Introduction to Computer Science II

Winter 2022 Midterm Practice Exam

Solve the below problems by implementing the appropriate classes and methods in file midtermPractice.py.

Problems

1. [30pts] Write a class named Vehicle that can be used as shown below:

Usage:
>>> v = Vehicle() >>> v.add_cargo('train')>>> v.add_cargo('ball')>>> v.add_cargo('doll')>>> v.cargo_contents() ['train', 'ball', 'doll']>>> v.deliver() 'doll'>>> v.cargo_contents() ['train', 'ball']

Note: you will need to implement an __init__ constructor in addition to methods add_cargo, cargo_contents, and deliver. Method deliver should remove and return the last item added to the cargo (i.e., last in, first out).

2. [30 pts] Write a class named Sled as a subclass of Vehicle that inherits all the attributes of Vehicle and also:

extends the Vehicle __init__ constructor to take, as input, the coordinates x and y of the Vehicle object,
supports method move that takes number values dx and dy as input and moves the sled by dx units along the x-axis and by dy units along the y-axis, and
overloads the __str__ operator so it behaves as shown below.

Usage:
>>> s = Sled(0,0)
>>> s.add_cargo('train')
>>> s.add_cargo('ball')
>>> s.cargo_contents()
['train', 'ball']
>>> s.move(2,1)
>>> s.deliver()
'ball'
>>> print(s)
Gifts being delivered at location (2,1)
>>> s.move(3,7)
>>> s.deliver()
'train'
>>> print(s)
Gifts being delivered at location (5,8)

3. [30 points] Implement a GUI widget class Calculator that consists of an Entry widget and a Button widget labeled "Compute":

To use the app, the user should enter an arithmetic expression in the Entry:

When the user clicks on the Button, a popup window should display the result:

After the user clicks OK in the popup window, the Entry should be empty and ready for the next expression (as shown in the first image).

Usage:
>>> Calculator().pack()

4. [10 points] Implement a GUI widget class App that consists of the Calculator widget your just implemented and the Draw widget covered in class (and already included in the midtermPractice.py file):

Usage:
>>> App().pack()