Solution Manual for Starting Out with Python, Global Edition, 4th Edition

Chapter 2 Multiple Choice 1. c 2. b 3. d 4. b 5. a 6. c 7. a 8. b 9. d 10. a 11. b 12. d 13. b 14. a 15. a 16. c 17. a 18. b 19. a 20. b 21. b 22. b True or False 1. False 2. True 3. False 4. True 5. False Short Answer 1 Interview the customer 2. Pseudocode, an informal language with no syntax rules, is intended to establish and communicate the design of a program. Actual code must adhere to the syntax of the language it is written in, and is used to implement a program. 3. (1) Input is received. (2) Some process is performed on the input. (3) Output is produced. 4. Variable names must adhere to the naming rules of the language, such as not being a key word of the language, beginning with a letter, and not containing a space. Variable names should preferably reflect the nature of the data that they reference to make the variable’s purpose clear. 5. Floating point division returns a floating point number that may include fractions. Integer division returns an integer and ignores any fractional part of the division result. 6. A magic number is an unexplained value that appears in a program’s code. Magic numbers can be problematic, for a number of reasons. First, it can be difficult for someone reading the code to determine the purpose of the number. Second, if the magic number is used in multiple places in the program, it can take painstaking effort to change the number in each location, should the need arise. Third, you take the risk of making a typographical mistake each time you type the magic number in the program’s code. 7. The named constant makes the program more self-explanatory. In a math statement, it is evident that PI represents the value of pi. Another advantage to using the named constant is that widespread changes can easily be made to the program. Let’s say the value of pi appears in several different statements throughout the program. If you need to change the number of decimal places of precision used with the number, the initialization value in the declaration of the named constant is the only value that needs to be modified. For example, to use only two decimal places of precision, the declaration can be changed to: PI = 3.14 The new value of 3.14 will then be used in each statement that includes the PI constant. Another advantage to using the named constant is that it helps to prevent the typographical errors that are common when using magic numbers. For example, if you accidentally type 31.4159 instead of 3.14159 in a math statement, the program will calculate the wrong value. However, if you misspell PI, the Python interpreter will display a message indicating that the name is not defined. Algorithm Workbench 1. age = int(input(‘Enter your age: ‘)) 2. color = input(‘Enter your favorite color: ‘) 3. a. b. c. d. b = a + 2 a = b * 4 b = a / 3.14 a = b – 8 4. a. b. c. d. 12 4 2 6 e. 2 5. product = 10 * 15 6. due = total – down_payment 7. total = subtotal * 0.15 8. 11 9. 5 10. print(format(sales, ‘.2f)) 11. print(format(number, ‘,.1f’)) 12. $X O X O X O X O X $ 13. turtle.circle(75) 14. turtle.fillcolor(‘blue’) turtle.begin_fill() turtle.forward(100) turtle.left(90) turtle.forward(100) turtle.left(90) turtle.forward(100) turtle.left(90) turtle.forward(100) turtle.end_fill() 15. turtle.forward(100) turtle.left(90) turtle.forward(100) turtle.left(90) turtle.forward(100) turtle.left(90) turtle.forward(100) turtle.penup() turtle.left(90) turtle.forward(50) turtle.right(90) turtle.forward(30) turtle.setheading(0) turtle.pendown() turtle.fillcolor(‘red’) turtle.begin_fill() turtle.circle(80) turtle.end_fill()