Insert a column to a pandas dataframe

Question

Scenario: I have a code that reads data from excel worksheets into dataframes, merges into one dataframe, and perform some cleaning procedures.

Answer 1

You could also append it to the end of the dataframe (the order of the columns generally shouldn't matter except for presentation purposes).

fnl = fnl.assign(N=15)

This returns a copy of the dataframe with the new column N added with values equal to 15.

Because the index doesn't matter in this case, it should be more efficient to append via:

fnl['N'] = 15