Is there any field that can store a Python list(not as a string)? If not, is there any way I can store a list inside a field without typecasting it to string or any other data type?
You can use a dict field for that. But instead of a list, you will get a JSON-dictionary. See http://docs.tryton.org/projects/server/en/latest/ref/models/fields.html#dict and http://docs.tryton.org/projects/server/en/latest/ref/models/models.html#dictschemamixin for more information. You can also take a look at the product_attributes module how it can be implemented.
For now, we do not have such field. But it is a feature requested: Add MultiSelection field (#7851) · Issues · Tryton / Tryton · GitLab
I will try to use Dict and see what happens