import random

#generateList
#This function takes no input and randomly generates a list of four characters
#selected from the list R, G, B, Y.  It then returns the list.
#input: none
#output: a list of four characters
def generateList():
    #create list of 4 possible letters
    choices = ['R', 'G', 'B', 'Y']
    
    #create empty solution
    solution = []

    #four times
    #  generate random int to represent position in list of choices
    #  add elt at randomly chosen position in choices to solution
    for i in range(4):
        randnum = random.randint(0, 3)
        solution.append(choices[randnum])

    #return new list of characters
    return solution

#testing generateList()
#result = generateList()
#print result

#getGuess
#This function takes no input and prompts the user for four characters.
#The characters are stored in a list that is then returned.
#input: none
#output: a list of four characters
def getGuess():
    #create an empty list
    fullguess = []
    
    #four times
    #  prompt user for guess
    for i in range(4):
        guess = raw_input("Enter the next character of your guess [R, G, B, Y]: ")
        #validate input
        while guess != 'R' and guess != 'G' and guess != 'B' and guess != 'Y':
            guess = raw_input("Bad input.  Enter another guess - RGB or Y: ") 
        fullguess.append(guess)
        
    return fullguess 

#testing
#userguess = getGuess()
#print userguess

#compare
#This function takes as input two lists and returns True if the lists
#contain the same four characters in the same locations and False otherwise.
#input: two lists
#output: boolean
def compare(solution, guess):

    #loop - four times
    #  compare solution at pos i to guess at pos i
    for i in range(4):
        if solution[i] != guess[i]:
            return False
    return True

#testing
#list1 = ['R', 'B', 'B', 'Y']
#list2 = ['R', 'B', 'B', 'G']
#result = compare(list1, list2)
#print result

#main logic
#generate a list of 4 random characters
solution = generateList()
userinput = 'y'
#while the user wants to guess again
while userinput == 'y':
    #  get a guess from the user
    guess = getGuess()
    #  compare the guess to the random list
    result = compare(solution, guess)
    #  if the user guessed correctly
    if compare == True:
        #    print a message
        print "You guessed correctly!"
        #    set guess again to be False
        userinput = 'n'
    else:
        print "Incorrect guess."
        userinput = raw_input("Would you like to guess again? ")
        #  else
        #    ask if the user wants to guess again