pallets / flask

The Python micro framework for building web applications.

68.0k

Python

Architecture: library

View Original Source

main

flask

src

flask

__init__.py

app.py

blueprints.py

cli.py

templating.py

json

tests

test_basic.py

templates

examples

tutorial

celery

docs

CHANGES.rst

pyproject.toml

Structural Architecture

Flask is a compact, deliberately unopinionated library that uses the src layout, keeping the importable package isolated from the repository root. The framework itself is a small number of focused modules, with most extensibility pushed out to the surrounding Pallets ecosystem rather than absorbed into the core.

src layout, so tests exercise the installed package rather than the working directory.
A deliberately small core, with functionality delegated to separate Pallets projects such as Werkzeug and Jinja.
Runnable examples kept in the repository as living documentation.

Notable Directories

/src/flask

The framework itself: application object, routing, request and response handling, and templating integration.

/tests

The pytest suite, mirroring the module layout of the package it covers.

/examples

Complete small applications used both as documentation and as integration tests.

/docs

Sphinx documentation source, versioned alongside the code it documents.

Build Your Own Ecosystem

Learn from flask's structure and craft your own software scaffolding.