisites. Then, run the following from this directory to start the worker:

poetry run python worker.py

This will start the worker. Then, in another terminal, run the following to execute the workflow:

poetry run python starter.py

In the worker terminal, the workflow and its activity will log that it received the Pydantic models. In the starter terminal, the Pydantic models in the workflow result will be logged.

This is the preferred way to use Pydantic models with Temporal Python SDK. The converter code is small and meant to embed into other projects.

This sample also demonstrates use of datetime inside of Pydantic models. Due to a known issue with the Temporal sandbox, this class is seen by Pydantic as date instead of datetime upon deserialization. This is due to a known Python issue where, when we proxy the datetime class in the sandbox to prevent non-deterministic calls like now(), issubclass fails for the proxy type causing Pydantic to think it's a date instead. In worker.py, we have shown a workaround of disabling restrictions on datetime which solves this issue but no longer protects against workflow developers making non-deterministic calls in that module.