Merge pull request #219718 from davidmrdavid/dajusto/add-df-pystein-docs

Add DF docs for PyStein

Author: BCS2022

articles/azure-functions/functions-bindings-triggers-python.md

@@ -284,6 +284,126 @@ def test_function(mytimer: func.TimerRequest) -> None:
         logging.info('The timer is past due!')
     logging.info('Python timer trigger function ran at %s', utc_timestamp)
 ```
+
+## Durable Functions
+
+Durable Functions also provides preview support of the V2 programming model. To try it out, install the Durable Functions SDK (PyPI package `azure-functions-durable`) from version `1.2.2` or greater. You can reach us in the [Durable Functions SDK for Python repo](https://github.com/Azure/azure-functions-durable-python) with feedback and suggestions.
+
+
+> [!NOTE]
+> Using [Extension Bundles](/azure-functions/functions-bindings-register#extension-bundles) is not currently supported when trying out the Python V2 programming model with Durable Functions, so you will need to manage your extensions manually.
+> To do this, remove the `extensionBundles` section of your `host.json` as described [here](/azure-functions/functions-bindings-register#extension-bundles) and run `func extensions install --package Microsoft.Azure.WebJobs.Extensions.DurableTask --version 2.9.1` on your terminal. This will install the Durable Functions extension for your app and will allow you to try out the new experience.
+
+The Durable Functions Triggers and Bindings may be accessed from an instance `DFApp`, a subclass of `FunctionApp` that additionally exports Durable Functions-specific decorators. 
+
+Below is a simple Durable Functions app that declares a simple sequential orchestrator, all in one file!
+
+```python
+import azure.functions as func
+import azure.durable_functions as df
+
+myApp = df.DFApp(http_auth_level=func.AuthLevel.ANONYMOUS)
+
+# An HTTP-Triggered Function with a Durable Functions Client binding
+@myApp.route(route="orchestrators/{functionName}")
+@myApp.durable_client_input(client_name="client")
+async def durable_trigger(req: func.HttpRequest, client):
+    function_name = req.route_params.get('functionName')
+    instance_id = await client.start_new(function_name)
+    response = client.create_check_status_response(req, instance_id)
+    return response
+
+# Orchestrator
+@myApp.orchestration_trigger(context_name="context")
+def my_orchestrator(context):
+    result1 = yield context.call_activity("hello", "Seattle")
+    result2 = yield context.call_activity("hello", "Tokyo")
+    result3 = yield context.call_activity("hello", "London")
+
+    return [result1, result2, result3]
+
+# Activity
+@myApp.activity_trigger(input_name="myInput")
+def hello(myInput: str):
+    return "Hello " + myInput    
+```
+
+> [!NOTE]
+> Previously, Durable Functions orchestrators needed an extra line of boilerplate, usually at the end of the file, to be indexed:
+> `main = df.Orchestrator.create(<name_of_orchestrator_function>)`.
+> This is no longer needed in V2 of the Python programming model. This applies to Entities as well, which required a similar boilerplate through
+> `main = df.Entity.create(<name_of_entity_function>)`.
+
+For reference, all Durable Functions Triggers and Bindings are listed below:
+
+### Orchestration Trigger
+
+```python
+import azure.functions as func
+import azure.durable_functions as df
+
+myApp = df.DFApp(http_auth_level=func.AuthLevel.ANONYMOUS)
+
+@myApp.orchestration_trigger(context_name="context")
+def my_orchestrator(context):
+    result = yield context.call_activity("Hello", "Tokyo")
+    return result
+```
+
+### Activity Trigger
+
+```python
+import azure.functions as func
+import azure.durable_functions as df
+
+myApp = df.DFApp(http_auth_level=func.AuthLevel.ANONYMOUS)
+
+@myApp.activity_trigger(input_name="myInput")
+def my_activity(myInput: str):
+    return "Hello " + myInput
+```
+
+### DF Client Binding
+
+```python
+import azure.functions as func
+import azure.durable_functions as df
+
+myApp = df.DFApp(http_auth_level=func.AuthLevel.ANONYMOUS)
+
+@myApp.route(route="orchestrators/{functionName}")
+@myApp.durable_client_input(client_name="client")
+async def durable_trigger(req: func.HttpRequest, client):
+    function_name = req.route_params.get('functionName')
+    instance_id = await client.start_new(function_name)
+    response = client.create_check_status_response(req, instance_id)
+    return response
+```
+
+### Entity Trigger
+
+```python
+import azure.functions as func
+import azure.durable_functions as df
+
+myApp = df.DFApp(http_auth_level=func.AuthLevel.ANONYMOUS)
+
+@myApp.entity_trigger(context_name="context")
+def entity_function(context):
+    current_value = context.get_state(lambda: 0)
+    operation = context.operation_name
+    if operation == "add":
+        amount = context.get_input()
+        current_value += amount
+    elif operation == "reset":
+        current_value = 0
+    elif operation == "get":
+        pass
+    
+    context.set_state(current_value)
+    context.set_result(current_value)
+```
+
 ## Next steps
 
 + [Python developer guide](./functions-reference-python.md)