How To Create/Build Google Applications(Apps)

How to create a Pythonic app in Google App Engine

Whilst the official pythonic reference for Google app engine is the way I learnt how to build my first GAE app, I found it a bit frustrating to go through each and every link and understand large topics like caching and data stores in detail just to build a small hello world pythonic app in Google App Engine. What I wanted was a quick and dirty tutorial that let me build a small app first, and then let me improvise upon the areas that I needed to dig deep. I couldn’t find such a tutorial anywhere, so I’m writing this one.

1. Setup your Environment: Download and install python 2.7 for your platform, if you haven’t done so already (as of this writing, only 2.5 and 2.7 versions are supported) . Then, download and install the GAE API from here. MSI setups are available for windows platform. For linux, you can just unzip into a local folder like ‘~/programs/’. The zip file will create a subdir called ‘google_appengine’. Practically, the only two python scripts you are ever going to need to develop a GAE app are:
   • dev_appserver.py
   • appcfg.py
   
   
2. Register your app on appspot.com: The next step is to register your subdomain on GAE by visiting https://appengine.google.com. Once you register your app there, you will get a subdomain called http://your-app-id.appspot.com. There are also options for redirecting your custom domain such as www.mydomain.com to your app subdomain.
   
3. Create your app on the local machine: This is as simple as creating a folder on your machine such as ~/source/foo in linux or C:\source\foo in windows. Then just create a text file named app.yaml  with below contents inside this folder:

   application: your-app-id version: 1 runtime: python27 api_version: 1 threadsafe: true   handlers: - url: /.*   script: helloworld.application

   Note that your-app-id is the name that you just registered for yourself, make sure that it is typed correctly. version parameter refers to the version of your app, while api_version is the version of GAE SDK used to run this app. The line “script: helloworld.application” indicates that this wsgi handler will be invoked for your app.
   
4. Create the wsgi handler: This is as simple as creating a python file named “helloworld.py” in the same folder as above, and add below contents to it:

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

5. Test your app: To test your app, open up your terminal and change directory to your GAE installation folder (alternatively, add the GAE installation folder to your PATH/$PATH environment variable to avoid doing this each time), and then type the below command:

   python dev_appserver.py ~/source/foo
   #OR on windows:
   python dev_appserver.py C:\source\foo

6. Deploy your app: Want to host this app on GAE and check it out? Just fire up your terminal as described above and issue this command:

   python appcfg.py update ~/source/foo
   #OR on windows:
   python appcfg.py update C:\source\foo

7. Test your app: The above command should host your app on your appspot subdomain (It will ask for your google username/password before doing so). Once the app is successfully hosted, you can check it out by visiting http://your-app-id.appspot.com.
   
8. Furthur reading: Now that you have a working app, you can actually visit the official reference to read more about:
   1. webapp2: The pythonic web framework used to handle requests and generate responses.
   2. Datastore: The big data storage feature that GAE provides your app to store its data.
   3. Quotas and Limits: Learn about the various limits that google sets for your app to access resources (Don’t worry, they are enough to suffice a small to medium scale app).
   4. App caching: Learn how to take advantage of various caching mechanisms in GAE to speed up your app.

      How To Build Google Apps                                                                                                                                                                                                                                                     The Google Apps Engine allows developers to create apps in a variety of different programming languages, including the Java Runtime Environment and the Python Runtime Environment. You need a Google developer account to create apps. Each free developer account can host up to ten applications, which can be viewed up to five million times per month. While the process of developing and building an App is complicated and requires tremendous technical ability, Google provides a host of support information designed to help developers create and fine-tune their own Google apps.

      
      

      Instructions

      1. • Download and install the Google SDK from the Google App Engine downloads page. The app can be coded using the Python, Java or GO programming language. Once you have compiled and saved the app, you can complete the app building process using the Google App Engine website. While programming an app requires a high level understanding of software development, details on the nuances of the different programming languages are available in the Google App Engine's Developer's Guide.
         • 2
           Log in to the Google App Engine website using the login credentials from a Google account. You can create a free Google account on the Google Accounts website.
         • 3
           Click the "Create Application" button and verify the account by providing a cellphone number capable of receiving text messages. Once you have received the verification text message, enter the contents in the box labeled "Enter account code."
         • 4
           Complete the fields labeled "Application Identifier" and "Application Title" now displayed on the page with the identifier and title that will be used for the application. Review and accept the Terms of Service and click "Create an Application."
         • 5
           Upload the completed application to the Google App engine website by typing the following command into the Google SDK: "appcfg.py update helloworld/." When prompted, enter the username and password for the Google account you used to create the developer account to complete the app building process.