题解 | #统计运动会项目报名人数(二)#

import pandas as pd 
import numpy as np 

# 1.读取数据
items = pd.read_csv('items.csv', encoding='utf8')
signup = pd.read_csv('signup.csv', encoding='utf8')

# 2. 合并表
data = pd.merge(left=items, right=signup, on='item_id', how='outer')

# 3. 保留数据
data = data[['item_name', 'item_id']]

# 4. 分组
data = data.groupby(by=['item_name'])['item_id'].count()
print(data)