def series2cat(df:DataFrame, *col_names):
    "Categorifies the columns `col_names` in `df`."
    for c in listify(col_names): df[c] = df[c].astype('category').cat.as_ordered()
def series2cat ( df : DataFrame , * col_names ) : for c in listify ( col_names ) : df [ c ] = df [ c ] . astype ( 'category' ) . cat . as_ordered ( )
Categorifies the columns `col_names` in `df`.