LibreOffice is a free office suite that's an alternative to MS Office and other office packages. It includes a text editor and a spreadsheet program called Calc. Calc understands the regular Excel formats, and it's also totally scriptable internally through its UNO API. The UNO interface allows programmatic access to the suite, and it's accessible in different languages, such as Java.
One of the available language is Python, making it very easy to generate very complex applications in a suite format, as this enables the use of the full Python standard library.
Using the full Python standard library give access to elements such as cryptography; opening external files, including ZIP files; or connecting to remote databases. Also, take advantage of the Python syntax and avoid dealing with LibreOffice BASIC.
We'll see in this recipe...