Tutorial: Configure a Python function with Azure Table Storage output

In this tutorial, you configure a Python function to use Azure Table Storage as an output binding. You then deploy the function to Azure Functions and use Service Connector to connect the Azure Functions app with Table Storage.

You use Visual Studio Code to complete the following tasks:

The Service Connector source service is Azure Functions and the target service is Azure Table Storage. The function binding uses an HTTP trigger with the storage table as output. The local and cloud authentication type is connection string.

Prerequisites

• Basic understanding of Azure Functions and how to connect to services in Azure Functions.
• An Azure subscription where you have Azure resource write permissions, in an Azure region that supports Service Connector. Create an Azure account for free.
• An Azure Storage Account in your Azure subscription, and a table named testTable in the storage account.
• Visual Studio Code, with the following extensions installed:
  • Python
  • Azure CLI Tools
  • Azure Functions, configured to allow Programming Model V1 as follows:
    1. In Visual Studio Code, select the Settings icon next to the Azure Functions extension and select Settings.
    2. On the Settings screen, select the checkbox next to Azure Functions: Allow Programming Model Selection.
    3. Close the Settings screen.

Create the function project

In Visual Studio Code, create a Python function project with an HTTP trigger.

1. Press F1 to open the command palette, and search for and select the command Azure Functions: Create New Project.
2. For Select the folder that will contain your function project, select Browse, and either create a new folder or choose an empty folder for the project workspace. Don't choose a project folder that's already part of a workspace.
3. For Select a project type, select Python.
4. For Select a Python programming model, select Model V1.
5. For Select a Python interpreter to create a virtual environment, select Manually enter Python interpreter or full path and enter the full path to your Python executable.
6. For Select a template for your project's first function, select HTTP trigger.
7. For Provide a function name, enter TableStorageOutputFunc.
8. For Authorization level, select Anonymous.
9. For Select how you would like to open your project, select Open in current window.

For more information, see Create and deploy function code to Azure using Visual Studio Code.

Add a storage table output binding

The following procedure edits the function.json and local.settings.json files in your project to create a table output binding for your function.

1. Right-click the function.json file in your function folder and select Add binding from the context menu.
2. In the command palette, for Select binding direction, select out.
3. For Select binding with direction "out", select Azure Table Storage.
4. For The name used to identify this binding in your code, enter outMessage.
5. For Table name in storage account where data will be written, enter testTable.
6. For Select the app setting with your Storage account connection string from "local.settings.json", select Create new local app setting.
7. For Select subscription, select your Azure subscription.
8. For Select a storage account type for development, select Use Azure Storage for remote storage.
9. For Select a storage account, select the Azure Storage account to use for output.

Check the added binding

• Open the TableStorageOutputFunc/function.json file and make sure the table output binding is correctly added to the file. If any of the values differ, edit them to the following values:

      {
        "type": "table",
        "direction": "out",
        "name": "outMessage",
        "tableName": "testtable",
        "connection": "<your-storage-account-name>_STORAGE"
      }
  

• Open the local.settings.json file and make sure the following key-value pair is in this file: <your-storage-account-name>_STORAGE: <your-storage-account-connection-string>.

Edit the Python code

Open the TableStorageOutputFunc/__init__.py file and replace its contents with the following code:

import logging
import uuid
import json
import azure.functions as func

def main(req: func.HttpRequest, outMessage: func.Out[str]) -> func.HttpResponse:

    rowKey = str(uuid.uuid4())
    data = {
        "Name": "Output binding message",
        "PartitionKey": "message",
        "RowKey": rowKey
    }

    outMessage.set(json.dumps(data))
    return func.HttpResponse(f"Message created with the rowKey: {rowKey}")

Run the function locally

To run the function locally, press F5. If prompted to connect to a storage account, select an Azure Storage account. This value is used for the Azure Functions runtime and can be, but doesn't have to be the same storage account you use for the function output.

While the function is running, verify that it can write to your Table Storage table by right-clicking the TableStorageOutputFunc function in the Workspace view of the Activity bar and selecting Execute Function Now. Check the function response to make sure it contains a rowKey value that was written to the table.

Deploy your function to Azure

Create an Azure Functions app and deploy your function to Azure.

1. In your project function.json file, change the value of the connection property in bindings to AZURE_STORAGETABLE_CONNECTIONSTRING.
2. Press F1 to open the command palette, and search for and select the command Azure Functions: Deploy to Function App.
3. For Select subscription, select your Azure subscription.
4. For Select a function app, select Create new Function App.
5. For Select a location for new resources, select an Azure region for your Azure Functions app, preferably the same region as your Storage account.
6. For Enter a name for the new function app, you can enter the same name as your local function, TableStorageOutputFunc.
7. For Select a runtime stack, select Python 3.10.
8. For Select resource authentication type, select Secrets.

Create a connection using Service Connector

After you create the Functions app, you can use Service Connector to connect the app to your Table Storage table, so your app can easily write output to your storage account. The following command creates a Service Connector resource that configures the AZURE_STORAGETABLE_CONNECTIONSTRING variable in the function's App Settings.

The function binding consumes this app setting to connect to the storage account so the function can write to the storage table. For more information, see How Service Connector helps Azure Functions connect to services.

To create the connection, you can run the following Azure CLI command in Visual Studio Code, or use Azure Cloud Shell or local Azure CLI. Replace the placeholder values as follows:

• <function-resource-id>:
  /subscriptions/<your-subscription>/resourceGroups/<function-resource-group>/providers/Microsoft.Web/sites/<function-name>

• <storage-resource-id>:
  /subscriptions/<your-subscription>/resourceGroups/<storage-resource-group>/providers/Microsoft.Storage/storageAccounts/<storage-account>/tableServices/default

az functionapp connection create storage-table --source-id "<function-resource-id>" --target-id "<storage-resource-id>" --secret

Troubleshoot

If you get errors related to the storage host, such as No such host is known (<account-name>.table.core.windows.net:443), make sure the connection string used to connect to Table Storage contains the table endpoint. If not, go to the Azure Storage page, copy the connection string from Access keys under Security + networking, and replace the value.

If this error occurs when you run locally, check the local.settings.json file. If the error occurs when you deploy your function to Azure, check the Functions app's App Settings.

Clean up resources

If you no longer want the Azure resources you created for this tutorial, you can delete them.

• In the Azure portal, open the Functions app or Storage account resource and select Delete from the top menu bar. Enter the resource name and select Delete.

• In Azure CLI, run one or both of the following commands, replacing the placeholders with your own information.

  az functionapp delete --name <functionapp-name> --resource-group <functionapp-resource-group>
  az storage account delete --name <storageaccount-name> --resource-group <storageaccount-resource-group>
  

Related content

• Service Connector concepts
• Use Service Connector to connect Azure Functions to other cloud services