Quiz 4 Study Guide

Special Note: since we have now switched to online learning, this quiz
will be a little different from the previous paper and pencil quizzes.

For this quiz you will be given some programs to write or fix.
They will be in a certain location in your cs21 directory, on the CS
computers. You will be able to use atom to write the programs, and to
ssh to the CS computers to run them and test them. Once you have written
each program, you will run handin21 to turn them in.  You will still
have a time limit for writing the programs (probably 30 minutes), but
you will be able to "take the quiz" anytime during the week (whenever
you have time and the network is working!).

So practice for this quiz by writing the functions and programs below.
More details coming soon, but let us know if you have any questions so
far.

You are responsible for all material covered through the end of Week 8 (TDD).

In addition to all concepts from Quiz 3, you should understand the following:

Python concepts

  • using objects, data and methods of an object

  • mutability of objects

  • lists and strings as objects

  • common string methods (e.g., upper(), lower(), split(),isdigit(), isalpha())

  • adding to a list with the append() method

  • top-down design

  • bottom-up implementation

  • stubbed-out (prototyped) functions

  • list of lists

Practice problems

  1. The following isVowel(letter) function doesn’t work. For example, calling isVowel("a") returns True, but so does isVowel("b"). Find and fix the bug in isVowel(letter)

    def isVowel(letter):
    """
    letter: a single character (string)
    returns: True if given letter is a vowel, False if not
    """
    letter = letter.lower()
    if letter=="a" or "e" or "i" or "o" or "u":
        return True
    else:
        return False

  2. Given the assignments for S and L, what is the value and type of each expression?

    S = "abcdefg"
L = ['Join me', 'and we can rule', 'the galaxy', 'as father and son']

                                 VALUE            TYPE
                                 -----            ----
    len(L)
    len(L[0])
    len(S)
    "a" in L[2]
    "ABC" in S
    L[0][0]
    S.upper()
    S.isdigit()
    L[1].split()
    S < "zebra"

  3. Assume you have these two functions already written:

    • getPick() asks the user for "r,p,s?" and returns:

      • "rock" if they enter r

      • "paper" if they enter p

      • "scissors" if they enter s

    • winner(user,comp) returns:

      • "user" if user won the game (e.g., user="rock", comp="scissors")

      • "comp" if comp won the game (e.g., user="rock", comp="paper")

      • "tie" if it’s a tie game (e.g., user="rock", comp="rock")

        Write a main() function that uses the above functions to play one round of rock-paper-scissors. Here are a few sample runs of the program:

        $ python3 rps.py
r,p,s: r
I chose rock
tie...
$ python3 rps.py
r,p,s: r
I chose paper
I WIN!
$ python3 rps.py
r,p,s: r
I chose scissors
you win :(

  4. Now write and add the getPick() function to your rock-paper-scissors program. Your getPick() function should only accept r, p, or s from the user. If they enter anything else, print an error message and ask again.

    r,p,s: w
please enter r, p, or s!!!
r,p,s: zebra
please enter r, p, or s!!!
r,p,s: r

  5. Now write and add the winner(user,comp) function. Hint: check for the "tie" case first, then all cases where the user wins, leaving the "comp" case for last.