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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def set_col_first(df, col_names):
 """set selected columns first in a pandas.DataFrame. This function sets cols with names given in col_names (a list) first in the DataFrame. The last col in col_name will come first (processed last) """


        column_headings = df.columns
        column_headings = column_headings.tolist()
        try:
            for col_name in col_names:
                i = column_headings.index(col_name)
                column_headings.pop(column_headings.index(col_name))
                column_headings.insert(0, col_name)

        finally:
            df = df.reindex(columns=column_headings)
            return df