Python :如何对dataframe中的行使用if elif

import pandas as pd

# 创建一个示例DataFrame
data = {'Name': ['Alice', 'Bob', 'Charlie', 'David'],
        'Age': [25, 30, 35, 40],
        'City': ['New York', 'London', 'Paris', 'Tokyo']}
df = pd.DataFrame(data)

# 定义一个函数，根据条件对行进行操作
def process_row(row):
    if row['Age'] < 30:
        row['Category'] = 'Young'
    elif row['Age'] < 40:
        row['Category'] = 'Middle-aged'
    else:
        row['Category'] = 'Old'
    return row

# 使用apply方法应用函数到每一行
df = df.apply(lambda row: process_row(row), axis=1)

# 打印处理后的DataFrame
print(df)

      Name  Age      City     Category
0    Alice   25  New York        Young
1      Bob   30    London  Middle-aged
2  Charlie   35     Paris  Middle-aged
3    David   40     Tokyo          Old