使用Python发送CSV邮件附件时遇'list'对象无encode属性错误求助

错误原因分析 #

1. 收件人格式不兼容：read_managers_email()返回的是邮箱列表，但EmailMessage的To字段需要传入逗号分隔的字符串，直接赋值列表会触发编码错误。
2. 附件处理方式错误：
   • 读取CSV文件用了文本模式'r'，但二进制附件需要用二进制模式'rb'读取；
   • 混用MIMEApplication和EmailMessage的attach方法，容易出现格式兼容问题，EmailMessage推荐用自身的add_attachment方法添加附件。

修正后的代码 #

import os
import smtplib
from email.message import EmailMessage

def send_csv():
    csv_file = check_consumable_status()
    if csv_file:
        mail_server = log_in_mail_server()
        recipients = read_managers_email()
        notification_email = create_notification_email(csv_file)
        if send_email(mail_server, notification_email, recipients):
            print("Mail sent")
    else:
        print("Unable to read subscription status")
        return

def create_notification_email(csv):
    notification_email = EmailMessage()
    notification_email['Subject'] = "consumable notification"
    notification_email['From'] = os.environ["EMAIL_USER"]

    # 用二进制模式读取文件，适配附件要求
    with open('consumable_notification.csv', 'rb') as file:
        # 使用EmailMessage原生的add_attachment方法，更简洁兼容
        notification_email.add_attachment(
            file.read(),
            maintype='application',
            subtype='octet-stream',
            filename='consumable_notification.csv'
        )

    return notification_email

def send_email(server, email, to_address):
    try:
        # 将邮箱列表转为逗号分隔的字符串，适配EmailMessage的To字段要求
        email['To'] = ', '.join(to_address)
        server.send_message(email)
        return True
    except Exception as e:
        print("Failed to send email")
        print(e)
        return False

def log_in_mail_server():
    SERVER = os.environ["EMAIL_SERVER"]
    PORT = int(os.environ["EMAIL_PORT"])  # 转换为整数，避免端口类型错误
    try:
        server = smtplib.SMTP(SERVER, PORT)
        server.ehlo()
        server.starttls()
        server.ehlo()
        user = os.environ["EMAIL_USER"]
        password = os.environ["EMAIL_PASSWORD"]
        server.login(user, password)
        print("Successfully log in to server")
        return server
    except Exception as e:
        print("Failed to log in to server")
        print(e)
        return False

关键修改点说明 #

• 收件人处理：用', '.join(to_address)将邮箱列表转为符合邮件标准的字符串格式；
• 附件读取：把文件打开模式从'r'改为'rb'，确保读取二进制数据；
• 附件添加：改用EmailMessage.add_attachment()方法，参数更清晰，避免MIME类和EmailMessage的兼容问题；
• 端口转换：添加int(os.environ["EMAIL_PORT"])，确保端口是整数类型，避免连接错误。

内容的提问来源于stack exchange，提问作者tjarne