I want to do split a string using "},{" as the delimiter. I have tried various things but none of them work.

string="2,1,6,4,5,1},{8,1,4,9,6,6,7,0},{6,1,2,3,9},{2,3,5,4,3 "

Split it into something like this:

2,1,6,4,5,1
8,1,4,9,6,6,7,0
6,1,2,3,9
2,3,5,4,3

string.split("},{") works at the Python console but if I write a Python script in which do this operation it does not work.

You need to assign the result of string.split("},{") to a new string. For example:

string2 = string.split("},{")

I think that is the reason you think it works at the console but not in scripts. In the console it just prints out the return value, but in the script you want to make sure you use the returned value.