We are all travelers in the wilderness of this world, and the best we can find in our travels is an honest friend. Those good old lovely days are the starlight that guides me on my way forward. However, we never go back.

Selected answers:

• Rename MultiIndex columns in Pandas
• Add a column to a multiindex column dataframe
• Returning multiple variables with pandas.series.apply
• Truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all()
• Adding total to bottom of each multiindex group
• pandas.Series method that returns updated series