The Development Web Server

The App Engine SDK includes a web server application that simulates the App Engine Python runtime environment. The development server:

• reproduces the module import restrictions, and only allows handlers to import an allowed module from the standard library, the third-party libraries included in the App Engine Python environment, and modules in the application directory
• reproduces the app caching behavior
• emulates the App Engine datastore using local files
• emulates Google Accounts with sign-in and sign-out pages that accept any email address
• emulates the URL fetch service by fetching URLs directly from your computer
• emulates the mail service using an SMTP server or Sendmail configuration of your choice

Note that dev_appserver.py does not emulate quotas or limits such as request time-outs.

Be sure to run dev_appserver.py using Python 2.5. It will run under Python 2.4, but there are differences between Python 2.4 and 2.5 that may affect your application, such as handling of Unicode strings.

For more information, see The Development Web Server.