How to share configuration between workflows

Create a variable

To create a variable stored in the Prefect backend, use Variable.set().

from prefect.variables import Variable

Variable.set("answer", 42)

Read a variable

To read a variable, use Variable.get().

from prefect.variables import Variable

Variable.get("answer")

To read a variable with a fallback value, use Variable.get(default=...).

from prefect.variables import Variable

Variable.get("answer", default=42)

Update a variable

To update a variable, use Variable.set(value, overwrite=True).

from prefect.variables import Variable

Variable.set("answer", 42, overwrite=True)

Delete a variable

To delete a variable, use Variable.unset().

from prefect.variables import Variable

Variable.unset("answer")

In a sync context (such as an if __name__ == "__main__" block or simple def scope), these methods are used synchronously. In an async context (such as an async def scope), they are used asynchronously. </Warning>

from prefect import flow from prefect.variables import Variable

@flow(log_prints=True) def space_mission_sync(mission_name: str): crew = Variable.get("crew_members", default=["Backup1", "Backup2"]) print(f"Launching {mission_name} with crew: {', '.join(crew)}")

if name == "main": Variable.set("crew_members", ["Zaphod", "Arthur", "Trillian"]) space_mission_sync("Mars Expedition")

```python Asynchronous
import asyncio
from prefect import flow
from prefect.variables import Variable

@flow(log_prints=True)
async def space_mission_async(mission_name: str):
    crew = await Variable.get("crew_members", default=["Backup1", "Backup2"])
    print(f"Launching {mission_name} with crew: {', '.join(crew)}")

if __name__ == "__main__":
    Variable.set("crew_members", ["Zaphod", "Arthur", "Trillian"])
    asyncio.run(space_mission_async("Mars Expedition"))

Use variables in prefect.yaml deployment steps

In prefect.yaml files, variables are expressed as strings wrapped in quotes and double curly brackets:

"{{ prefect.variables.my_variable }}"

Use variables to templatize deployment steps by referencing them in the prefect.yaml file that creates the deployments.

For example, you can pass in a variable to specify a branch for a git repo in a deployment pull step:

pull:
- prefect.deployments.steps.git_clone:
    repository: https://github.com/PrefectHQ/hello-projects.git
    branch: "{{ prefect.variables.deployment_branch }}"

The deployment_branch variable is evaluated at runtime for the deployed flow, allowing changes to variables used in a pull action without updating a deployment directly.