15.6. Exercises — How to Think like a Computer Scientist: Interactive Edition

We can represent a rectangle by knowing three things: the location of its lower left corner, its width, and its height. Create a class definition for a Rectangle class using this idea. To create a Rectangle object at location (4,5) with width 6 and height 5, we would do the following:
r = Rectangle(Point(4, 5), 6, 5)
class Point: """ Point class for representing and manipulating x,y coordinates. """ def __init__(self, initX, initY): self.x = initX self.y = initY def getX(self): return self.x def getY(self): return self.y def __str__(self): return "x=" + str(self.x) + ", y=" + str(self.y) class Rectangle: """Rectangle class using Point, width and height""" def __init__(self, initP, initW, initH): self.location = initP self.width = initW self.height = initH loc = Point(4, 5) r = Rectangle(loc, 6, 5) print(r)
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Add the following accessor methods to the Rectangle class: getWidth, getHeight, __str__.

Add a method area to the Rectangle class that returns the area of any instance:
r = Rectangle(Point(0, 0), 10, 5) test(r.area(), 50)
class Point: """ Point class for representing and manipulating x,y coordinates. """ def __init__(self, initX, initY): self.x = initX self.y = initY def getX(self): return self.x def getY(self): return self.y def __str__(self): return "x=" + str(self.x) + ", y=" + str(self.y) class Rectangle: """Rectangle class using Point, width and height""" def __init__(self, initP, initW, initH): self.location = initP self.width = initW self.height = initH def area(self): return self.width * self.height
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Write a perimeter method in the Rectangle class so that we can find the perimeter of any rectangle instance:
```
r = Rectangle(Point(0, 0), 10, 5)
test(r.perimeter(), 30)
```

Write a transpose method in the Rectangle class that swaps the width and the height of any rectangle instance:
r = Rectangle(Point(100, 50), 10, 5) test(r.width, 10) test(r.height, 5) r.transpose() test(r.width, 5) test(r.height, 10)
class Point: """ Point class for representing and manipulating x,y coordinates. """ def __init__(self, initX, initY): self.x = initX self.y = initY def getX(self): return self.x def getY(self): return self.y def __str__(self): return "x=" + str(self.x) + ", y=" + str(self.y) class Rectangle: """Rectangle class using Point, width and height""" def __init__(self, initP, initW, initH): self.location = initP self.width = initW self.height = initH def transpose(self): temp = self.width self.width = self.height self.height = temp
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Write a new method called diagonal that will return the length of the diagonal that runs from the lower left corner to the opposite corner.

class Point: """ Point class for representing and manipulating x,y coordinates. """ def __init__(self, initX, initY): self.x = initX self.y = initY def getX(self): return self.x def getY(self): return self.y def __str__(self): return "x=" + str(self.x) + ", y=" + str(self.y) class Rectangle: """Rectangle class using Point, width and height""" def __init__(self, initP, initW, initH): self.location = initP self.width = initW self.height = initH def diagonal(self): d = (self.width**2 + self.height**2) ** 0.5 return d
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In games, we often put a rectangular “bounding box” around our sprites in the game. We can then do collision detection between, say, bombs and spaceships, by comparing whether their rectangles overlap anywhere.

Write a function to determine whether two rectangles collide. Hint: this might be quite a tough exercise! Think carefully about all the cases before you code.

15.6. Exercises¶