Python 错误：列表索引必须是整数或切片，而不是元组

Question

def openMap(uArr, oArr, i):
    y = int(input("Row Number"))
    x = int(input("Column Number"))
    uArr[y,x] = oArr[y,x]
    printMap(uArr)
    if oArr[y,x] == "X":
        return 0
    else:
        return 1

uArr refers to the user array and oArr to the original array.

I get this error:

list indices must be integers or slices, not a tuple

Can someone help to debug this?

Answer 1

In a normal Python multidimensional list, you can't access elements as uArr[y, x] . Instead use uArr[y][x] .

Answer 2

Perhaps you mean if oArr[y][x] == "X": ? You cannot pass 2 numbers for indexing a list.

By passing [y,x] it means oArr[(y,x)] And list indexing needs an integer. You should do:

if oArr[y][x] == "X":

Answer 3

The error-message indicates a common syntax error in Python.

Syntax-error when indexing

list indices must be integers or slices, not a tuple

It is caused by using the wrong syntax when indexing a list (or array). What your code used as index was x,y was interpreted as tuple like (x,y) .

Correct would be either a single integer, like array[1] or array[x] or a slice like array[1:2] to get second to third element.

See explained in article TypeError: list indices must be integers or slices, not str .

The indexes in any multi-dimensional array or list must be added in separate brackets. So [x][y][z] indexes a single element in a cube or 3D-array, whereas your 2-dimensional array will just use something like [x][y] .

Hot to fix

To fix it, simply replace all [y,x] by [y][x] .

def openMap(uArr, oArr, i):
    y = int(input("Row Number"))
    x = int(input("Column Number"))  # fixed a typo

    uArr[y][x] = oArr[y][x]
    printMap(uArr)
    
    if oArr[y][x] == "X":
        return 0
    else:
        return 1

Bonus-Tip: Validate user-input to avoid out-of-bounds errors

What happens if the user enters -1 or 999999999999 ? Does your array or list allow negative indices or have a size that large?

You should check before and ask for a correct input then.

    last_row = len(oArr)-1  # last index because zero-based
    y = last_row + 1  # initially out-of-bounds to enter the loop
    while not 0 <= y <= last_row:
        y = int(input("Row Number ({}..{}): ".format(0, last_row)))
    
    last_col = len(oArr[0])-1  # suppose it's quadratic = all rows have same length
    x = last_col + 1  # initially out-of-bounds to enter the loop
    while not 0 <= x <= last_col:
        x = int(input("Column Number ({}..{}):".format(0, last_col)))

Note: Technically a negative index like -1 will point to the last element, -2 to the element before last, and so on.

See also related questions:

• Determine Whether Integer Is Between Two Other Integers?
• How to index a list based on user input, and print the result
• IndexError: list index out of range : when a element is poped out of array in python
• Python - Input Validation