Python 中的 Else 语句无法正常工作

Question

Was wondering if anyone could help me fix the last else statement with the error message. It works if I type in anything else that's not YyNn, however, the error message still does show up if I type in YyNn. I've been at it all night, and I feel like I'm missing the obvious answer - but it's been driving me crazy. Would appreciate an solution for this. Thanks very much.

import random
score = 0

def rollAllDice():
   values=random.randint(1,6), random.randint(1,6), random.randint(1,6), random.randint(1,6), random.randint(1,6)
   print("You rolled 5 dice. The values are:")
   print("Die 1:", values[0]) 
   print("Die 2:", values[1]) 
   print("Die 3:", values[2]) 
   print("Die 4:", values[3]) 
   print("Die 5:", values[4])
   return values
myDice=rollAllDice()

def allSame(myDice):
    result = myDice[0] == myDice[1] and myDice[0] == myDice[2] and myDice[0] == myDice[3] and myDice[0] == myDice[4]
    len(set(myDice)) == 1
    return result

def diceReroll(myDice):
   if allSame(myDice):
      if keepDie1[0] in 'YyNn':
         die1 = random.randint(1,6)
      elif keepDie2[1] in 'YyNn':
         die2 = random.randint(1,6)
      elif keepDie3[2] in 'YyNn':
         die3 = random.randint(1,6)
      elif keepDie4[3] in 'YyNn':
         die4 = random.randint(1,6)
      elif keepDie5[4] in 'YyNn':
         die5 = random.randint(1,6)
   else: # < ---- the else statement I need help on.
      print("I'm sorry. Please only enter Y or N.")

keepDie1=input("\nWould you like to reroll die 1? [Y/N]: ")
keepDie2=input("Would you like to reroll die 2? [Y/N]: ")
keepDie3=input("Would you like to reroll die 3? [Y/N]: ")
keepDie4=input("Would you like to reroll die 4? [Y/N]: ")
keepDie5=input("Would you like to reroll die 5? [Y/N]: ")
diceReroll(myDice)

Answer 1

I took the liberty to make a few assumptions about your code. If you think I went too far, let me know in the comments and I will refractor the answer according to your needs.

The base issue with the if/else loop is indentation (as already mentioned by others in the comments). But I think the real reason why you have this issue lies with the structure of your code. Thus I would suggest you make two changes that would isolate the user input and remove the problematic if/else clause.

First, you are validating the input in your dice rolling logic, hence having your if/else loop:

if allSame(myDice):
      if keepDie1[0] in 'YyNn':
         die1 = random.randint(1,6)
      elif keepDie2[1] in 'YyNn':
         die2 = random.randint(1,6)
      elif keepDie3[2] in 'YyNn':
         die3 = random.randint(1,6)
      elif keepDie4[3] in 'YyNn':
         die4 = random.randint(1,6)
      elif keepDie5[4] in 'YyNn':
         die5 = random.randint(1,6)
   else: # < ---- the else statement I need help on.
      print("I'm sorry. Please only enter Y or N.")

The else part here, as @Selcuk has noted is badly indented, resulting in you getting that error message. This function already contains your application logic and it should not be dealing with user input validation at all.

I would suggest you rewrite the user input part as a separate function (the change to the user prompt message is called an f-string. You can look it up in case you don't understand it):

def diceRerollPrompt(diceNumber):
    while True:
        prompt = input(f'Would you like to reroll die {diceNumber}? [Y/N]: ').upper()
        if prompt in 'YN':
            return prompt
        else:
            print("I'm sorry. Please only enter Y or N.")

keepDie1=diceRerollPrompt(1)
keepDie2=diceRerollPrompt(2)
keepDie3=diceRerollPrompt(3)
keepDie4=diceRerollPrompt(4)
keepDie5=diceRerollPrompt(5)

This piece of code would repeatedly ask the user to input characters until our user enters yYn or N. It ensures that if the user makes a mistake, the user is immediately telegraphed that his/her input is wrong. You also isolate your code from bad input very early on and not need to write heavy validation in the business logic greatly simplifying your allSame() function. Win-win for you and the user.

Afterwards, you can simply delete the problematic if/else loop at all and change your diceReroll function like this:

def diceReroll(myDice):
   if allSame(myDice):
      if keepDie is 'Y':
         die1 = random.randint(1,6)
      elif keepDie2 is 'Y':
         die2 = random.randint(1,6)
      elif keepDie3 is 'Y':
         die3 = random.randint(1,6)
      elif keepDie4 is 'Y':
         die4 = random.randint(1,6)
      elif keepDie5 is 'Y':
         die5 = random.randint(1,6)

Note that I took the liberty to change the YyNn to just Y as you would not want to reroll the dice if the user said NO, right?

Full solution below

import random
score = 0

def rollAllDice():
   values=random.randint(1,6), random.randint(1,6), random.randint(1,6), random.randint(1,6), random.randint(1,6)
   print("You rolled 5 dice. The values are:")
   print("Die 1:", values[0]) 
   print("Die 2:", values[1]) 
   print("Die 3:", values[2]) 
   print("Die 4:", values[3]) 
   print("Die 5:", values[4])
   return values
myDice=rollAllDice()

def allSame(myDice):
    result = myDice[0] == myDice[1] and myDice[0] == myDice[2] and myDice[0] == myDice[3] and myDice[0] == myDice[4]
    len(set(myDice)) == 1
    return result

def diceReroll(myDice):
   if allSame(myDice):
      if keepDie1 is 'Y':
         die1 = random.randint(1,6)
      elif keepDie2 is 'Y':
         die2 = random.randint(1,6)
      elif keepDie3 is 'Y':
         die3 = random.randint(1,6)
      elif keepDie4 is 'Y':
         die4 = random.randint(1,6)
      elif keepDie5 is 'Y':
         die5 = random.randint(1,6)

def diceRerollPrompt(diceNumber):
    while True:
        # if you want to use the simple string concatenation:
        # prompt = input('Would you like to reroll die ' + diceNumber +'? [Y/N]: ').upper()
        prompt = input(f'Would you like to reroll die {diceNumber}? [Y/N]: ').upper()
        if prompt in 'YN':
            return prompt
        else:
            print("I'm sorry. Please only enter Y or N.")

keepDie1=diceRerollPrompt(1)
keepDie2=diceRerollPrompt(2)
keepDie3=diceRerollPrompt(3)
keepDie4=diceRerollPrompt(4)
keepDie5=diceRerollPrompt(5)
diceReroll(myDice)

'''

Answer 2

Excellent response by @Simas.

I would just like point out that you will never be able to re-roll anything unless all 5 dice are the same. The reason is that in allSame you are using the logical and operator. By definition, all conditions must be true in order for it to return true. Therefore, if you get even 1 false, it returns false. So in diceReroll , the first if condition is always going to evaluate to false . And maybe this is what you want, however you shouldn't be asking if the user wants to re-roll anything if that's the case. By changing the and s to or s you then get the behavior that the dice re-roll will only work if the first dice is equal to at least one other die. (Not sure what the len(set(mydice)) == 1 is for...it seems to be a boolean statement but isn't connected to the previous statement by an and or or )

And with the current if-elif structure, only the first dice to have a 'Y' will be re-rolled because after it evaluates it, it ignores the rest. So, this may be better suited as a series of if statements. Also, all the keepDie x needs to have 0 in the brackets, otherwise you get an index out of bounds.

def diceReroll(myDice):
    if allSame(myDice):
        if keepDie1[0] is 'Y':
            die1 = random.randint(1, 6)
            print(die1)
        if keepDie2[0] is 'Y':
            die2 = random.randint(1, 6)
            print(die2)
       if keepDie3[0]is 'Y':
            die3 = random.randint(1, 6)
            print(die3)
       if keepDie4[0] is 'Y':
            die4 = random.randint(1, 6)
            print(die4)
       if keepDie5[0] is 'Y':
            die5 = random.randint(1, 6)
            print(die5)