ชื่อประเทศอะไรพูดได้ทั้งภาษาอังกฤษและฝรั่งเศส?
What are the names of nations speak both English and French?
country = pd.DataFrame(columns=['Name', 'Code']); countrylanguage = pd.DataFrame(columns=['CountryCode', 'Language'])
country[country['Code'].isin(countrylanguage[countrylanguage['Language'] == 'English']['CountryCode']) & country['Code'].isin(countrylanguage[countrylanguage['Language'] == 'French']['CountryCode'])]['Name'].unique()