CSC111 Top-Down Rock-Paper-Scissors

--D. Thiebaut (talk) 19:15, 5 March 2014 (EST)

---

Starting Point

This is the very first "draft". It won't compile, but it contains the logic of the game.

# rock, paper, scissors
# D. Thiebaut
# A top-down approach

HUMAN    = "H"
COMPUTER = "C"

def main():
    # counters for winning rounds
    humanCount    = 0
    computerCount = 0

    # play rounds
    while ( abs( humanCount - computerCount ) < 3 ):
        # play one round between computer and human
        winner = playRound()

        # see if human wins
        if winner == HUMAN:
            humanCount += 1

        # see if computer wins
        if winner == COMPUTER:
            computerCount += 1

        # if neither, it's a tie and we don't increment
        # counters at all

    # loop is over. We announce the winner
    printOutcome( humanCount, computerCount )

main()

Step 2

We add empty functions to allow the interpreter to parse our program. Note that the functions do not do anything, just the bare minimum of what they are supposed to do.

# rock, paper, scissors
# D. Thiebaut
# A top-down approach

HUMAN    = "H"
COMPUTER = "C"

# playRound: plays a round between human and computer.
# returns the winner of the round (HUMAN or COMPUTER)
def playRound():
    print( "round" )
    return HUMAN

# printOutcome: displays the winner of the game 
def printOutcome( humanCount, computerCount ):
    print( humanCount, computerCount )
    
def main():
    # counters for winning rounds
    humanCount    = 0
    computerCount = 0

    # play rounds
    while ( abs( humanCount - computerCount ) < 3 ):
        # play one round between computer and human
        winner = playRound()

        # see if human wins
        if winner == HUMAN:
            humanCount += 1

        # see if computer wins
        if winner == COMPUTER:
            computerCount += 1

        # if neither, it's a tie and we don't increment
        # counters at all

    # loop is over. We announce the winner
    printOutcome( humanCount, computerCount )

main()

Output of the program

>>>
Round
Round
Round
3 0
>>> 

Step 3

We take one of the functions, the simplest one to expand, and do so. Here, it's printOutcome() that we work on.

# rock, paper, scissors
# D. Thiebaut
# A top-down approach

HUMAN    = "H"
COMPUTER = "C"

# playRound: plays a round between human and computer.
# returns the winner of the round (HUMAN or COMPUTER)
def playRound():
    print( "Round" )
    return HUMAN

# printOutcome: displays the winner of the game 
def printOutcome( humanCount, computerCount ):
    if humanCountn > computerCount:
        print( "You win!" )
    else:
        print( "I win!" )
    
def main():
    # counters for winning rounds
    humanCount    = 0
    computerCount = 0

    # play rounds
    while ( abs( humanCount - computerCount ) < 3 ):
        # play one round between computer and human
        winner = playRound()

        # see if human wins
        if winner == HUMAN:
            humanCount += 1

        # see if computer wins
        if winner == COMPUTER:
            computerCount += 1

        # if neither, it's a tie and we don't increment
        # counters at all

    # loop is over. We announce the winner
    printOutcome( humanCount, computerCount )

main()

# rock, paper, scissors
# D. Thiebaut
# A top-down approach

from random import seed
from random import choice
seed()

HUMAN    = "H"
COMPUTER = "C"
TIE      = "T"

# pickAletter: lets user pick a letter that is 'R', 'S', or 'P'
# and keeps on prompting until the letter is correctly entered.
def pickALetter():
    answer = " "
    while answer != "P" and answer != "S" and answer != "R":
        answer = input( "> " ).upper().strip()
        
    return answer

# pickRandom: picks a random letter in 'R', 'S', 'P'.
def pickRandom():
    OPTIONS = [ 'R', 'S', 'P' ]
    answer = choice( OPTIONS )
    #print( "Computer picked:" , answer )
    return answer

# playRound: plays a round between computer and human.  Human
# picks a letter, computer picks a letter at random.
# displays outcome of the game.  Returns winner
def playRound():
    computer = pickRandom()
    human    = pickALetter()

    # tell the user what the computer picked
    print( "I had picked", computer, end=": " )
    
    # checks for ties
    if human==computer:
        print( "It's a tie!" )
        return TIE

    # look at conditions where computer wins
    if (human=="P" and computer=="S")  \
    or (human=="R" and computer=="P")  \
    or (human=="S" and computer=="R"):
        print( "I win this round" )
        return COMPUTER

    # human must have won
    print( "You win this round!" )
    return HUMAN

        
# printOutcome: gets the count of rounds won by two users, and
# displays winner.
def printOutcome( humanCount, computerCount ):
    if humanCount > computerCount:
        print( "You win!" )
    else:
        print( "I win!" )    


def greetings():
    print( "Welcome to Rock-Scissors-Paper!" )
    print( "-------------------------------" )
    
# main: plays several rounds of the rock-paper-scissors game
# until one player gets 3 more points than the other.  Then
# displays the winner.
def main():
    # greets the user, displays the rules
    greetings()
    
    # counters for winning rounds
    humanCount    = 0
    computerCount = 0

    while ( abs( humanCount - computerCount ) < 3 ):
        winner = playRound()
        if winner == HUMAN:
            humanCount += 1
        if winner == COMPUTER:
            computerCount += 1
        
    
    printOutcome( humanCount, computerCount )


main()