如何在使用python 3发送邮件前重写邮件正文？

import smtplib
from email.mime.text import MIMEText
from email.header import Header

# 创建一个MIMEText对象，参数为邮件正文内容和邮件类型（plain表示纯文本）
text = MIMEText('这是邮件正文内容', 'plain', 'utf-8')

text['Subject'] = Header('邮件主题', 'utf-8')
text['From'] = '发件人邮箱'
text['To'] = '收件人邮箱'

# 连接SMTP服务器
smtp_server = 'SMTP服务器地址'
smtp_port = 'SMTP服务器端口'
smtp_username = '发件人邮箱'
smtp_password = '发件人邮箱密码'

server = smtplib.SMTP(smtp_server, smtp_port)
server.login(smtp_username, smtp_password)

# 发送邮件
server.sendmail(smtp_username, [text['To']], text.as_string())

# 关闭连接
server.quit()

import smtplib
from email.mime.text import MIMEText
from email.header import Header

def send_email(subject, content, sender, receiver, smtp_server, smtp_port, smtp_username, smtp_password):
    # 创建一个MIMEText对象，参数为邮件正文内容和邮件类型（plain表示纯文本）
    text = MIMEText(content, 'plain', 'utf-8')
    text['Subject'] = Header(subject, 'utf-8')
    text['From'] = sender
    text['To'] = receiver

    # 连接SMTP服务器
    server = smtplib.SMTP(smtp_server, smtp_port)
    server.login(smtp_username, smtp_password)

    # 发送邮件
    server.sendmail(sender, [receiver], text.as_string())

    # 关闭连接
    server.quit()

# 示例用法
subject = '邮件主题'
content = '这是邮件正文内容'
sender = '发件人邮箱'
receiver = '收件人邮箱'
smtp_server = 'SMTP服务器地址'
smtp_port = 'SMTP服务器端口'
smtp_username = '发件人邮箱'
smtp_password = '发件人邮箱密码'

send_email(subject, content, sender, receiver, smtp_server, smtp_port, smtp_username, smtp_password)