I have a list of 2 by n arrays of x and y coordinates. 

```
old: [array([[1, 2, 3], [4, 5, 6]]), array([[10, 20, 30], [40, 50, 60]])]

```

I am trying to shift the y-coordinates, the second row of each array, by a certain value 'shift'. However, when I try to do this by the method below, I get the an error: 

> 
> "TypeError: list indices must be integers, not tuple when trying to alter certain elements of a list of arrays."
> 
> 
> 

```
import pylab

    def shiftY(old,shift):
        new = list([])

        for i in arange(len(old)):
            y = old[i][1,:] + shift
            newItem = array([old[:,0],y])
            new.append(newItem)

        return new

    old = list()
    old.append(arr

ay([[1, 2, 3], [4, 5, 6]]))
old.append(array([[10,20,30],[40,50,60]]))
shift =3 
new=shiftY(old,shift)
print(new)

```

Traceback:

```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27_32bit\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 540, in runfile
    execfile(filename, namespace)
  File "C:/Users/tald574/testShifty.py", line 25, in <module>
    new=shiftY(old,shift)
  File "C:/Users/tald574/testShifty.py", line 15, in shiftY
    newItem = array([old[:,0],y])
TypeError: list indices must be integers, not tuple

```

I can't see what I am doing wrong as `newItem` is not even supposed to be a list, it should be a 2D array. Would appreciate it if someone can tell me what I do wrong an how to fix it.

Thanks.

Edit:
The expected outcome of this test would be,

```
new:[array([[1, 2, 3], [7, 8, 9]]), array([[10, 20, 30], [43, 53, 63]])]

```