如何从CSV文件中替换python中的字符串的一部分？

import csv

def replace_string(csv_file, search_str, replace_str):
    with open(csv_file, 'r', newline='') as file:
        reader = csv.reader(file)
        rows = list(reader)
        
        for row in rows:
            for i, cell in enumerate(row):
                if isinstance(cell, str) and search_str in cell:
                    row[i] = cell.replace(search_str, replace_str)
    
    with open(csv_file, 'w', newline='') as file:
        writer = csv.writer(file)
        writer.writerows(rows)

# 示例用法
csv_file = 'data.csv'  # CSV文件路径
search_str = 'old_text'  # 要搜索的字符串
replace_str = 'new_text'  # 要替换的字符串

replace_string(csv_file, search_str, replace_str)