KAWA GORDON สอนนักเรียนกี่คน
How many students does KAWA GORDON teaches?
df_list = pd.DataFrame(columns=['classroom']); df_teachers = pd.DataFrame(columns=['classroom', 'firstname', 'lastname'])
len(df_list[df_list['classroom'].isin(df_teachers[(df_teachers['firstname'] == 'KAWA') & (df_teachers['lastname'] == 'GORDON')]['classroom'])])