Quickstart for Python App Engine Standard Environment

Python 2.7/3.7 |Java 8/11 |PHP 5/7 |Go 1.9/1.11/1.12 |Node.js

This quickstart shows you how to create a small App Engine application that displays a short message.

Costs

There are no costs associated with running this guide. Running this sample app alone does not exceed your free quota.

Before you begin

Before running and deploying this quickstart, install the Cloud SDK and then set up a GCP project for App Engine:

1. Download and install Cloud SDK:

   Download the SDK

   Note: If you already have the Cloud SDK installed, update it by running the following command:

   gcloud components update
   

2. Create a new project:

   gcloud projects create [YOUR_PROJECT_NAME] --set-as-default
   

   Verify the project was created:

   gcloud projects describe [YOUR_PROJECT_NAME]
   

   You see project details that might look like the following:

   createTime: year-month-hour
   lifecycleState: ACTIVE
   name: project-name
   parent:
   id: '433637338589'
   type: organization
   projectId: project-name-id
   projectNumber: 499227785679
   

3. Initialize your App Engine app with your project and choose its region:

   gcloud app create --project=[YOUR_PROJECT_NAME]
   

   When prompted, select the region where you want your App Engine application located.

   Caution: You cannot change an app's region once it has been set.

4. Install the following prerequisites:

   • Download and install Git.

• Run the following command to install the gcloud component that includes the App Engine extension for Python:

  gcloud components install app-engine-python
  

5. Prepare your environment for Python development. It is recommended that you have the latest version of Python, pip, virtualenv and other related tools installed on your system. For instructions, refer to the Python Development Environment Setup Guide.

App Engine locations

App Engine is regional, which means the infrastructure that runs your apps is located in a specific region and is managed by Google to be redundantly available across all the zones within that region.

Meeting your latency, availability, or durability requirements are primary factors for selecting the region where your apps are run. You can generally select the region nearest to your app's users but you should consider the location of the other GCP products and services that are used by your app. Using services across multiple locations can affect your app's latency as well as pricing.

App Engine is available in the following regions:

• northamerica-northeast1 (Montréal)
• us-central (Iowa)
• us-west2 (Los Angeles)
• us-east1 (South Carolina)
• us-east4 (Northern Virginia)
• southamerica-east1 (São Paulo)
• europe-west (Belgium)
• europe-west2 (London)
• europe-west3 (Frankfurt)
• europe-west6 (Zürich)
• asia-northeast1 (Tokyo)
• asia-northeast2 (Osaka)
• asia-east2 (Hong Kong)
• asia-south1 (Mumbai)
• australia-southeast1 (Sydney)

You cannot change an app's region after you set it.

If you already created an App Engine application, you can view the region by running the gcloud app describe command or opening the App Engine Dashboard in the GCP Console. The region of your App Engine application is listed under http://[YOUR_PROJECT_ID].appspot.com.

OK

This quickstart demonstrates a simple Python app written with the Flask web framework that can be deployed to App Engine. Although this sample uses Flask, you can use any web framework that satisfies the requirements above. Alternative frameworks include Django, Pyramid, Bottle, and web.py.

Download the Hello World app

We've created a simple Hello World app for Python so you can quickly get a feel for deploying an app to Google Cloud Platform. Follow these steps to download Hello World to your local machine.

1. Clone the Hello World sample app repository to your local machine:

   git clone https://github.com/GoogleCloudPlatform/python-docs-samples
   

2. Change to the directory that contains the sample code:

   cd python-docs-samples/appengine/standard/hello_world
   

Alternatively, you can download the sample as a .zip file and extract it.

Test the application

Test the application using the local development server (dev_appserver.py), which is included with the SDK.

1. From within the hello_world directory where the app's app.yaml configuration file is located, start the local development server with the following command:

   dev_appserver.py app.yaml
   

   The local development server is now running and listening for requests on port 8080. Something go wrong?

   1. Visit http://localhost:8080/ in your web browser to view the app.

Running the local development server (dev_appserver.py)

To run the local development server, you can either run dev_appserver.py by specifying the full directory path or you can add dev_appserver.py to your PATH environment variable:

• If you installed the original App Engine SDK, the tool is located at:

  [PATH_TO_APP_ENGINE_SDK]/dev_appserver.py
  

• If you installed the Google Cloud SDK, the tool is located at:

  [PATH_TO_CLOUD_SDK]/google-cloud-sdk/bin/dev_appserver.py
  

  Tip: To add the Google Cloud SDK tools to your PATH environment variable and enable command-completion in your shell, you can run:

  [PATH_TO_CLOUD_SDK]/google-cloud-sdk/install.sh
  

For more information about running the local development server including how to change the port number, see the Local Development Server reference.

OK

Make a change

You can leave the development server running while you develop your application. The development server watches for changes in your source files and reloads them if necessary.

1. Try it now: Leave the development server running, then edit main.py to change Hello, World! to something else.
2. Reload http://localhost:8080/ to see the results.

Deploy your app

To deploy your app to App Engine, run the following command from within the root directory of your application where the app.yaml file is located:

gcloud app deploy

Learn about the optional flags.

Common gcloud command flags

• Include the --version flag to specify an ID that uniquely identifies that version of your app, otherwise one is generated for you. Example: --version [YOUR_VERSION_ID]
• Include the --project flag to specify an alternate GCP project ID to what you initialized as the default in the gcloud tool. Example: --project [YOUR_PROJECT_ID]

Example:

gcloud app deploy --version pre-prod-5 --project my-sample-app

To learn more about deploying your app from the command line, see Deploying a Python App . For a list of all the command flags, see the gcloud app deploy reference.

OK

View your application

To launch your browser and view the app at http://[YOUR_PROJECT_ID].appspot.com, run the following command:

gcloud app browse

Congratulations!

You have completed this quickstart.

See the following sections for information about cleaning up after this quickstart as well as links to the possible next steps you can take with your deployed applications.

To learn more about this Hello World app, see the Hello World code review section.

Clean up

If you have enabled billing, you can delete your GCP project to avoid incurring charges. This stops billing for all the resources used within that project.

Caution: Deleting a project has the following effects:
• Everything in the project is deleted. If you used an existing project for this tutorial, when you delete it, you also delete any other work you've done in the project.
• Custom project IDs are lost. When you created this project, you might have created a custom project ID that you want to use in the future. To preserve the URLs that use the project ID, such as an appspot.com URL, delete selected resources inside the project instead of deleting the whole project.
1. In the GCP Console, go to the Projects page.

   Go to the Projects page

2. In the project list, select the project you want to delete and click Delete .
3. In the dialog, type the project ID, and then click Shut down to delete the project.

What's next

Develop a basic Flask app

Learn how to develop and deploy basic Python 2.7 applications that run on the Google App Engine Standard Environment. If you're new to Google App Engine, its related services, and in particular, using App Engine with the Python language, the Flask guide provides deeper explanations for each task than what is found in the Quickstart guide. For more information, see Getting Started with Flask on App Engine Standard Environment.

Use a custom domain

You can serve your App Engine app using your own custom domain instead of appspot.com. For more information, see Using Custom Domains and SSL.

Hello World code review

Hello World is the simplest possible App Engine app: it contains only one service, has only one version, and all of the code is located within the app's root directory. This section describes each of the app files in detail.

main.py

This Python script responds to a request with an HTTP header and the message Hello, World!.

appengine/standard/hello_world/main.py

View on GitHub

import webapp2


class MainPage(webapp2.RequestHandler):
    def get(self):
        self.response.headers['Content-Type'] = 'text/plain'
        self.response.write('Hello, World!')


app = webapp2.WSGIApplication([
    ('/', MainPage),
], debug=True)

app.yaml

The app.yaml configuration file defines several options for the app, and describes which handler scripts should be used for which URLs.

appengine/standard/hello_world/app.yaml

View on GitHub

runtime: python27
api_version: 1
threadsafe: true

handlers:
- url: /.*
  script: main.app

From top to bottom, this configuration file says the following about this application:

• This code runs in the python27 runtime environment, API version 1.
• This application is threadsafe so the same instance can handle several simultaneous requests. Threadsafe is an advanced feature and can result in erratic behavior if your application is not specifically designed to be threadsafe.
• Every request to a URL whose path matches the regular expression /.* (all URLs) should be handled by the app object in the main Python module.

The syntax of this file is YAML. For a complete list of configuration options, see the app.yaml reference.

Learn more

Learn the whole platform

Now that you know what it's like to develop and deploy App Engine apps, you can stretch out and see the rest of Google Cloud Platform. For a guided walkthrough that teaches you how to create an application that uses the entire platform, not just App Engine, check out our Creating a Guestbook quickstart in which you expand this simple application to become a fully-fledged Guestbook application that lets authenticated Google accounts post messages to a public page.

• Creating a Guestbook

Learn more about App Engine standard environment

Here are some topics to help you to continue learning about App Engine.

• An Overview Of App Engine
• Application Architecture
• Handling Requests
• Routing Requests