Python：IndexError：列表索引超出范围

Posted 2023-02-23

【中文标题】Python：IndexError：列表索引超出范围

【英文标题】：Python: IndexError: list index out of range

【发布时间】：2012-03-04 14:07:54

【问题描述】：

我想我的程序已经完成了，但是……它不起作用。我正在尝试编写一个模拟彩票游戏的程序，但是当我尝试检查用户的猜测与彩票上的猜测次数时，我收到一个错误，告诉我“列表索引超出范围”。我认为这与我将随机数字分配给“a”、“b”、“c”等的代码部分有关。但我不确定。

这是完整的代码：

import random

def main():
random.seed()

#Prompts the user to enter the number of tickets they wish to play.
tickets = int(input("How many lottery tickets do you want?\n"))

#Creates the dictionaries "winning_numbers" and "guess." Also creates the variable "winnings" for total amount of money won.
winning_numbers = []
guess = []
winnings = 0

#Generates the winning lotto numbers.
for i in range(tickets):
    del winning_numbers[:]

    a = random.randint(1,30)
    while not (a in winning_numbers):
        winning_numbers.append(a)

    b = random.randint(1,30)
    while not (b in winning_numbers):
        winning_numbers.append(b)

    c = random.randint(1,30)
    while not (c in winning_numbers):
        winning_numbers.append(c)

    d = random.randint(1,30)
    while not (d in winning_numbers):
        winning_numbers.append(d)

    e = random.randint(1,30)
    while not (e in winning_numbers):
        winning_numbers.append(e)

    print(winning_numbers)
    getguess(guess, tickets)
    nummatches = checkmatch(winning_numbers, guess)

    print("Ticket #"+str(i+1)+": The winning combination was",winning_numbers,".You matched",nummatches,"number(s).\n")

    if nummatches == 0 or nummatches == 1:
        winnings = winnings + 0
    elif nummatches == 2:
        winnings = winnings + 10
    elif nummatches == 3:
        winnings = winnings + 500
    elif nummatches == 4:
        winnings = winnings + 20000
    elif nummatches == 5:
        winnings = winnings + 1000000

print("You won a total of",winnings,"with",tickets,"tickets.\n")

#Gets the guess from the user.
def getguess(guess, tickets):
del guess[:]

for i in range(tickets):
    bubble = input("What numbers do you want to choose for ticket #"+str(i+1)+"?\n").split(" ")
    guess.append(bubble)
print(bubble)

#Checks the user's guesses with the winning numbers.
def checkmatch(winning_numbers, guess):
match = 0
for i in range(5):

    if guess[i] == winning_numbers[i]:
        match = match+1

return match

main()

这是我得到的错误：

Traceback (most recent call last):
  File "C:\Users\Ryan\Downloads\Program # 2\Program # 2\lottery.py", line 85, in <module>
    main()
  File "C:\Users\Ryan\Downloads\Program # 2\Program # 2\lottery.py", line 45, in main
   nummatches = checkmatch(winning_numbers, guess)
File "C:\Users\Ryan\Downloads\Program # 2\Program # 2\lottery.py", line 79, in checkmatch
    if guess[i] == winning_numbers[i]:
IndexError: list index out of range

【问题讨论】：

阅读回溯，在大多数情况下会有所帮助。

wining_numbers 多长时间？我想你会发现它a=randint(1,30) inside while 循环。否则，它只会运行一次。

另外，绝对没有理由在函数getguess中使用del myList[:]这一行，guess是在函数范围内定义的。用guess = []初始化猜测。

IndexError: list assignment index out of range 的可能重复项

【参考方案1】：

正如错误说明，问题出在以下行：

if guess[i] == winning_numbers[i]

错误是您的列表索引超出范围 - 也就是说，您试图引用一些甚至不存在的索引。如果不完全调试您的代码，我会检查您根据输入添加猜测的行：

for i in range(tickets):
    bubble = input("What numbers do you want to choose for ticket #"+str(i+1)+"?\n").split(" ")
    guess.append(bubble)
print(bubble)

你给用户的猜测数量是基于

# Prompts the user to enter the number of tickets they wish to play.
tickets = int(input("How many lottery tickets do you want?\n"))

所以如果他们想要的票数少于5，那么你的代码在这里

for i in range(5):

if guess[i] == winning_numbers[i]:
    match = match+1

return match

会抛出错误，因为guess 列表中的元素并不多。

【讨论】：

实际上，他的错误是在更早的时候引起的。根据他的输入语句，bubble 是一个字符串列表。然后，此列表将附加到 guess。所以guess 看起来像：[['12', '30', '12', '23'. '3'], ['4','5','7','8','16']]。正确的列表方法是guess.extend()。此外，这些值是字符串，因此即使它们进行比较，比较也将永远返回 true。

【参考方案2】：

这是您的代码。我假设您正在使用 python 3，基于您对 print() 和 input() 的使用：

import random

def main():
    #random.seed() --> don't need random.seed()

    #Prompts the user to enter the number of tickets they wish to play.

    #python 3 version:
    tickets = int(input("How many lottery tickets do you want?\n"))

    #Creates the dictionaries "winning_numbers" and "guess." Also creates the variable "winnings" for total amount of money won.
    winning_numbers = []
    winnings = 0

    #Generates the winning lotto numbers.
    for i in range(tickets * 5):
        #del winning_numbers[:] what is this line for?
        randNum = random.randint(1,30)
        while randNum in winning_numbers:    
            randNum = random.randint(1,30)
        winning_numbers.append(randNum)

    print(winning_numbers)
    guess = getguess(tickets)
    nummatches = checkmatch(winning_numbers, guess)

    print("Ticket #"+str(i+1)+": The winning combination was",winning_numbers,".You matched",nummatches,"number(s).\n")

    winningRanks = [0, 0, 10, 500, 20000, 1000000]

    winnings = sum(winningRanks[:nummatches + 1])

    print("You won a total of",winnings,"with",tickets,"tickets.\n")


#Gets the guess from the user.
def getguess(tickets):
    guess = []
    for i in range(tickets):
        bubble = [int(i) for i in input("What numbers do you want to choose for ticket #"+str(i+1)+"?\n").split()]
        guess.extend(bubble)
        print(bubble)
    return guess

#Checks the user's guesses with the winning numbers.
def checkmatch(winning_numbers, guess):
    match = 0
    for i in range(5):
        if guess[i] == winning_numbers[i]:
            match += 1
    return match

main()

【参考方案3】：

我认为您的意思是将随机 a、b、c 等的滚动放在循环中：

a = None # initialise
while not (a in winning_numbers):
    # keep rolling an a until you get one not in winning_numbers
    a = random.randint(1,30)
    winning_numbers.append(a)

否则，a 将只生成一次，如果它已经在winning_numbers 中，则不会添加。由于a 的生成在while 之外（在您的代码中），如果a 已经在winning_numbers 中，那么太糟糕了，它不会被重新滚动，并且您将少一个中奖号码。

这可能是导致您在if guess[i] == winning_numbers[i] 中出错的原因。 （您的 winning_numbers 的长度并不总是 5）。

【讨论】：

只有在 a 不在winning_numbers 中时才会运行此代码。换句话说，如果有重复，则不会附加任何数字。请记住，while 会在运行前检查运行条件。