任何人都可以告诉我为什么我收到错误[AttributeError：'list'对象没有属性'encode']

I keep trying to run this code in order to send an excel sheet as an attachment on an email. I can send normal emails using smtplib but can't get the MIMEMultipart to work. I keep getting the [AttributeError: 'list' object has no attribute 'encode'] error I keep trying to run this code in order to send