Python, Pandas To Add Columns From Calculation

A data frame like this and I am adding some columns from mapping and calculation. code month of entry name reports 0 JJ 20171002 Jason 14 1 MM 201712

Solution 1:

You need copy:

df1 = df[df['name_code'].isin(wanted)].copy()

If you modify values in df1 later you will find that the modifications do not propagate back to the original data (df), and that Pandas does warning.