Quiz 3 Study Guide

You are responsible for all material needed for Lab 5.

Study guides are not graded. You may work with other students on the questions, and ask questions about the guide during evening ninja help sessions, or with meetings with faculty and staff. We do not provide full solutions to the study guides.

The study guide is not indicative of length, difficulty, or format of the quiz.

In addition to all concepts from Quiz 2, you should understand the following:

functions and stack diagrams for functions that take basic types as parameters(int, float, bool, string).
list data type
list operations and manipulation (len, indexing, append, etc)
accumulating lists using append
passing lists to functions, and stack diagrams for functions that take lists as parameters
functions that return values (basic types or lists) and functions with side effects (e.g., those that print or that modify a list that is passed as an argument)

Sample practice problems

Write a function called get_number(lo, hi) that takes two integer arguments, lo and hi, and returns an integer value between lo and hi (inclusive). The function should repeatedly ask the user for a number until the user enters a number in the correct range. Write a main() function uses your get_number function to get a number between 1 and 10 from the user. The program should then print the number the user entered. A sample run of the program is shown below with user input in bold:
```
Enter a number between 1 and 10: -1
This number is out of range. Please try again
Enter a number between 1 and 10: 22
This number is out of range. Please try again
Enter a number between 1 and 10: 7
You picked: 7
```
What would you need to change in your program above to get a number between 2 and 13 instead?
Analyze the following code:
```
m = ["t","i","m","e"]
s = "time"
m[1] = "a"
print(m)
s[1] = "a"
print(s)
```
What happens when this code is executed? What, if any, output is shown?

Consider the following program:

def main():

    print("in main")
    n = 3
    m = 5
    z = mystery(n, m)
    print("n = %d" % n)
    print("m = %d" % m)
    print("z = %d" % z)

def mystery(a, b):

    print("in mystery")
    result = b
    if a < b:
        result = a  + b
        b = b - 1

    # draw stack here
    print("a = %d" % a)
    print("b = %d" % b)
    return result

main()

Draw the function stack as it would look before the call to mystery() returns.
Show the output of the program when it is run.

Consider the following program:

def main():

   values = [5,3,4,8]
   print(values)
   result = enigma(values)
   print("result: %d" % result)
   print(values)

def enigma(ls):
   total = 0
   val = len(ls)
   for i in range(len(ls)):
      if (ls[i] > val):
         ls[i] = ls[i]*2
      total = total + ls[i]
   # Q1: draw the stack at this point in the exection
   return total

main()

Draw the function stack as it would look right before enigma returns.
What variables are in scope at this point in the code?
What is the program’s output (i.e. what does it print when the program is run)?
What does the enigma() function do?

The following get_numbers(n) function doesn’t work correctly. Find and fix the bug in the code below.

def get_numbers(n):
    """
    Purpose: Read n numbers from the user and return them as a list
    Parameters: n -- the number of values to read from the user (integer)
    Return: a list of the numbers entered by the user
    """
    for i in range(n):
        value_list = []
        value = int(input("Enter a number: "))
        value_list.append(value)
    return value_list

Consider the following assignment statements in a Python program:
```
letters = "abacab"
words = ["we hope", "you have", "a nice", "Spring Break"]
vals = [9, 11, 100, 20, 6]
text = words[0]
```
For each of the following, identify the type and value of the expression:
1. len(letters)
2. len(words)
3. len(vals)
4. len(words[2])
5. letters[1]
6. words[1]
7. vals[1]
8. vals[4] > len(letters)
9. letters > words[1]
10. text[1]
11. vals[1] // 2
12. vals[1] / 2
13. vals[1] % 2
14. vals
15. words