bridge.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
*References:
http://en.wikibooks.org/wiki/Computer_Science_Design_Patterns/Bridge_Pattern#Python

*TL;DR
Decouples an abstraction from its implementation.
"""


# ConcreteImplementor 1/2
class DrawingAPI1(object):
    def draw_circle(self, x, y, radius):
        print('API1.circle at {}:{} radius {}'.format(x, y, radius))


# ConcreteImplementor 2/2
class DrawingAPI2(object):
    def draw_circle(self, x, y, radius):
        print('API2.circle at {}:{} radius {}'.format(x, y, radius))


# Refined Abstraction
class CircleShape(object):
    def __init__(self, x, y, radius, drawing_api):
        self._x = x
        self._y = y
        self._radius = radius
        self._drawing_api = drawing_api

    # low-level i.e. Implementation specific
    def draw(self):
        self._drawing_api.draw_circle(self._x, self._y, self._radius)

    # high-level i.e. Abstraction specific
    def scale(self, pct):
        self._radius *= pct


def main():
    shapes = (CircleShape(1, 2, 3, DrawingAPI1()), CircleShape(5, 7, 11, DrawingAPI2()))

    for shape in shapes:
        shape.scale(2.5)
        shape.draw()


if __name__ == '__main__':
    main()

### OUTPUT ###
# API1.circle at 1:2 radius 7.5
# API2.circle at 5:7 radius 27.5