题解 | #统计运动会项目报名人数(二)#

import pandas as pd
items = pd.read_csv('items.csv')
signup = pd.read_csv('signup.csv')
merge_si = pd.merge(items,signup,how='left',on='item_id')
res = merge_si.groupby(['item_name']).name.count().fillna(0)
print(res)