how do change data in a database

[Larz60+]

Is it a bad use of pandas to load the data from a csv file, make modification to it and then save the modified data as a csv file

Not at all, and technically I guess you can call any accumulation of data a database.

The formal definition is:
a structured set of data held in a computer, especially one that is accessible in various ways.
"a database covering nine million workers"