Confusion re: pandas copy of slice of dataframe warning

 izmir = pd.read_excel(filepath) izmir_lim = izmir[['Gender','Age','MC_OLD_M>=60','MC_OLD_F>=60',                    'MC_OLD_M>18','MC_OLD_F>18','MC_OLD_18>M>5',                    'MC_OLD_18>F>5','MC_OLD_M_Child<5','MC_OLD_F_Child<5',                    'MC_OLD_M>0<=1','MC_OLD_F>0<=1','Date to Delivery',                    'Date to insert','Date of Entery']]

izmir_lim is a view/copy of izmir. You subsequently attempt to assign to it. This is what is throwing the error. Use this instead:

 izmir_lim = izmir[['Gender','Age','MC_OLD_M>=60','MC_OLD_F>=60',                    'MC_OLD_M>18','MC_OLD_F>18','MC_OLD_18>M>5',                    'MC_OLD_18>F>5','MC_OLD_M_Child<5','MC_OLD_F_Child<5',                    'MC_OLD_M>0<=1','MC_OLD_F>0<=1','Date to Delivery',                    'Date to insert','Date of Entery']].copy()

Whenever you 'create' a new dataframe from another in the following fashion:

new_df = old_df[list_of_columns_names]

new_df will have a truthy value in it's is_copy attribute. When you attempt to assign to it, pandas throws the SettingWithCopyWarning.

new_df.iloc[0, 0] = 1  # Should throw an error

You can overcome this in several ways.

Option #1

new_df = old_df[list_of_columns_names].copy()

Option #2 (as @ayhan suggested in comments)

new_df = old_df[list_of_columns_names]new_df.is_copy = None

Option #3

new_df = old_df.loc[:, list_of_columns_names]