Python 列表索引必须是整数或切片而不是字符串

Question

image of code if not understandable

The image shows the code I have written, I want to swap item positions but I am getting list indices must be integer or slice not string. I have tried many different ways but still dont seem to get the hang of it.

choice = ""
lists = []
while True:

choice = input("Try out inv commands: ")
if choice == 'inv':
    print('Backpack has ' + str(len(lists)) + ' iteams: ' + str(lists))
elif 'inv pick' in choice:
    iteams1 = choice.split('inv pick ')
    iteams2 = iteams1[1].split(' ')
    try:
        if iteams2[1] != '':
            add = lists.insert(int(iteams2[1]), iteams2[0])
            print(str(iteams2), ' has been added')
    except IndexError:
        lists.extend(iteams2)
elif 'inv drop' in choice:
    iteams1 = choice.split('inv drop ')
    iteams2 = iteams1[-1].split(' ')
    if iteams2[-1] != '':
        removed = lists.remove(iteams2[0])
        print(str(iteams2), ' has been dropped')
elif 'inv swap' in choice:
    iteams1 = choice.split('inv swap')
    iteams2 = iteams1[1].split(' ')
    try:
        if iteams2[1] != '':
            pos1, pos2 = iteams2[2], iteams2[1]
            lists[pos1], lists[pos2] = lists[pos2], lists[pos1]
            print('swapped ')
    except IndexError:
        enter code herelists.extend(iteams2)

Answer 1

Instead how about reversing the list?

lists.reverse()

If you use reversed(lists) , then it will print the list reversed.

Answer 2

Well, you see, on line 30 you assigned

pos1, pos2 = iteams[2], iteams[1]

That means that pos1 and pos2 are string variables. On line 31, you tried to use lists[pos2] , but that means lists["something"] instead of lists[0] . Always bear in mind what you value and data type assign to each variable.

Answer 3

As others have suggested, please follow the guideline to ask questions in stackoverflow to acommodate others in answering :)

To answer the question, the error says that it is caused by using a string on list indexes. Indeed, your variables are strings and you tried to use it in list indexes. eg x[0] to get element of a list on 0th position, but not x['0']

Instead, you can try using

  pos1, pos2 = int(iteams[2]), int(iteams[1]) 

but I'd suggest rewriting the code to avoid casting types and future confusions

Answer 4

As I see, you are giving strings as indices like the error mentions.

When you split the choice variable, it returns list of strings. You need to convert those strings to integers or slices if you would like to access elements in those indices.

pos1, pos2 = int(iteams2[2]),int(iteams2[-1])

This works in your case I guess.

Don't forget to paste your code to your question next time, screenshot would be hard to read for people :)