send_xlsx.py

# -*- coding: utf-8 -*-
from email import encoders
from email.header import Header
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart  
from email.utils import parseaddr, formataddr
import smtplib
import os

def _format_addr(s):
	name, addr = parseaddr(s)
	return formataddr(( \
		Header(name, 'utf-8').encode(), \
		addr.encode('utf-8') if isinstance(addr, unicode) else addr))

def main():	
	from_addr = 'your@qq.com'
	to_addr = 'her@qq.com'
	password = 'xxxxxx'
	smtp_server = 'smtp.qq.com'
	base_dir = os.path.dirname(__file__)
	attach_dir = unicode(os.path.join(base_dir, 'attachment_file\\'),'mbcs')
	
	server = smtplib.SMTP(smtp_server, 25)
	server.login(from_addr, password)
	
	msg = MIMEMultipart()
	msg.set_charset('utf8')
	msg.attach(MIMEText(u'邮件正文','plain','utf-8'))
	msg['From'] = _format_addr(u'发件人名 <%s>' % from_addr) # 发件人地址
	
	attach_file = u'报表.xlsx'
	attach_filedir = os.path.join(attach_dir, attach_file)
	attach_file = attach_file.encode('gbk','ignore')
	
	msg['To'] = _format_addr(u'收件人 <%s>' % to_addr) # 收件人地址
	msg['Subject'] = Header(u'报表.xlsx', 'utf-8').encode()  # 邮件主题=附件文件名
	mime = MIMEText(open(attach_filedir, 'rb').read(),'base64','utf-8')
	mime.add_header('Content-Disposition', 'attachment', filename = attach_file)
	mime.add_header('Content-Type', 'application/octet-stream')
	msg.attach(mime)
	
	server.sendmail(from_addr, to_addr, msg.as_string())

if __name__ == '__main__':
		main()

python3.5 win7， mime.add_header('Content-Disposition', 'attachment', filename = attach_file)
if attach_file= attach_file.encode('gbk', 'ignore')，
Error AttributeError: 'bytes' object has no attribute 'encode'
why????Thanks