基于Python文本的游戏：使用While-Loop和Try-Except进行猜测游戏

Question

I'm writing a simple text-based game to enhance my knowledge of Python. In one stage of the game, the user needs to guess a number in the set [1, 5] in order to have his or her wish granted. They only get three attempts. I have two questions:

1) Lets assume that genie_number is randomly selected to be 3. Does this value change after each guess by the user? I don't want the program to randomly choose another integer after each guess. It should remain the same so the user has a 3/5 chance of guessing it correctly.

2) I want to penalize users for not guessing only an integer, and I've done that under the except ValueError section. But if the user makes three non-integer guesses in a row and exhausts all their attempts, I want the loop to re-direct to else: dead("The genie turns you into a frog.") . Right now it gives me the error message below. How do I fix this?

'Before I grant your first wish,' says the genie, 'you must answer this
'I am thinking of a discrete integer contained in the set [1, 5]. You ha
(That isn't much of a riddle, but you'd better do what he says.)
What is your guess? > what
That is not an option. Tries remaining: 2
What is your guess? > what
That is not an option. Tries remaining: 1
What is your guess? > what
That is not an option. Tries remaining: 0
Traceback (most recent call last):
  File "ex36.py", line 76, in <module>
    start()
  File "ex36.py", line 68, in start
    lamp()
  File "ex36.py", line 48, in lamp
    rub()
  File "ex36.py", line 38, in rub
    wish_1_riddle()
  File "ex36.py", line 30, in wish_1_riddle
    if guess == genie_number:
UnboundLocalError: local variable 'guess' referenced before assignment

Here is my code so far:

def wish_1_riddle():
    print "\n'Before I grant your first wish,' says the genie, 'you must answer this riddle!'"
    print "'I am thinking of a discrete integer contained in the set [1, 5]. You have three tries.'"
    print "(That isn't much of a riddle, but you'd better do what he says.)"

    genie_number = randint(1, 5)
    tries = 0
    tries_remaining = 3

    while tries < 3:
        try:
            guess = int(raw_input("What is your guess? > "))
            tries += 1
            tries_remaining -= 1

            if guess == genie_number:
                print "Correct!"
                wish_1_grant()
            else:
                print "Incorrect! Tries remaining: %d" % tries_remaining
                continue
        except ValueError:
            tries += 1
            tries_remaining -= 1
            print "That is not an option. The genie penalizes you a try. Be careful!"
            print "Tries remaining: %d" % tries_remaining

    if guess == genie_number:
        wish_1_grant()
    else:
        dead("The genie turns you into a frog.")

Answer 1

Answering your first question, no. If you keep calling randint(1, 5) , yes it will change, but once you assign it, the value is fixed:

>>> import random
>>> x = random.randint(1, 10)
>>> x
8
>>> x
8
>>> x
8
>>> random.randint(1, 10)
4
>>> random.randint(1, 10)
8
>>> random.randint(1, 10)
10

As you can see, once we assign the random number to x , x always stays the same. However, if we keep calling the randint() , it changes.

Answering your second question, you should not add 1 to tries right after the int(raw_input()) , if the value is an integer, it will also addd 1 to tries. Instead, try to incorporate your code into something like below:

>>> tries = 0
>>> while tries < 3:
...     try:
...             x = raw_input('Hello: ')
...             x = int(x)
...     except ValueError:
...             tries+=1
... 
Hello: hello
Hello: 1
Hello: 4
Hello: bye
Hello: cool
>>> 

You are getting the error, because you have incorrectly answered all 3 of the times. Therefore, nothing is assigned to guess . After your while loop, you try to see if guess is something, which it isn't:

>>> tries = 0
>>> while tries < 3:
...     try:
...             guess = int(raw_input('Enter input: '))
...             print guess
...     except ValueError:
...             tries+=1
... 
Enter input: hello
Enter input: bye
Enter input: good morning
>>> guess
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'guess' is not defined

However, if you give correct input, guess becomes something:

>>> tries = 0
>>> while tries < 3:
...     try:
...             guess = int(raw_input('Enter input: '))
...             print guess
...     except ValueError:
...             tries+=1
... 
Enter input: 4
4
Enter input: hello
Enter input: 9
9
Enter input: bye
Enter input: 6
6
Enter input: greetings
>>> guess
6
>>> 

EDIT

Contrary to what @LosFrijoles about the problem being with the scope, the error was actually due to the lack of correct input:

>>> x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined
>>> for k in range(1):
...     x = 1
...     print x
... 
1
>>> x
1
>>> 

As you can see, the variable x exists in both the for loop and in the regular shell, so it is not a scope issue:

>>> x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined
>>> for k in range(1, 3):
...     try:
...             x = int(raw_input('Hello: '))
...             print x 
...     except ValueError:
...             pass
... 
Hello: hello
Hello: bye
>>> x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined
>>> 

As you can see, it is a error error... :) Because of the error, x never gets assigned unless we actually give an integer input, because the code never reaches the print x , because it breaks due to the error:

>>> x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined
>>> for k in range(1, 3):
...     try:
...             x = int(raw_input('Hello: '))
...             print x
...     except ValueError:
...             pass
... 
Hello: hello
Hello: 8
8
>>> x
8
>>> 

When we do give an integer input, x becomes valid.