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pythonpandasvalueerror

I'm getting the following error message: ValueError: cannot reindex from a duplicate axis

Why am I getting this error message? My code:

my_df.loc[my_df['col1'] < my_df['col2'],'col3'] = my_df['col1'].

Basically what I'm trying to do is set col3 equal to col1 whenever col3 is less than col2. Thanks!

Solution

  • I solved this by resetting the index on the dataframes with reset_index(). The index got "messed up" due to a prior concat function.