Lab?7 –?CPS?106

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This lab helps you get familiar with classes and inheritance.

1. ??Write?a?class?called?Shape.

class Shape:

2. ??The Shape class is?going to?represent?a?general?shape?in?the?2D?plane.?A?shape?is?described?by?a set of?points that determine its boundary. Write?a?class?called Point. The?point?class?has?two?attributes?x?and?y?which?are?unique?to?each?point.?So?we?define?them?as?instance?variables,?i.e., using the self?object. We initialize them in the __init__ mathod.

class Point(x,?y):

def __init__(self, x, y):

self.x?=?x

self.y?=?y

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3. ??Write ?the?__str__?method?for?the?Point?class.?The?method ?should?return?a ?string?in?the?following format: “(x, y)”

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4. ??Test the point class using the following:

p?=?Point(31,?7)

print(p)

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5. ??Add?the?__init__?method?to?the?shape?class.?In?the?method?you?should?initialize?the?list?of?boundary points to empty:

self.boundary =?[]

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6. ??Add a method called?set_boundary?to the?Shape?class.?The?set?boundary?method?accepts?a?list?of?points called boundary. In the method you should set self.boundary to the input boundary:

def set_boundary(boundary):

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7. ??Write?the?__str__?method?for?Shape.?The?method?should?return?a?string?in?the?following?format:?“Boundary: (x1, y1), (x2, y2),?...” where the?set of?points?are?the?ones?in?self.boundary.?Hint1:?remember?that?the?point?class?gives?you?a?string?of the?form?“(x,?y)”,?so?you?can?use?that here. For?example?if self.boundary[0]?is?the point p?=?(5,?12)?then?str(p)?is?the?string?“(5,

12)”. Hint2: you should loop through all the points in self.boundary to get the final?result.

8. ??Define a class called Rectangle.?The?Rectangle?class?will?be?a?subclass?of?Shape:

class Rectangle(Shape):

pass

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9. ??Test?the?rectangle?class?using?the?following.?The?first?point?is?assumed?to?be?the?bottom?left?corner of?the rectangle.

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rect =?Rectangle()

rect.set_boundary([Point(0, 0), Point(0, 3), Point(5,?3),?Point(5,?0)])

print(rect)

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10.?Define a class called Square. The Square?class will be?a?subclass?of?Rectangle:

class Square(Rectangle):

pass

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Test?the?Square?class?using?the?following.?The?first?point?is?assumed?to?be?the?bottom?left?corner of?the square.

square =?Square()

square.set_boundary([Point(0, 0), Point(0, 3), Point(3,?3),?Point(3, 0)])

print(square)

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11.?Define a class called Triangle. The Triangle class will be?a?subclass?of?Shape.?Test?the Triangle?class using the following:

trgle =?Triangle()

p(t)ri(rg)t(e)tgle(set_)oundary([Point(0, 7), Point(3, 3),?Point(2,?5)])

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12.?The diagram of?the classes now looks like the following:

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13.?Add the following method to the Square class:

def set_side_length(length):

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The argument length is an integer, based on which the new boundary?point?of?the?square?will?be?calculated.?Since?the?first?point,?i.e.,?p?=?self.boundary[0],?is?the?bottom?left?corner,?the?point?above p, i.e.,?self.boundary[1], will be?(p.x,?p.y?+?length).?Figure?out?the?position?of the?rest of?the points. Test your code using the following:

square.set_side_length(5)

print(square)

代碼

7-1

7-2

7-13 class