add excel file attachment when sending python email

How do i add a document attachment when sending an email with python ? i get the email to send (please ignore: i am looping the email to send every 5 seconds, only for testing purposes, i want it to send every 30 min, just have to change 5 to 1800)

here is my code so far. how do i attach a document from my computer?

#!/usr/bin/python

import time
import smtplib

while True:
    TO = 'xxxx@gmail.com'
    SUBJECT = 'Python Email'
    TEXT = 'Here is the message'

    gmail_sender = 'xxxx@gmail.com'
    gmail_passwd = 'xxxx'

    server = smtplib.SMTP('smtp.gmail.com',587)
    server.ehlo()
    server.starttls()
    server.ehlo()
    server.login(gmail_sender, gmail_passwd)
    BODY = '\n'.join([
        'To: %s' % TO,
        'From: %s' % gmail_sender,
        'Subject:%s' % SUBJECT,
        '',
        TEXT

        ])

    try:
        server.sendmail(gmail_sender,[TO], BODY)
        print 'email sent'
    except:
        print 'error sending mail'

    time.sleep(5)

server.quit()

This is the code that worked for me- to send an email with an attachment in python

#!/usr/bin/python
import smtplib,ssl
from email.mime.multipart import MIMEMultipart
from email.mime.base import MIMEBase
from email.mime.text import MIMEText
from email.utils import formatdate
from email import encoders

def send_mail(send_from,send_to,subject,text,files,server,port,username='',password='',isTls=True):
    msg = MIMEMultipart()
    msg['From'] = send_from
    msg['To'] = send_to
    msg['Date'] = formatdate(localtime = True)
    msg['Subject'] = subject
    msg.attach(MIMEText(text))

    part = MIMEBase('application', "octet-stream")
    part.set_payload(open("WorkBook3.xlsx", "rb").read())
    encoders.encode_base64(part)
    part.add_header('Content-Disposition', 'attachment; filename="WorkBook3.xlsx"')
    msg.attach(part)

    #context = ssl.SSLContext(ssl.PROTOCOL_SSLv3)
    #SSL connection only working on Python 3+
    smtp = smtplib.SMTP(server, port)
    if isTls:
        smtp.starttls()
    smtp.login(username,password)
    smtp.sendmail(send_from, send_to, msg.as_string())
    smtp.quit()