join索引连接

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