I have found a solution:
import pandas as pd data1 = pd.read_csv('eurogold.csv',index_col=0) data2 = pd.read_csv('woo.csv', index_col=0) df1 = pd.DataFrame(data1) print ('stampa df1') df1 = df1.drop_duplicates(['codbar']) # elimina duplicati df1['codbar'] = df1['codbar'].astype(str) print(df1) df2 = pd.DataFrame(data2) df2 = df2.dropna().reset_index(drop=True) print ('stampa df2') print(df2) mask = df2.sku.isin(df1.codbar.values) df2.loc[mask, 'stock_quantity'] = '0' df2.loc[mask, 'stock_status'] = 'outofstock' print(df2) df2.to_csv('risultato.csv')