python-patterns/patterns/structural/bridge.py at master · tlaos2/python-patterns

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*References:
http://en.wikibooks.org/wiki/Computer_Science_Design_Patterns/Bridge_Pattern#Python
Decouples an abstraction from its implementation.
# ConcreteImplementor 1/2
class DrawingAPI1:
    def draw_circle(self, x, y, radius):
        print(f"API1.circle at {x}:{y} radius {radius}")
# ConcreteImplementor 2/2
class DrawingAPI2:
    def draw_circle(self, x, y, radius):
        print(f"API2.circle at {x}:{y} radius {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()

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