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"""

*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:

def draw_circle(self, x, y, radius):

print('API1.circle at {}:{} radius {}'.format(x, y, radius))

# ConcreteImplementor 2/2

class DrawingAPI2:

def draw_circle(self, x, y, radius):

print('API2.circle at {}:{} radius {}'.format(x, y, radius))

# Refined Abstraction

class CircleShape:

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()

API1.circle at 1:2 radius 7.5

API2.circle at 5:7 radius 27.5

"""

if __name__ == '__main__':

import doctest

doctest.testmod()