如何从pandas中基于if-else条件的元组索引中提取字符串？

import pandas as pd

# 创建一个示例DataFrame
data = {
    'tuples': [('apple', 'fruit'), ('carrot', 'vegetable'), ('banana', 'fruit')]
}
df = pd.DataFrame(data)

# 定义一个函数，根据条件从元组中提取字符串
def extract_string(row):
    if row[1] == 'fruit':
        return row[0]
    else:
        return None

# 使用apply函数应用自定义函数
df['extracted'] = df['tuples'].apply(extract_string)

print(df)

          tuples extracted
0     (apple, fruit)    apple
1  (carrot, vegetable)     None
2    (banana, fruit)   banana