如果我的文件中缺少特定字符串，如何通过python发送电子邮件警报？

import smtplib

def send_email_alert():
    # 读取文件内容
    with open('your_file.txt', 'r') as file:
        content = file.read()

    # 检查特定字符串是否存在
    if 'specific_string' not in content:
        # 发送邮件
        sender_email = 'your_email@example.com'
        receiver_email = 'recipient_email@example.com'
        subject = 'Alert: Specific string is missing in file'
        body = 'The specific string is missing in the file.'

        # 创建SMTP对象并登录到发件人邮箱
        smtp_obj = smtplib.SMTP('smtp.example.com', 587)
        smtp_obj.starttls()
        smtp_obj.login('your_email@example.com', 'your_password')

        # 发送邮件
        message = f'Subject: {subject}\n\n{body}'
        smtp_obj.sendmail(sender_email, receiver_email, message)

        # 关闭SMTP连接
        smtp_obj.quit()

# 调用函数发送邮件警报
send_email_alert()