python代码不起作用

Question

i have the following code for a rock paper scissors game:

import random
def rps():  
   computerchoice = random.randint(1,3) 
   if computerchoice == 1: 
     computerchoice = "rock" 
   elif computerchoice == 2: 
     computerchoice = "paper" 
   elif computerchoice == 3: 
     computerchoice = "scissors"
   choice = raw_input("Rock, paper, or scissors?:") 
   choice = choice.lower() 
   if choice != "rock":
     if choice != "paper":
       if choice != "scissors":
         print "Check your spelling and try again." 
         rps()
       else:
         pass
     else:
       pass 
   else: 
     print "The computer chose " + computerchoice + "." 
     if choice == computerchoice: 
       print "It's a draw!" 
     elif choice + computerchoice == "rockpaper": 
       print "Computer wins, paper covers rock!" 
     elif choice + computerchoice == "rockscissors": 
       print "Player wins, rock crushes scissors!" 
     elif choice + computerchoice == "paperrock": 
       print "Player wins, paper covers rock!" 
     elif choice + computerchoice == "paperscissors": 
       print "Computer wins, scissors cut paper!" 
     elif choice + computerchoice == "scissorsrock":
       print "Computer wins, rock crushes scissors!"
     elif choice + computerchoice == "scissorspaper":
       print "Player wins, scissors cuts paper!" 
rps()

Whenever i run it, it works fine if i pick rock, but if i pick paper or scissors, the code stops. It wont throw any kind of error, it just stops. Please help me!

Answer 1

This should be closer to what you need:

import random
def rps():
    computerchoice = random.randint(1,3)
    if computerchoice == 1:
        computerchoice = "rock"
    elif computerchoice == 2:
        computerchoice = "paper"
    elif computerchoice == 3:
        computerchoice = "scissors"
    choice = raw_input("Rock, paper, or scissors?:")
    choice = choice.lower()
    if choice not in ["scissors","paper","rock"]: # check if choice is valid
        rps()
    print "The computer chose " + computerchoice + "."
    if choice == computerchoice:   # move on to your comparison checks 
        choice + computerchoice
        print "It's a draw!"
    elif choice + computerchoice == "rockpaper":
        print "Computer wins, paper covers rock!"
    elif choice + computerchoice == "rockscissors":
        print "Player wins, rock crushes scissors!"
    elif choice + computerchoice == "paperrock":
        print "Player wins, paper covers rock!"
    elif choice + computerchoice == "paperscissors":
        print "Computer wins, scissors cut paper!"
    elif choice + computerchoice == "scissorsrock":
        print "Computer wins, rock crushes scissors!"
    elif choice + computerchoice == "scissorspaper":
        print "Player wins, scissors cuts paper!"
rps()

Answer 2

The problem is from the first choice if statement:

    if choice != "rock":
        if choice != "paper":
            if choice != "scissors":

when rock is selected it jumps to the else statement without evaluating the other two if statements. A more intuitive but admittedly non-Pythonic way is to have a series of nested if statements:

import random
def rps():  
    computerchoice = random.randint(1,3) 
    if computerchoice == 1: 
        computerchoice = "rock" 
    elif computerchoice == 2: 
        computerchoice = "paper" 
    elif computerchoice == 3: 
        computerchoice = "scissors"
    choice = raw_input("Rock, paper, or scissors?:") 
    choice = choice.lower() 
    print "The computer chose " + computerchoice + "." 
    if choice == 'rock':
        if computerchoice == 'rock':
            print 'Draw: you both picked rock'
        elif computerchoice == 'scissors':
            print 'You win! Rock beats scissors'
        elif computerchoice == 'paper':
            print 'You lose.  Try again'
    elif choice == 'paper':
        if computerchoice == 'rock':
            print 'You win!'
        elif computerchoice == 'scissors':
            print 'You lose.'
        elif computerchoice == 'paper':
            print 'You draw.'
    elif choice == 'scissors':
        if computerchoice == 'rock':
            print 'You lose.'
        elif computerchoice == 'scissors':
            print 'You draw.'
        elif computerchoice == 'paper':
            print 'You win.'
    else:
        print 'I am sorry, I could not make out what you typed.  Try again'
        rps()

rps()

Answer 3

Loop just your input. Don't recursively call the whole game again. Also setup a variable to test against for valid choices. Also if you break out the win conditions you can add to it easily. Maybe something like this

import random
CHOICES = {'rock': 'crushes', 'paper': 'covers', 'scissors': 'cuts'}


def win(p1, p2):
    if p1 == p2:
        return 0
    if p1 == 'rock':
        return 2 if p2 == 'paper' else 1
    if p1 == 'paper':
        return 2 if p2 == 'scissors' else 1
    if p1 == 'scissors':
        return 2 if p2 == 'rock' else 1


def rps():
   computerchoice = random.choice(CHOICES.keys())
   choice = raw_input("Rock, paper, or scissors?:").lower()
   while choice not in CHOICES:
       print "Check your spelling and try again."
       choice = raw_input("Rock, paper, or scissors?:").lower()
   print "The computer chose %s." % computerchoice
   winner = win(choice, computerchoice)
   if winner==0:
       print "It's a draw!"
   if winner==1:
       print "Player wins, %s %s %s!" % (choice, CHOICES[choice], computerchoice)
   if winner==2:
       print "Computer wins, %s %s %s!" % (computerchoice, CHOICES[computerchoice], choice)


rps()

Now say you want to add lizard and spock . Just update CHOICES and the win() function. :)

Answer 4

Check theese lines out:

 if choice != "paper": if choice != "scissors": print "Check your spelling and try again." rps() else: pass #here you tell it to do nothing when you choose "scissors" else: pass #here you tell it to do nothing when you choose "paper"

I think you just need to re-sort your if/else statements :-)

Answer 5

The else section (containing the brains of your code) of the first if :

if choice != "rock":
    if choice != "paper":
        if choice != "scissors":

never runs if player doesn't select 'rock' ie 'paper' , 'scissors' and any invalid input will ensure the else containing the important section of your code doesn't get executed.

Answer 6

you definitely don't need recursion for such a simple algorithm (calling rps() from rps() )

you should try to implement it like this:

input == ""
while input != "quit":
  input = raw_input(...)
  if input not in ["r", "p", "s"]: continue
  computer_choice = ...
  if foo beats bar: print ...
  if bar beats foo: print ...

Answer 7

Let's look at this.

if choice != "rock":
  if choice != "paper":
    if choice != "scissors":
      print "Check your spelling and try again." 
      rps()
    else:
      pass
  else:
    pass 
else: 
  # Do stuff...

You input scissors.

• Does "scissors" != "rock"? Yes, so lets go further.

• Does "scissors" != "paper"? Yes, so lets go further.

• Does "scissors" != "scissors"? No, so let's look at the alternative else clause:

   else: pass

This code does nothing... Every other if/else clause is then broken out of after this... See the issue?

There are also a lot of simplifications you can do, for example you can make use of tables and lists more often instead of using so many if statements . For example (although the code remains largely untested):

import random

def convert_choice(choice):
    choice_map = {"rock":0, "paper":1, "scissors":2}
    return choice_map[choice]

def rock_paper_scissors():
    choices = ["rock", "paper", "scissors"]
    computer_choice = random.randint(0,2)
    player_choice = raw_input("Rock, paper, or scissors? ") 
    raw_player_choice = convert_choice(player_choice) * 3
    print "Copmuter played: " + choices[computer_choice]
    print "You played: " + player_choice
    win_states = {0:"tied", 3:"won", 6:"loss", 
                  -1:"loss", 2:"tied", 5:"won",
                  -2:"won", 1:"loss", 4:"tied"}
    print "You " + win_states[raw_player_choice - computer_choice]

def main():
    rock_paper_scissors()

if __name__ == "__main__":
    main()