An Introduction to Interactive Programming in Python (Part 1) -- Week 2

An Introduction to Interactive Programming in Python (Part 1) -- Week 2_3 练习

Mini-project description - Rock-paper-scissors-lizard-Spock

Rock-paper-scissors is a hand game that is played by two people. The players count to three in unison and simultaneously "throw” one of three hand signals that correspond to rock, paper or scissors. The winner is determined by the rules:

Rock smashes scissors
Scissors cuts paper
Paper covers rock

Rock-paper-scissors is a surprisingly popular game that many people play seriously (see the Wikipedia article for details). Due to the fact that a tie happens around 1/3 of the time, several variants of Rock-Paper-Scissors exist that include more choices to make ties less likely.

Rock-paper-scissors-lizard-Spock (RPSLS) is a variant of Rock-paper-scissors that allows five choices. Each choice wins against two other choices, loses against two other choices and ties against itself. Much of RPSLS's popularity is that it has been featured in 3 episodes of the TV series "The Big Bang Theory". The Wikipedia entry for RPSLS gives the complete description of the details of the game.

In our first mini-project, we will build a Python function rpsls(name) that takes as input the string name, which is one of "rock", "paper", "scissors", "lizard", or "Spock". The function then simulates playing a round of Rock-paper-scissors-lizard-Spock by generating its own random choice from these alternatives and then determining the winner using a simple rule that we will next describe.

While Rock-paper-scissor-lizard-Spock has a set of ten rules that logically determine who wins a round of RPSLS, coding up these rules would require a large number ((5*5=25)) of if/elif/else clauses in your mini-project code. A simpler method for determining the winner is to assign each of the five choices a number:

0 — rock
1 — Spock
2 — paper
3 — lizard
4 — scissors

In this expanded list, each choice wins against the preceding two choices and loses against the following two choices (if rock and scissors are thought of as being adjacent using modular arithmetic).

In all of the mini-projects for this class, we will provide a walk through of the steps involved in building your project to aid its development. A template for your mini-project is available here. Please work from this template.

Mini-project development process

Build a helper function name_to_number(name) that converts the string name into a number between 0 and 4 as described above. This function should use a sequence of if/elif/else clauses. You can use conditions of the form name == 'paper', etc. to distinguish the cases. To make debugging your code easier, we suggest including a final else clause that catches cases when name does not match any of the five correct input strings and prints an appropriate error message. You can test your implementation of name_to_number() using this name_to_number testing template. (Also available in the Code Clinic tips thread).
Next, you should build a second helper function number_to_name(number) that converts a number in the range 0 to 4 into its corresponding name as a string. Again, we suggest including a final else clause that catches cases when number is not in the correct range. You can test your implementation of number_to_name() using this number_to_name testing template.
Implement the first part of the main function rpsls(player_choice). Print out a blank line (to separate consecutive games) followed by a line with an appropriate message describing the player's choice. Then compute the number player_number between 0 and 4 corresponding to the player's choice by calling the helper function name_to_number() using player_choice.
Implement the second part of rpsls() that generates the computer's guess and prints out an appropriate message for that guess. In particular, compute a random number comp_number between 0 and 4 that corresponds to the computer's guess using the function random.randrange(). We suggest experimenting with randrange in a separate CodeSkulptor window before deciding on how to call it to make sure that you do not accidently generate numbers in the wrong range. Then compute the name comp_choice corresponding to the computer's number using the function number_to_name() and print an appropriate message with the computer's choice to the console.
Implement the last part of rpsls() that determines and prints out the winner. Specifically, compute the difference between comp_number and player_number taken modulo five. Then write an if/elif/else statement whose conditions test the various possible values of this difference and then prints an appropriate message concerning the winner. If you have trouble deriving the conditions for the clauses of this if/elif/else statement, we suggest reviewing the "RPSLS" video which describes a simple test for determine the winner of RPSLS.

This will be the only mini-project in the class that is not an interactive game. Since we have not yet learned enough to allow you to play the game interactively, you will simply call your rpsls function repeatedly in the program with different player choices. You will see that we have provided five such calls at the bottom of the template. Running your program repeatedly should generate different computer guesses and different winners each time. While you are testing, feel free to modify those calls, but make sure they are restored when you hand in your mini-project, as your peer assessors will expect them to be there.

The output of running your program should have the following form:

Player chooses rock
Computer chooses scissors
Player wins!

Player chooses Spock
Computer chooses lizard
Computer wins!

Player chooses paper
Computer chooses lizard
Computer wins!

Player chooses lizard
Computer chooses scissors
Computer wins!

Player chooses scissors
Computer chooses Spock
Computer wins!

Note that, for this initial mini-project, we will focus only on testing whether your implementation of rpsls() works correctly on valid input. For more helpful tips on implementing this mini-project, please visit the Code Clinic Tips page for this mini-project.

# python 2.7

import random

names = ["rock", "Spock", "paper", "lizard", "scissors"]

# 辅助函数：名字转数字
def name_to_number(name):
    global names
    return names.index(name)
    
# 辅助函数：数字转名字
def number_to_name(number):
    global names
    return names[number]

# 石头、布、剪刀、蜥蜴、斯波克
# Rock-paper-scissors-lizard-Spock
# 石头 < 斯波克 < 布 < 蜥蜴 < 剪刀
def rpsls(player_choice):
    print 
    
    player_number = name_to_number(player_choice)
    print 'Player chooses %s.' % player_choice
    
    comp_number = random.randrange(5)
    comp_choice = number_to_name(comp_number)
    print 'Computer chooses %s.' % comp_choice
    
    res = (player_number - comp_number) % 5
    if res in [1,2]:
        print 'Player wins!'
    elif res in [3,4]:
        print 'Computer wins!'
    elif res == 0:
        print 'None wins!'
    
# test!
print name_to_number("rock")
print name_to_number("paper")
print name_to_number("scissors")
print name_to_number("lizard")
print name_to_number("Spock")

print number_to_name(0)
print number_to_name(1)
print number_to_name(2)
print number_to_name(3)
print number_to_name(4)

rpsls("rock")
rpsls("paper")
rpsls("scissors")
rpsls("lizard")
rpsls("Spock")