mysqldump命令在cmd中工作，但在python中不起作用

import subprocess

# 指定mysqldump命令的绝对路径
mysqldump_path = "C:/path/to/mysqldump.exe"

# 执行mysqldump命令
subprocess.call([mysqldump_path, "--user=username", "--password=password", "database_name", ">", "backup.sql"])

import mysql.connector

# 连接到MySQL数据库
cnx = mysql.connector.connect(user='username', password='password', host='localhost', database='database_name')

# 创建游标对象
cursor = cnx.cursor()

# 执行SQL查询语句
query = "SELECT * FROM table_name"
cursor.execute(query)

# 将查询结果写入文件
with open('backup.sql', 'w') as f:
    for row in cursor:
        f.write(','.join(str(col) for col in row) + '\n')

# 关闭游标和数据库连接
cursor.close()
cnx.close()