drop_duplicates not working in pandas?

Question

The purpose of my code is to import 2 Excel files, compare them, and print out the differences to a new Excel file.

However, after concatenating all the data, and us

Answer 1

If you have are using a DatetimeIndex in your DataFrame this will not work

df.drop_duplicates(subset=None, keep="first", inplace=True)

Instead one can use:

df = df[~df.index.duplicated()]