题解 | #统计运动会项目报名人数#

import pandas as pd
import numpy as np

items = pd.read_csv("items.csv", sep=",")
signup = pd.read_csv("signup.csv", sep=",")
merged = pd.merge(
    items,
    signup,
    how="inner",
    on="item_id",
    left_on=None,
    right_on=None,
    left_index=False,
    right_index=False,
    sort=True,
    suffixes=("_x", "_y"),
    copy=True,
)
print(merged[merged["item_id"].notnull() == True].groupby("item_name")['employee_id'].count())