@Marvin I'm on prefect 2 and using "pydantic >= 2.7, < 3.0.0" but I am getting the following error: Encountered exception during execution: Traceback (most recent call last): File "/usr/local/lib/python3.11/dist-packages/prefect/engine.py", line 877, in orchestrate_flow_run result = await flow_call.aresult() ^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/local/lib/python3.11/dist-packages/prefect/_internal/concurrency/calls.py", line 327, in aresult return await asyncio.wrap_future(self.future) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/local/lib/python3.11/dist-packages/prefect/_internal/concurrency/calls.py", line 389, in _run_async result = await coro ^^^^^^^^^^ File "/workflows/echo_localization/inspection_flows.py", line 166, in inspection_flow results = [await result.state.result(fetch=True) for result in awaited] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/workflows/echo_localization/inspection_flows.py", line 166, in results = [await result.state.result(fetch=True) for result in awaited] ^^^^^^^^^^^^ AttributeError: 'TypeError' object has no attribute 'state'

It seems like the error you're encountering may be due to a compatibility issue between Prefect 2.x and Pydantic. Specifically, Prefect's handling of state objects and their attributes might not be compatible with the version constraints of Pydantic you're using, especially surrounding asynchronous handling of states and their results. Here's some key insights and potential resolutions: 1. Understanding the Error: - The error indicates that a

TypeError

object is being accessed as if it had an attribute

state

. This might arise if there is some logic that fails before the expected result object is set correctly, thereby causing an exception during its assignment or fetching. - The provided code snippets from the Prefect 2.x documentation illustrate the usage of

State.result()

, which must be awaited when fetching a result. 2. Potential Solutions: - Check if the error is caused by invalid task or state management leading to a TypeError, which doesn't possess a

state

. Review the flow code to ensure that the expected task returns are successfully loaded into a state. - Ensure the Prefect usage follows the latest guidelines, where

State.result()

uses

await

with

fetch=True

for proper asynchronous operation. - Verify no deprecated usage is employed. Prefect documentation indicates that prior to version 2.6.0,

State.result()

did not require awaiting. Presumably, both Prefect and your Pydantic versions must support this functionality. 3. Possible Compatibility Fixes: - Double-check that all dependencies, especially Prefect and Pydantic, are compatible. - Consider reviewing and potentially updating or downgrading the Pydantic version if the version boundary condition is proving problematic. For detailed guidance on Prefect state handling, you can refer to the following documentation pages: - Prefect State Concepts - Prefect Results Concepts If you continue to face issues, it may also help to explore open issues related to Prefect and Pydantic on GitHub for any known and possibly resolved compatibility issues.

@Marvin If I await a list of flow to finish, how would I access the result

When you await a list of flows in Prefect 2.x, you can access their results by managing the flow states and using the

State.result()

method. Here's a basic approach using asynchronous workflows: 1. Run and Await Flows: When you have multiple flows you want to execute and await, you typically call them asynchronously within an async function. 2. Access Results via State: After awaiting the flows, you retrieve their results using

await state.result(fetch=True)

. This method fetches the execution result from the state of each flow. Here's a simple code example:

python
import asyncio
from prefect import flow

@flow
async def flow_a():
    return "Result from flow A"

@flow
async def flow_b():
    return "Result from flow B"

async def main():
    # Run flows and gather their states
    states = await asyncio.gather(flow_a(return_state=True), flow_b(return_state=True))
    
    # Access and print results
    for state in states:
        result = await state.result(fetch=True)
        print(result)

# Run the main function
asyncio.run(main())

### Key Points: - Async and Await: Prefect flows can be called using

await

to run asynchronously, allowing you to manage multiple flows concurrently. - Fetch True: The

fetch=True

option ensures the result is retrieved correctly. Without this, you might only get a reference to the state's future. For further details on handling flow and task states and their results, you can explore the Prefect 2.x Documentation on Flow states and results.

@Marvin after updated to pydantic 2 I get a tonne of wierd issues. I has a list of FlowRuns generated from run_deployment and when I do awaited: list[FlowRun] = await asyncio.gather(*futures, return_exceptions=True), the subflows don't even get run

The issues you're experiencing when updating to Pydantic 2, particularly with running subflows and using

asyncio.gather

, could be due to several factors, including potential compatibility problems or incorrect usage of Prefect's async mechanisms. ### Understanding and Resolving the Issue: 1. Subflows and Asynchronous Execution: - Subflows in Prefect need to be properly set up to ensure they run asynchronously. The use of

asyncio.gather()

is intended for concurrent execution but might exhibit issues if the subflows are improperly structured or if there are hidden dependency restrictions. - Ensure that your

run_deployment

calls are correctly set up within tasks and that these tasks are run correctly within a main flow. This separation helps maintain clarity in what runs synchronously versus asynchronously. 2. Pydantic Compatibility: - Updating to Pydantic 2 could introduce changes in behavior that affect Prefect's handling of asynchronous flows or their setups. It's crucial to verify that these versions are compatible with your specific Prefect setup. - Prefect's documentation on deployment and subflow execution provides examples of how to structure subflows with

run_deployment

, ensuring dependencies and flows cooperate correctly. 3. Known Issues and Fixes: - There might be existing issues or guidance for users running into similar scenarios on GitHub or Prefect's forums. I couldn't find a directly related open issue, but you might want to keep an eye on or report your issue for further assistance. - Refer to the Prefect Deployment Documentation for guidance on using

run_deployment

, and ensure the

await

logic is correct. ### Troubleshooting Steps: - Debugging: Introduce logging to check if the tasks for subflows are being initiated and to trace where or why they might not run. - Isolation: Temporarily revert to the last known working version to ensure the issue results from the Pydantic update or Prefect's usage. - Verification: Double-check Pydantic and Prefect versions for compatibility notes, especially related to the async functionalities in both libraries. For a more permanent resolution, maintain documented structures for handling asynchronous Prefect flows and consult the detailed examples and community support resources available.