Python Pandas giving me SettingWithCopyWarning when I attempt to map a particular DataFrame column - how to fix? I have some code that needs to replace two columns of a pandas DataFrame with the index of each value as they appear in a unique list of those values. For example: col1, col2, col3, col4 A, 1, 2, 3 A, 1, 2, 3 B, 1, 2, 3 Should end up in the data frame as: col1, col2, col3, col4 0, 1, 2, 3 0, 1, 2, 3 1, 1, 2, 3 since A is element 0 in the list of unique col1 values, and B is element number 1. What I did is: unique_vals = df['col1'].unique() # create a map to speed up looking indexes when we...