自定义函数应用map

def solve():
    import pandas as pd
    df = pd.read_csv('https://liangdaima.com/static/data/titanic.csv')
    def age_group(age):
        if pd.isna(age):
            return 'unknown'
        elif age < 18:
            return 'child'
        elif age < 60:
            return 'adult'
        else:
            return 'senior'
    groups = df['age'].map(age_group)
    print(sorted(groups.unique().tolist()))