1. Are familiar with Python.
2. Have Excel files with data.
3. Know Excel isn’t quite the best tool for working with data.
Then the wonderful xlrd and xlwt modules can help you extract values from .xls workbooks, iterating with rows and columns. They also allow you to write Excel files, no MS Office or LibreOffice Calc involved. Their documentation can be downloaded here. I’ve also made a gist with two functions for reading and writing Excel files to and from numpy’s ndarrays. They are quite straightfoward and don’t do any type conversion, so feel free to modify them as you see fit.