On 10/31/2011 11:41 AM, Joel Montes de Oca wrote:
Hello everyone,
I am having a little trouble with a block of code that isn't behaving
the way I would expect. Maybe you can give me a hand and point where
it is going wrong.
The function that is not working correctly belongs to a Paper Rock
Scissor game I am making.
This particular function is responsible to:
a) Get the user's choice (Paper, Rock, or Scissors)
b) Return the user's choice within the variable choice to the
function that called it.
The function works correctly as long as the user _does not try to
enter a string other than_ 'P', 'R', or 'S'.
Logic:
Take the user's string and put it in the variable choice.
If choice is not 'P', 'R', or 'S'then pass a message to the user
and call the function again.
If the choice is 'P', 'R', or 'S'then return choice to where it
was called from.
The problem is this.
When the user enters a string other than the valid ones, the if
statements catches it and calls the same function again so the user
can enter a valid string. But the variable choice does not get
assigned the new string entered by the user, instead it is empty.
I would expect if the function runs again, the variable choice would
be updated to the last value given by the user.
The function: ( http://dpaste.com/644857/)
def UserChoice (): # The function that returns the choice from the user
print 'Please select (P) for paper, (R) for Rock, or (S) for Scissors.'
choice = raw_input('What is your selection?:')
if choice.lower() not in ('p', 'r','s'): # Converts the user's
choice to lowercase and confirms the choice is valid
print 'I am sorry, you entered\'' + choice.upper() + '\'
which is an invalid response. Please try again.'
raw_input('Press Enter to try again.')
UserChoice () # If the choice is not valid, run the
function over
else:
return choice
Output with no problems: ( http://dpaste.com/644866/)
<http://dpaste.com/644866/>
Welcome to the PRS game.
Please select (P) for paper, (R) for Rock, or (S) for Scissors.
What is your selection?: s
You threw down Scissors while the computer threw down Rock
LOOSE
Output with problems: ( http://dpaste.com/644868/)
Welcome to the PRS game.
Please select (P) for paper, (R) for Rock, or (S) for Scissors.
What is your selection?: L
I am sorry, you entered 'L' which is an invalid response. Please try again.
Press Enter to try again.
Please select (P) for paper, (R) for Rock, or (S) for Scissors.
What is your selection?: s
You threw down None while the computer threw down Paper
LOOSE
Here's the full source code in case the problem is outside of the
function: ( http://dpaste.com/644873/)
import random # Import the random library
def main (): # The main function that gets called from main()
print '\nWelcome to the PRS game.\n'
choice = UserChoice () # Gets the choice from the user
cchoice = ComputerChoice () # Gets the choice from the
computer
PrintOutcome (choice, cchoice) # Passes both choices to the
PrintChoice function for display
return 0
def UserChoice (): # The function that returns the choice from the user
print 'Please select (P) for paper, (R) for Rock, or (S) for Scissors.'
choice = raw_input('What is your selection?:')
if choice.lower() not in ('p', 'r','s'): # Converts the user's
choice to lowercase and confirms the choice is valid
print 'I am sorry, you entered\'' + choice.upper() + '\'
which is an invalid response. Please try again.'
raw_input('Press Enter to try again.')
UserChoice () # If the choice is not valid, run the
function over
else:
return choice
def ComputerChoice (): # The function that returns the choice
from the computer
PRS = ['Rock', 'Paper', 'Scissors'] # A list of choices
cchoice = random.choice(PRS) # Choose a random item from the list
return cchoice # Return the function
def PrintOutcome (UC, CC): # Function responsable to display the
choices and results
PRS = ['Rock', 'Paper', 'Scissors']
# Convert the letters to words
if UC == 'r':
UC = PRS[0]
elif UC == 'p':
UC = PRS[1]
elif UC == 's':
UC = PRS[2]
print '\n\tYou threw down', UC, 'while the computer threw down', CC
+'\n'
# find the outcome of the game
if UC == CC:
print 'We have a tie, both players gain a point!'
elif UC == 'Rock' and CC == 'Scissors':
print 'WIN'
elif UC == 'Paper' and CC == 'Rock':
print 'WIN'
elif UC == 'Scissors' and CC == 'Paper':
print 'WIN'
else:
print 'LOOSE'
return 0
main()
I am using Python 2.7
I am running on Ubuntu 11.10
Thanks for any help
--
-Joel M.
OK everyone,
After burning my little noob brain cells a bit, I came up with this to
solve the problem.
def UserChoice (): # The function that returns the choice from the user
while 1:
print 'Please select (P) for paper, (R) for Rock, or (S) for Scissors.'
choice = raw_input('What is your selection?:')
if choice.lower() in ('p', 'r','s'): # Converts the user's
choice to lowercase and confirms the choice is valid
return choice
break
else:
print 'Try again.'
It puts the choice into a loop and only exits when the user enters a
valid value. It works and it's so much easier to read too!
Thanks for all the help! :)
--
-Joel M.
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