IT 212 -- Sep 23, 2020 Notes

IT 212 -- Sep 23, 2020

Review Exercises

Zoom Poll 4: Review Exercises:
1. The bool method converts a value to boolean (True or False). The rule is that zero converts to False, but everything else converts to True. The null string "" is considered to be "zero" or False for the bool method. Every other string, including "False" is considered to be non-zero. What is the value of this expression?
```
bool(0)
a. True    *b. False
```
2. What is the value of this expression?
```
bool(961)
*a. True    b. False
```
3. What is the value of this expression?
```
bool(961)
*a. True    b. False
```
4. What is the value of this expression?
```
bool(961)
*a. True    b. False
```
5. What is the value of this expression?
```
bool(961)
*a. True    b. False
```
6. What is the value of this expression?
```
bool("orange")
*a. True    b. False
```
7. What is the value of this expression?
```
bool("False")
*a. True    b. False
```
8. What is the value of this expression?
```
bool("")
a. True    *b. False
```
9. What is the value of this expression?
```
bool(0.0000001)
*a. True    b. False
```
10. What is the value of this expression?
```
bool(0.0000001)
*a. True    b. False
```
11. What is the value of this expression?
```
bool(0.0)
a. True    *b. False
```
12. What is the value of this expression?
```
int(bool(3482))
a. 0    *b. 1    c. 3482
```
Identify the arguments and the parameters:
```
# --------------------------
# Module name: my_method1.py
def square(n):
    return n ** 2
    
# -------------------------
# Module name: main.py
import my_method1
print(my_method1.square(7))
# ------------------------
```
Ans: Arguments are values passed in to a method when it is called. Parameters are variables passed in to a method when it is defined with a def statement. The parameters tell the method what to do with the arguments.

n is the parameter for the square method, 7 is the argument for the square method, and my_method1.square(7) is the argument for the print method.

Identify the arguments, parameters, and local variables:

# ---------------------
# Module: my_method2.py
def sum_array(the_array):
    total = 0
    for n in the_array:
        total += n
    return total

# --------------------
# Module: main.py
from my_method2 import sum_array
a = [1, 2, 3, 4]
print(sum_array(a))
# --------------------

Ans: the_array is the parameter for the sum_array method. a is the argument for the sum_array method in main; sum_array(a) is the argument of the print method. total and n are local variables in main.

Look at Problem 5 from extract-methods.zip
Ans:extract-methods-ans.zip.
Give an example of a list of lists. A list of lists is also called a ragged array.
Look at Problem 6 from extract-methods.zip
Ans:extract-methods-ans.zip.
The ragged array defined by game3.txt records the number of bowling pins knocked down by each ball. Compute the score for the game. The score for the game is the number of pins knocked down plus bonuses for spares and strikes. The bonus for a spare is the number of pins knocked down by the next ball; the bonus for a strike is the number of pins knocked down by the next two balls.
Ans: Here are the calculations for the input file game3.txt.

Project 2

See the Project 2 Description for the details of bowling rules and scoring.

Here is a list of lists (also called a ragged array) that shows the pins knocked down in a bowling game:

["Frame0", [7, 2], [8, 2], [10], [10], [10], 
    [10], [10], [9, 1], [10], [10], [7, 3]]

"Frame0" is prepended to the array as a placeholder for Frame 0, which is not actually a frame in a bowling game. This is so the index of the first frame [7, 2] is 1. What is the score for each frame? Ans:

Frame Number	Frame as List	Frame Score
1	[7, 2]	9
2	[8, 2]	8 + 2 + 10 = 20
3	[10]	10 + 10 + 10 = 30
4	[10]	10 + 10 + 10 = 30
5	[10]	10 + 10 + 10 = 30
6	[10]	10 + 10 + 9 = 29
7	[10]	10 + 9 + 1 = 20
8	[9, 1]	9 + 1 + 10 = 20
9	[10]	10 + 10 + 7 = 27
10	[10]	10 + 7 + 3 = 20
Bonus	[7, 3]

The score for the entire game is the sum of all the frame scores, which is 235.

Here is the frame_score method with the first two cases of strike and spare:

def frame_score(the_frame, next_ball_1, next_ball_2):

    # Case of a strike
    if the_frame[0] == 10:
        return 10 + next_ball_1 + next_ball_2

    # Case of a spare
    elif the_frame[0] + the_frame[1] == 10:
        return 10 + next_ball_1

You add the third case of an open frame.

Introduction to Classes

A class contains instance variables (that contain data) and methods (that are procedures for doing something).
A class can create objects. The number of objects that can be created is only limited by the computer's available. A fancy name for creating an object is instantiating (creating an instance of) an object.
Look at the Person Example.
A UML diagram is a summary of the instance variables and methods for a class. It contains three sections: the class name, the instance variables, and the methods.
Here is UML diagram for the Person class.
The __init__ and __str__ methods receive special treatment from the Python compiler. They are called dunder methods or magic methods. Dunder means double underscore prefix and postfix.
Give some plausible instance variables and methods for a BasketballPlayer class.:
Instance variables: name jersey_number height weight age isRookie
Instance methods: shoot pass run dribble block dunk foul stop