Use Azure Pipelines to build and deploy a Python web app to Azure App Service

Azure DevOps Services

Use Azure Pipelines for continuous integration and continuous delivery (CI/CD) to build and deploy a Python web app to Azure App Service on Linux. Your pipeline automatically builds and deploys your Python web app to App Service whenever there's a commit to the repository.

In this article, you learn how to:

• Create a web app in Azure App Service.
• Create a project in Azure DevOps.
• Connect your DevOps project to Azure.
• Create a Python-specific pipeline.
• Run the pipeline to build and deploy your app to your web app in App Service.

Prerequisites

• An Azure subscription. If you don't have one, create a free account.
• A GitHub account. If you don't have one, create one for free.
• An Azure DevOps Services organization. Create one for free.

Create a repository for your app code

Fork the sample repository at https://github.com/Microsoft/python-sample-vscode-flask-tutorial to your GitHub account.

On your local host, clone your GitHub repository. Use the following command, replacing <repository-url> with the URL of your forked repository.

git clone <repository-url>

Test your app locally

Build and run the app locally to make sure it works.

1. Change to the cloned repository folder.

   cd python-sample-vscode-flask-tutorial
   

2. Build and run the app

   Linux

   python -m venv .env
   source .env/bin/activate
   pip install --upgrade pip
   pip install -r ./requirements.txt
   export set FLASK_APP=hello_app.webapp
   python3 -m flask run
   

   PowerShell

   py -m venv .env
   .env\scripts\activate
   pip install -r ./requirements.txt
   $env:FLASK_APP = "hello_app.webapp"
   flask run
   

3. To view the app, open a browser window and go to http://localhost:5000. Verify that you see the title Visual Studio Flask Tutorial.

4. When you're finished, close the browser window and stop the Flask server with Ctrl+C.

Open a Cloud Shell

1. Sign in to the Azure portal at https://portal.azure.com.

2. Open the Azure CLI by selecting the Cloud Shell button on the portal toolbar.

   

3. The Cloud Shell appears along the bottom of the browser. Select Bash from the dropdown menu.

   

4. To give you more space to work, select the maximize button.

Create an Azure App Service web app

Create your Azure App Service web app from the Cloud Shell in the Azure portal.

Tip

To paste into the Cloud Shell, use Ctrl+Shift+V or right-click and select Paste from the context menu.

1. Clone your repository with the following command, replacing <repository-url> with the URL of your forked repository.

   git clone <repository-url>
   

2. Change directory to the cloned repository folder, so the az webapp up command recognizes the app as a Python app.

   cd python-sample-vscode-flask-tutorial
   

3. Use the az webapp up command to both provision the App Service and do the first deployment of your app. Replace <your-web-app-name> with a name that is unique across Azure. Typically, you use a personal or company name along with an app identifier, such as <your-name>-flaskpipelines. The app URL becomes <your-appservice>.azurewebsites.net.

   az webapp up --name <your-web-app-name>
   

   The JSON output of the az webapp up command shows:

   {
     "URL": <your-web-app-url>,
     "appserviceplan": <your-app-service-plan-name>,
     "location": <your-azure-location>,
     "name": <your-web-app-name>,
     "os": "Linux",
     "resourcegroup": <your-resource-group>,
     "runtime_version": "python|3.11",
     "runtime_version_detected": "-",
     "sku": <sku>,
     "src_path": <repository-source-path>
   }
   

   Note the URL and the runtime_version values. You use the runtime_version in the pipeline YAML file. The URL is the URL of your web app. You can use it to verify that the app is running.

   Note

   The az webapp up command does the following actions:

   • Create a default resource group.

   • Create a default App Service plan.

   • Create an app with the specified name.

   • Zip deploy all files from the current working directory, with build automation enabled.

   • Cache the parameters locally in the .azure/config file so that you don't need to specify them again when deploying later with az webapp up or other az webapp commands from the project folder. The cached values are used automatically by default.

   You can override the default action with your own values using the command parameters. For more information, see az webapp up.

4. The python-sample-vscode-flask-tutorial app has a startup.txt file that contains the specific startup command for the web app. Set the web app startup-file configuration property to startup.txt.

   1. From the az webapp up command output, copy the resourcegroup value.

   2. Enter the following command, using the resource group and your app name.

   az webapp config set --resource-group <your-resource-group> --name <your-web-app-name> --startup-file startup.txt
   

   When the command completes, it shows JSON output that contains all of the configuration settings for your web app.

5. To see the running app, open a browser and go to the URL shown in the az webapp up command output. If you see a generic page, wait a few seconds for the App Service to start, then refresh the page. Verify that you see the title Visual Studio Flask Tutorial.

Create an Azure DevOps project

Create a new Azure DevOps project.

1. In a browser, go to dev.azure.com and sign in.
2. Select your organization.
3. Create a new project by selecting New project or Create project if creating the first project in the organization.
4. Enter a Project name.
5. Select the Visibility for your project.
6. Select Create.

Create a service connection

A service connection allows you to create a connection to provide authenticated access from Azure Pipelines to external and remote services. To deploy to your Azure App Service web app, create a service connection to the resource group containing the web app.

1. On project page, select Project settings.

   

2. Select Service connections in the Pipelines section of the menu.

3. Select Create service connection.

4. Select Azure Resource Manager and select Next.

   

5. Select your authentication method and select Next.

6. In the New Azure service connection dialog, enter the information specific to the selected authentication method. For more information about authentication methods, see Connect to Azure by using an Azure Resource Manager service connection.

   For example, if you're using a Workload Identity federation (automatic) or Service principal (automatic) authentication method, enter the required information.

   

   Field	Description
   Scope level	Select Subscription.
   Subscription	Your Azure subscription name.
   Resource group	The name of the resource group containing your web app.
   Service connection name	A descriptive name for the connection.
   Grant access permissions to all pipelines	Select this option to grant access to all pipelines.

7. Select Save.

The new connection appears in the Service connections list, and is ready for use in your Azure Pipeline.

Create a pipeline

Create a pipeline to build and deploy your Python web app to Azure App Service. To understand pipeline concepts, watch:

1. On the left navigation menu, select Pipelines.

   

2. Select Create Pipeline.

   

3. In the Where is your code dialog, select GitHub. You might be prompted to sign into GitHub.

   

4. On the Select a repository screen, select the forked sample repository.

   

5. You might be prompted to enter your GitHub password again as a confirmation.

6. If the Azure Pipelines extension isn't installed on GitHub, GitHub prompts you to install the Azure Pipelines extension.

   

   On this page, scroll down to the Repository access section, choose whether to install the extension on all repositories or only selected ones, and then select Approve and install.

   

7. In the Configure your pipeline dialog, select Python to Linux Web App on Azure.

8. Select your Azure subscription and select Continue.

9. If you're using your username and password to authenticate, a browser opens for you to sign in to your Microsoft account.

10. Select your web app name from the dropdown list and select Validate and configure.

Azure Pipelines creates a azure-pipelines.yml file and displays it in the YAML pipelines editor. The pipeline file defines your CI/CD pipeline as a series of stages, Jobs, and steps, where each step contains the details for different tasks and scripts. Take a look at the pipeline to see what it does. Make sure all the default inputs are appropriate for your code.

YAML pipeline file

The following explanation describes the YAML pipeline file. To learn about the pipeline YAML file schema, see YAML schema reference.

Variables

The variables section contains the following variables:

variables:
# Azure Resource Manager connection created during pipeline creation
azureServiceConnectionId: '<GUID>'

# Web app name
webAppName: '<your-web-app-name>'

# Agent VM image name
vmImageName: 'ubuntu-latest'

# Environment name
environmentName: '<your-web-app-name>'

# Project root folder.
projectRoot: $(System.DefaultWorkingDirectory)

# Python version: 3.11. Change this to match the Python runtime version running on your web app.
pythonVersion: '3.11'

Variable	Description
azureServiceConnectionId	The ID or name of the Azure Resource Manager service connection.
webAppName	The name of the Azure App Service web app.
vmImageName	The name of the operating system to use for the build agent.
environmentName	The name of the environment used in the deployment stage. The environment is automatically created when the stage job is run.
projectRoot	The root folder containing the app code.
pythonVersion	The version of Python to use on the build and deployment agents.

Build stage

The build stage contains a single job that runs on the operating system defined in the vmImageName variable.

  - job: BuildJob
    pool:
      vmImage: $(vmImageName)

The job contains multiple steps:

1. The UsePythonVersion task selects the version of Python to use. The version is defined in the pythonVersion variable.

      - task: UsePythonVersion@0
         inputs:
           versionSpec: '$(pythonVersion)'
           displayName: 'Use Python $(pythonVersion)'
   

2. This step uses a script to create a virtual Python environment and install the app's dependencies contained in the requirements.txt file. The --target parameter specifies the location to install the dependencies. The workingDirectory parameter specifies the location of the app code.

     - script: |
          python -m venv antenv
          source antenv/bin/activate
          python -m pip install --upgrade pip
          pip install setup
          pip install --target="./.python_packages/lib/site-packages" -r ./requirements.txt
        workingDirectory: $(projectRoot)
        displayName: "Install requirements"
   

3. The ArchiveFiles task creates the .zip archive containing the web app. The .zip file is uploaded to the pipeline as the artifact named drop. The .zip file is used in the deployment stage to deploy the app to the web app.

      - task: ArchiveFiles@2
        displayName: 'Archive files'
        inputs:
          rootFolderOrFile: '$(projectRoot)'
          includeRootFolder: false
          archiveType: zip
          archiveFile: $(Build.ArtifactStagingDirectory)/$(Build.BuildId).zip
          replaceExistingArchive: true
   
      - upload: $(Build.ArtifactStagingDirectory)/$(Build.BuildId).zip
        displayName: 'Upload package'
        artifact: drop
   

   Parameter	Description
   rootFolderOrFile	The location of the app code.
   includeRootFolder	Indicates whether to include the root folder in the .zip file. Set this parameter to false otherwise, the contents of the .zip file are put in a folder named s and App Service on Linux container can't find the app code.
   archiveType	The type of archive to create. Set to zip.
   archiveFile	The location of the .zip file to create.
   replaceExistingArchive	Indicates whether to replace an existing archive if the file already exists. Set to true.
   upload	The location of the .zip file to upload.
   artifact	The name of the artifact to create.

Deployment stage

The deployment stage is run if the build stage completes successfully. The following keywords define this behavior:

  dependsOn: Build
  condition: succeeded()

The deployment stage contains a single deployment job configured with the following keywords:

  - deployment: DeploymentJob
    pool:
      vmImage: $(vmImageName)
    environment: $(environmentName)

Keyword	Description
deployment	Indicates that the job is a deployment job targeting an environment.
pool	Specifies deployment agent pool. The default agent pool if the name isn't specified. The vmImage keyword identifies the operating system for the agent's virtual machine image
environment	Specifies the environment to deploy to. The environment is automatically created in your project when the job is run.

The strategy keyword is used to define the deployment strategy. The runOnce keyword specifies that the deployment job runs once. The deploy keyword specifies the steps to run in the deployment job.

  strategy:
    runOnce:
      deploy:
        steps:

The steps in the pipeline are:

1. Use the UsePythonVersion task to specify the version of Python to use on the agent. The version is defined in the pythonVersion variable.

    - task: UsePythonVersion@0
      inputs:
        versionSpec: '$(pythonVersion)'
      displayName: 'Use Python version'
   

2. Deploy the web app using the AzureWebApp@1. This task deploys the pipeline artifact drop to your web app.

   - task: AzureWebApp@1
      displayName: 'Deploy Azure Web App : <your-web-app-name>'
      inputs:
         azureSubscription: $(azureServiceConnectionId)
         appName: $(webAppName)
         package: $(Pipeline.Workspace)/drop/$(Build.BuildId).zip
   

   Parameter	Description
   azureSubscription	The Azure Resource Manager service connection ID or name to use.
   appName	The name of the web app.
   package	The location of the .zip file to deploy.

   Also, because the python-vscode-flask-tutorial repository contains the same startup command in a file named startup.txt, you can specify that file by adding the parameter: startUpCommand: 'startup.txt'.

Run the pipeline

You're now ready to try it out!

1. In the editor, select Save and run.

2. In the Save and run dialog, add a commit message then select Save and run.

   You can watch the pipeline as it runs by selecting the Stages or Jobs in the pipeline run summary.

   

   There are green check marks next to each stage and job as it completes successfully. If errors occur, they're displayed in the summary or in the job steps.

   

   You can quickly return to the YAML editor by selecting the vertical dots at the upper right of the Summary page and selecting Edit pipeline:

   

3. From the deployment job, select the Deploy Azure Web App task to display its output. To visit the deployed site, hold down Ctrl and select the URL after App Service Application URL.

   If you're using the sample app, the app should appear as follows:

   

Important

If your app fails because of a missing dependency, then your requirements.txt file was not processed during deployment. This behavior happens if you created the web app directly on the portal rather than using the az webapp up command as shown in this article.

The az webapp up command specifically sets the build action SCM_DO_BUILD_DURING_DEPLOYMENT to true. If you provisioned the app service through the portal, this action is not automatically set.

The following steps set the action:

1. Open the Azure portal, select your App Service, then select Configuration.
2. Under the Application Settings tab, select New Application Setting.
3. In the popup that appears, set Name to SCM_DO_BUILD_DURING_DEPLOYMENT, set Value to true, and select OK.
4. Select Save at the top of the Configuration page.
5. Run the pipeline again. Your dependencies should be installed during deployment.

Trigger a pipeline run

To trigger a pipeline run, commit a change to the repository. For example, you can add a new feature to the app, or update the app's dependencies.

1. Go to your GitHub repository.
2. Make a change to the code, such as changing the title of the app.
3. Commit the change to your repository.
4. Go to your pipeline and verify a new run is created.
5. When the run completes, verify the new build is deployed to your web app.
   1. In the Azure portal, go to your web app.
   2. Select Deployment Center and select the Logs tab.
   3. Verify that the new deployment is listed.

Considerations for Django

You can use Azure Pipelines to deploy Django apps to Azure App Service on Linux if you're using a separate database. You can't use a SQLite database, because App Service locks the db.sqlite3 file, preventing both reads and writes. This behavior doesn't affect an external database.

As described in Configure Python app on App Service - Container startup process, App Service automatically looks for a wsgi.py file within your app code, which typically contains the app object. If you want to customize the startup command in any way, use the startUpCommand parameter in the AzureWebApp@1 step of your YAML pipeline file, as described in the previous section.

When using Django, you typically want to migrate the data models using manage.py migrate after deploying the app code. You can add startUpCommand with the post-deployment script for this purpose:

startUpCommand:  python manage.py migrate

Run tests on the build agent

As part of your build process, you might want to run tests on your app code. Tests run on the build agent, so you need to install your dependencies into a virtual environment on the build agent. After the tests run, delete the virtual environment before you create the .zip file for deployment. The following script elements illustrate this process. Place them before the ArchiveFiles@2 task in the azure-pipelines.yml file. For more information, see Run cross-platform scripts.

# The | symbol is a continuation character, indicating a multi-line script.
# A single-line script can immediately follow "- script:".
- script: |
    python -m venv .env
    source .env/bin/activate
    pip install setuptools
    pip install -r requirements.txt

  # The displayName shows in the pipeline UI when a build runs
  displayName: 'Install dependencies on build agent'

- script: |
    # Put commands to run tests here
    displayName: 'Run tests'

- script: |
    echo Deleting .env
    deactivate
    rm -rf .env
  displayName: 'Remove .env before zip'

You can also use a task like PublishTestResults@2 to publish the test results to your pipeline. For more information, see Build Python apps - Run tests.

Clean up resources

To avoid incurring charges on the Azure resources created in this tutorial:

• Delete the project that you created. Deleting the project deletes the pipeline and service connection.

• Delete the Azure resource group that contains the App Service and the App Service Plan. In the Azure portal, go to the resource group, select Delete resource group, and follow the prompts.

• Delete the storage account that maintains the file system for Cloud Shell. Close the Cloud Shell then go to the resource group that begins with cloud-shell-storage-, select Delete resource group, and follow the prompts.

Next steps

• Customize Python apps in Azure Pipelines
• Configure Python app on App Service