外连接merge

def solve():
    import pandas as pd
    df = pd.read_csv('https://liangdaima.com/static/data/titanic.csv')
    left = df[['pclass', 'sex']].head(8)
    right = df[['pclass', 'age']].iloc[5:15]
    result = pd.merge(left, right, on='pclass', how='outer')
    print(len(result))