15.6. Exercises¶

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)

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(classes_deeper_q1)
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class Point:
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""" Point class for representing and manipulating x,y coordinates. """
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def __init__(self, initX, initY):
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self.x = initX
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self.y = initY
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def getX(self):
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return self.x
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def getY(self):
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return self.y
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def __str__(self):
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return "x=" + str(self.x) + ", y=" + str(self.y)
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class Rectangle:
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"""Rectangle class using Point, width and height"""
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def __init__(self, initP, initW, initH):
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self.location = initP
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self.width = initW
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self.height = initH
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loc = Point(4, 5)
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r = Rectangle(loc, 6, 5)
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print(r)
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(ch_cl2_answer1)
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Add the following accessor methods to the Rectangle class: getWidth, getHeight, __str__.
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(ch_cl2_q2)

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)

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(classes_q3)
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class Point:
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""" Point class for representing and manipulating x,y coordinates. """
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def __init__(self, initX, initY):
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self.x = initX
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self.y = initY
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def getX(self):
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return self.x
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def getY(self):
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return self.y
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def __str__(self):
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return "x=" + str(self.x) + ", y=" + str(self.y)
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class Rectangle:
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"""Rectangle class using Point, width and height"""
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def __init__(self, initP, initW, initH):
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self.location = initP
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self.width = initW
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self.height = initH
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def area(self):
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return self.width * self.height
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(ch_cl2_q3answer)
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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)
```
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(ch_cl2_q4)

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)

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(classes_q5)
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class Point:
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""" Point class for representing and manipulating x,y coordinates. """
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def __init__(self, initX, initY):
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self.x = initX
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self.y = initY
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def getX(self):
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return self.x
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def getY(self):
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return self.y
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def __str__(self):
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return "x=" + str(self.x) + ", y=" + str(self.y)
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class Rectangle:
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"""Rectangle class using Point, width and height"""
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def __init__(self, initP, initW, initH):
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self.location = initP
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self.width = initW
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self.height = initH
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def transpose(self):
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temp = self.width
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self.width = self.height
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self.height = temp
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(ch_cl2_q5answer)
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Write a new method in the Rectangle class to test if a Point falls within the rectangle. For this exercise, assume that a rectangle at (0,0) with width 10 and height 5 has open upper bounds on the width and height, i.e. it stretches in the x direction from [0 to 10), where 0 is included but 10 is excluded, and from [0 to 5) in the y direction. So it does not contain the point (10, 2). These tests should pass:
```
r = Rectangle(Point(0, 0), 10, 5)
test(r.contains(Point(0, 0)), True)
test(r.contains(Point(3, 3)), True)
test(r.contains(Point(3, 7)), False)
test(r.contains(Point(3, 5)), False)
test(r.contains(Point(3, 4.99999)), True)
test(r.contains(Point(-3, -3)), False)
```
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(classes_q6)

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.

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(classes_q7)
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class Point:
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""" Point class for representing and manipulating x,y coordinates. """
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def __init__(self, initX, initY):
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self.x = initX
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self.y = initY
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def getX(self):
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return self.x
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def getY(self):
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return self.y
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def __str__(self):
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return "x=" + str(self.x) + ", y=" + str(self.y)
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class Rectangle:
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"""Rectangle class using Point, width and height"""
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def __init__(self, initP, initW, initH):
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self.location = initP
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self.width = initW
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self.height = initH
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def diagonal(self):
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d = (self.width**2 + self.height**2) ** 0.5
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return d
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(ch_cl2_answer7)
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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.
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(ch_cl2_q8)