[BREAKING] Python: Refactor workflow events to unified discriminated union pattern (#3690)

* Refactor events

* Merge main

* Fixes

* Cleanup

* Update samples and tests

* Remove unused imports

* PR feedback

* Merge main. Add properties for events to help typing

* Formatting

* Cleanup

* use builtins.type to avoid shadowing by WorkflowEvent.type attribute

* Final improvements

python/samples/getting_started/workflows/control-flow/multi_selection_edge_group.py

@@ -16,7 +16,6 @@ from agent_framework import (
     WorkflowBuilder,
     WorkflowContext,
     WorkflowEvent,
-    WorkflowOutputEvent,
     executor,
 )
 from agent_framework.azure import AzureOpenAIChatClient
@@ -279,7 +278,7 @@ async def main() -> None:
     async for event in workflow.run(email, stream=True):
         if isinstance(event, DatabaseEvent):
             print(f"{event}")
-        elif isinstance(event, WorkflowOutputEvent):
+        elif event.type == "output":
             print(f"Workflow output: {event.data}")
 
     """

python/samples/getting_started/workflows/control-flow/sequential_executors.py

@@ -7,7 +7,6 @@ from agent_framework import (
     Executor,
     WorkflowBuilder,
     WorkflowContext,
-    WorkflowOutputEvent,
     handler,
 )
 from typing_extensions import Never
@@ -77,7 +76,7 @@ async def main() -> None:
     outputs: list[str] = []
     async for event in workflow.run("hello world", stream=True):
         print(f"Event: {event}")
-        if isinstance(event, WorkflowOutputEvent):
+        if event.type == "output":
             outputs.append(cast(str, event.data))
 
     if outputs:

python/samples/getting_started/workflows/control-flow/sequential_streaming.py

@@ -2,7 +2,7 @@
 
 import asyncio
 
-from agent_framework import WorkflowBuilder, WorkflowContext, WorkflowOutputEvent, executor
+from agent_framework import WorkflowBuilder, WorkflowContext, executor
 from typing_extensions import Never
 
 """
@@ -14,7 +14,8 @@ The second reverses the text and yields the workflow output. Events are printed
 Purpose:
 Show how to declare executors with the @executor decorator, connect them with WorkflowBuilder,
 pass intermediate values using ctx.send_message, and yield final output using ctx.yield_output().
-Demonstrate how streaming exposes ExecutorInvokedEvent and ExecutorCompletedEvent for observability.
+Demonstrate how streaming exposes executor_invoked events (type='executor_invoked') and 
+executor_completed events (type='executor_completed') for observability.
 
 Prerequisites:
 - No external services required.
@@ -67,17 +68,17 @@ async def main():
     async for event in workflow.run("hello world", stream=True):
         # You will see executor invoke and completion events as the workflow progresses.
         print(f"Event: {event}")
-        if isinstance(event, WorkflowOutputEvent):
+        if event.type == "output":
             print(f"Workflow completed with result: {event.data}")
 
     """
     Sample Output:
 
-    Event: ExecutorInvokedEvent(executor_id=upper_case_executor)
-    Event: ExecutorCompletedEvent(executor_id=upper_case_executor)
-    Event: ExecutorInvokedEvent(executor_id=reverse_text_executor)
-    Event: ExecutorCompletedEvent(executor_id=reverse_text_executor)
-    Event: WorkflowOutputEvent(data='DLROW OLLEH', executor_id=reverse_text_executor)
+    Event: executor_invoked event (type='executor_invoked', executor_id=upper_case_executor)
+    Event: executor_completed event (type='executor_completed', executor_id=upper_case_executor)
+    Event: executor_invoked event (type='executor_invoked', executor_id=reverse_text_executor)
+    Event: executor_completed event (type='executor_completed', executor_id=reverse_text_executor)
+    Event: output event (type='output', data='DLROW OLLEH', executor_id=reverse_text_executor)
     Workflow completed with result: DLROW OLLEH
     """
 

python/samples/getting_started/workflows/control-flow/simple_loop.py

@@ -9,7 +9,6 @@ from agent_framework import (
     ChatAgent,
     ChatMessage,
     Executor,
-    ExecutorCompletedEvent,
     WorkflowBuilder,
     WorkflowContext,
     handler,
@@ -143,7 +142,7 @@ async def main():
     # Step 2: Run the workflow and print the events.
     iterations = 0
     async for event in workflow.run(NumberSignal.INIT, stream=True):
-        if isinstance(event, ExecutorCompletedEvent) and event.executor_id == "guess_number":
+        if event.type == "executor_completed" and event.executor_id == "guess_number":
             iterations += 1
         print(f"Event: {event}")