How to use Python with a database?

I wrote a Python program that processes very large data. As the data is processed, it turns the processed data into an array that easily grows to hundreds of megabytes or even over a gigabyte.

I installed it like this because Python must constantly access the data in the array. As the array grows larger and larger, the process is easily error prone and very slow.

Is there a way to have a massive database stored in another file or database module and access it as needed?

This may be a very simple task, but I have no idea.