When working with more data than can fit in an Excel file, or when you want to be sure the data won't be edited, you usually need to interact with the data by writing scripts.
One of the biggest time sinks (for me) when working with these tools (ACL, SQL, Python) is debugging, and working out exactly where in the chain of individual commands something unexpected happened. Even with only a modest page of code, I can quickly find myself rerunning the entire script multiple times and commenting-out and uncommenting multiple lines in order to understand what's really going on. If you have a time consuming task at the start of your script, such as a summarise and sort command, the extra time required can be even greater. This leads to interrupted flow and concentration.
Pandas is a python package to manipulate large datasets, the Jupyter notebook is an application which allows the user to run a python script in chunks, and output the results of each chunk before continuing. You can re-run a previous chunk without returning to the beginning, and change the code as you go along. This is amazingly flexible and intuitive.
I recently worked through an exceptionally good Pandas tutorial recorded at PyCon 2015. "Pandas from the ground up" is well structured, clear, has good scope and the resources are available to download from github. Brandon Rhodes gives you a good working foundation for using Pandas and the Jupyter notebook to manipulate datasets using Python.