While 循环：列表索引超出范围

Question

I've been making a function to search through two lists and check if a character is in both lists.The error

"IndexError: list index out of range"

keeps coming up. I put this through python Tutor and it seems like the while loop is totally ignored.I'm coding this search without using the in function in an if statement . Any help would be much appreciated!

Here is my code:

aList = ["B" , "S" , "N" , "O" , "E" , "U" , "T" ]
userInput = "TOE"
userInputList = list(userInput)
letterExists = 0

while (letterExists < len(userInput)):
    for i in aList:
        if (i == userInputList[letterExists]):
            letterExists +=1

if (letterExists == len(userInput)):
        print("This word can be made using your tiles")

Answer 1

letterExists < len(userInput) only guarantees that there is 1 more letter that can be processed, but you may iterate more than 1 time by means of the for loop.

By the way, you can write this condition very nicely using set :

the_set = set(["B", "S", ...])
if(all(x in the_set for x in userInput)):
   ...

Answer 2

你可以使用 python magic 并像这样写：

len([chr for chr in userInput if chr in aList]) == len(userInput)

Answer 3

Looking at your code and without trying to do better, I found that a break is missing after the incrementation of letterExists . Here is the fixed code:

aList = ["B" , "S" , "N" , "O" , "E" , "U" , "T" ]
userInput = "TOE"
userInputList = list(userInput)
letterExists = 0

while (letterExists < len(userInput)):
    for i in aList:
        if (i == userInputList[letterExists]):
            letterExists +=1
            break

if (letterExists == len(userInput)):
        print("This word can be made using your tiles")

However, a better pythonic solution is the following (same as xtofl 's answer):

aList = ["B" , "S" , "N" , "O" , "E" , "U" , "T" ]
userInput = "TOF"

a = all([letter in aList for letter in userInput])

if (a):
    print("This word can be made using your tiles")