Flask Web Development, 2nd Edition

Chapter 7. Large Application Structure

Although having small web applications stored in a single script file can be very convenient, this approach does not scale well. As the application grows in complexity, working with a single large source file becomes problematic.

Unlike most other web frameworks, Flask does not impose a specific organization for large projects; the way to structure the application is left entirely to the developer. In this chapter, a possible way to organize a large application in packages and modules is presented. This structure will be used in the remaining examples of the book.

Project Structure

Example 7-1 shows the basic layout for a Flask application.

Example 7-1. Basic multiple-file Flask application structure

|-flasky
  |-app/
    |-templates/
    |-static/
    |-main/
      |-__init__.py
      |-errors.py
      |-forms.py
      |-views.py
    |-__init__.py
    |-email.py
    |-models.py
  |-migrations/
  |-tests/
    |-__init__.py
    |-test*.py
  |-venv/
  |-requirements.txt
  |-config.py
  |-flasky.py

This structure has four top-level folders:

• The Flask application lives inside a package generically named app.

• The migrations folder contains the database migration scripts, as before.

• Unit tests are written in a tests package.

• The venv folder contains the Python virtual environment, as before.

There are also a few new files:

• requirements.txt lists the package dependencies so that it is easy to regenerate an identical virtual environment on a different computer.

• config.py stores the configuration settings. ...