What python libraries will I need to be able to test systems data?

I am new to python and was hoping if you could kindly point my in the right direction?

Currently where I work they have a web based system that uses data from various other systems that is run through an algorithm and then displayed to users.

I would like to use python to test whether the system is fit for purpose by independently pulling data from several systems and then comparing this computed output against that of the system.

What libraries would I need to do this? I think I am trying to do Data-driven testing......

I have been doing a manual process using excel, but then the data is too large for Excel to handle and it is not an automated process.

Many Thanks

B