Python 'list indices must be integers, not tuple" error

问题

I'm working on moving a robot around a 2d grid room of 8 x 8, and one part is initialising the sensors which consist of the closest 5 tiles around the robot.

self.sensors = [0 for x in xrange(5)]

here I'm creating an empty of array of 5 elements.

but when I attempt to set the value of sensors like this:

    if self.heading == 'East':
        self.sensors[0] = self.room[self.x, self.y-1]
        self.sensors[1] = self.room[self.x+1, self.y-1]
        self.sensors[2] = self.room[self.x+1, self.y]
        self.sensors[3] = self.room[self.x+1, self.y+1]
        self.sensors[4] = self.room[self.x, self.y+1]

I get the error of 'list indices must be integers, not tuples'.

回答1:

You say self.room is a "2d grid" -- I assume it is a list of lists. In this case, you should access its elements as

self.room[self.x][self.y-1]

instead of indexing the outer list with the pair self.x, self.y-1.

回答2:

The problem comes from your self.room.

Beacuse this:

self.room[self.x, self.y-1]

Is the same of:

self.room[(self.x, self.y-1)]

And that's your tuple error.

There are two possibilities:

self.room is a 2D array, which means that you probably meant something like:
```
self.room[self.x][self.y-1]
```
you wanted to slice self.room:
```
self.room[self.x:self.y-1]
```

Please provide more information about self.room.

回答3:

self.room[self.x, self.y-1] indexes self.room with a tuple. If it is a ragged array then you must use self.room[self.x][self.y-1] instead.

回答4:

what is the type of self.room, i think room is a list in this case you have to assign like this

if self.heading == 'East':
   self.sensors[0] = [self.x, self.y-1]

or like this

if self.heading == 'East':
    self.room = [self.x, self.y-1]
    self.sensors[0] = self.room

like this

>>> a = []
>>> type(a)
<type 'list'>

>>> a[2,3]
Traceback (most recent call last):
File "<stdin>", line 1, in ?
TypeError: list indices must be integers

>>> a = [2,3]

回答5:

Why does it give that error? I'm not passing any tuples!

Because __getitem__, which deals with [] resolution, converts self.room[1, 2] to a tuple:

class C(object):
    def __getitem__(self, k):
        return k

# Single argument is passed directly.
assert C()[0] == 0

# Multiple indices generate a tuple.
assert C()[0, 1] == (0, 1)

and lists are not made to deal with such arguments.

More examples at: https://stackoverflow.com/a/33086813/895245