内连接merge

def solve():
    import pandas as pd
    df = pd.read_csv('https://liangdaima.com/static/data/titanic.csv')
    left = df[['pclass', 'sex', 'age']].head(10)
    right = df[['pclass', 'survived', 'fare']].head(10)
    result = pd.merge(left, right, on='pclass', how='inner')
    print(len(result))