เมืองใดที่จัดงานมากที่สุด?
Which city has hosted the most events?
df_city = pd.DataFrame(columns=['city', 'city_id']); df_host_city = pd.DataFrame(columns=['host_city'])
df_city[df_city['city_id'].isin(df_host_city['host_city'])]['city'].value_counts().idxmax()