python-decorators

Examples

Registering an item

Decorators can be used to register an item without changing it.

def route(self, rule, **options):
    """A decorator that is used to register a view function for a
    given URL rule.  This does the same thing as :meth:`add_url_rule`
    but is intended for decorator usage::

        @app.route('/')
        def index():
            return 'Hello World'

    For more information refer to :ref:`url-route-registrations`.

    :param rule: the URL rule as string
    :param endpoint: the endpoint for the registered URL rule.  Flask
                     itself assumes the name of the view function as
                     endpoint
    :param options: the options to be forwarded to the underlying
                    :class:`~werkzeug.routing.Rule` object.  A change
                    to Werkzeug is handling of method options.  methods
                    is a list of methods this rule should be limited
                    to (``GET``, ``POST`` etc.).  By default a rule
                    just listens for ``GET`` (and implicitly ``HEAD``).
                    Starting with Flask 0.6, ``OPTIONS`` is implicitly
                    added and handled by the standard request handling.
    """
    def decorator(f):
        endpoint = options.pop('endpoint', None)
        self.add_url_rule(rule, endpoint, f, **options)
        return f
    return decorator

from flask import Flask

app = Flask('app')

@app.route('/')
def index():
    return "Hello, world!"

As can be seen in the definition of route, using this decorator does not change the function itself, so we may (if we want to) still use it as a regular function:

def test():
    print(index())

When using decorators in this way, it is important to import all modules that include a registry, if your code is broken down into multiple files.

(Script available)

# app.py
from flask import Flask

app = Flask('app')

# api.py
from app import app

@app.route('/api/')
def api_root():
    return "This api contains ..."

# main.py
from app import app
import api  # try removing this line and then visit /api

@app.route('/')
def index():
    return '<a href="/api">api</a>'

if __name__ == '__main__':
    app.run()

Prev / Up / Next