'str' object does not support item assignment

[MRAB]

On 2012-09-23 19:31, jimbo1qaz wrote:
> spots[y][x]=mark fails with a "'str' object does not support item assignment" error,even though:
>>>> a=[["a"]]
>>>> a[0][0]="b"
> and:
>>>> a=[["a"]]
>>>> a[0][0]=1000000
> both work.
> Spots is a nested list created as a copy of another list.
>
The error suggests that spots[y] is actually a string. Printing
repr(spots) and repr(spots[y]) should tell you whether it is.