使用smtplib的sendmail发送邮件时触发list indices类型错误

运行以下Python代码时，登录操作成功，且已成功从info.xlsx文件中获取邮箱数据，但发送邮件时出现错误，异常信息为：

list indices must be integers or slices, not str

原代码 #

from asyncio import constants
import pandas as pd
import smtplib as smt
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from getpass import getpass

print("Reading mails from Excel")
data = pd.read_excel("info.xlsx")
emailData = data.get("Email")
emailList = list(emailData)

try:
    # SMTP Object
    print("In process...")
    mailServer = smt.SMTP("smtp.gmail.com", 587)
    mailServer.starttls()
    # Inputting email and password
    senderMail = input("Enter your Email address: ")
    senderPass = getpass("Input your password: ")
    # Setting up the email subject, to, from, and message
    fromEmail = senderMail
    toEmail = emailList
    Emailmessage = MIMEMultipart("alternative")
    Emailmessage['Subject'] = "Testing for Python Project"
    Emailmessage['from'] = senderMail

    # Creating the text via HTML
    messageHTML = '''
    <html>
        <head>
            <style>
                .btn{
                  background:red;
                }
            </style>
        </head>
        <body>
            <h1>HEading 1</h1>
            <button id="btn">Test</button>
        </body>
    </html>
    '''

    # login via email
    mailServer.login(senderMail, senderPass)
    print("Login Successful")

    # Attach the message and Multipart
    textMsg = MIMEText(messageHTML, "html")
    Emailmessage.attach(textMsg)

    # Sending the email
    mailServer.sendmail(fromEmail, toEmail, Emailmessage.as_string())

    for email in emailList:
        print("Message has been sent to ", emailList[email])

    mailServer.quit()


except Exception as error:
    print(error)

错误原因及修复方法 #

错误并非来自sendmail的第三个参数，而是出在循环打印的代码段：

for email in emailList:
    print("Message has been sent to ", emailList[email])

这里email是emailList中的字符串元素（比如xxx@example.com），但列表只能用整数或切片作为索引，用字符串索引自然会抛出list indices must be integers or slices, not str的错误。

修复步骤：

1. 修改循环打印代码，直接使用遍历到的email变量：

for email in emailList:
    print("Message has been sent to ", email)

2. 可选优化：给邮件对象添加to字段，让邮件头部信息更完整：

Emailmessage['to'] = ', '.join(emailList)

额外注意事项

如果后续使用Gmail登录失败，需要注意：

• Gmail默认禁用普通密码登录SMTP，需开启两步验证后生成应用专用密码，用该密码替代普通密码登录。

内容的提问来源于stack exchange，提问作者Abhi