There are two issues here. The first is that the `data`

you pass to your function apparently isn’t a two-dimensional NumPy array — at least this is what the error message says.

The second issue is that the code does not do what you expect:

```
my_array = numpy.arange(9).reshape(3, 3)
# array([[0, 1, 2],
# [3, 4, 5],
# [6, 7, 8]])
temp = my_array[:, 0]
my_array[:, 0] = my_array[:, 1]
my_array[:, 1] = temp
# array([[1, 1, 2],
# [4, 4, 5],
# [7, 7, 8]])
```

The problem is that Numpy basic slicing does not create copies of the actual data, but rather a view to the same data. To make this work, you either have to copy explicitly

```
temp = numpy.copy(my_array[:, 0])
my_array[:, 0] = my_array[:, 1]
my_array[:, 1] = temp
```

or use advanced slicing

```
my_array[:, [0, 1]] = my_array[:, [1, 0]]
```