[Zope] string to list?

Hello, I have a Z SQL method which returns me a string like {{"a"},{"b"},{"c"}} Is there anyway I can write a dtml-in loop to pick out each element from the string? I want to be able to do something like: <dtml-in my_zsql_method_which_returns_a_string> <dtml-var element>, </dtml-in> and that should give me "a,b,c". Is this possible? Or do I need to write an external python method to return a list["a", "b", "c"] given the string above? Thanks! nitesh