[ Python 常見問題 ] How to send email attachments with Python

Source From Here 
Question 
I am having problems understanding how to email an attachment using Python. I have successfully emailed simple messages with the smtplib. Could someone please explain how to send an attachment in an email. I know there are other posts online but as a Python beginner I find them hard to understand. 

How-To 
Here's another, adapted from here: 

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1. import smtplib  
2. from os.path import basename  
3. from email.mime.application import MIMEApplication  
4. from email.mime.multipart import MIMEMultipart  
5. from email.mime.text import MIMEText  
6. from email.utils import COMMASPACE, formatdate  
7.   
8.   
9. def send_mail(send_from, send_to, subject, text, files=None,  
10.               server="127.0.0.1"):  
11.     assert isinstance(send_to, list)  
12.   
13.     msg = MIMEMultipart()  
14.     msg['From'] = send_from  
15.     msg['To'] = COMMASPACE.join(send_to)  
16.     msg['Date'] = formatdate(localtime=True)  
17.     msg['Subject'] = subject  
18.   
19.     msg.attach(MIMEText(text))  
20.   
21.     for f in files or []:  
22.         with open(f, "rb") as fil:  
23.             part = MIMEApplication(  
24.                 fil.read(),  
25.                 Name=basename(f)  
26.             )  
27.             part['Content-Disposition'] = 'attachment; filename="%s"' % basename(f)  
28.             msg.attach(part)  
29.   
30.   
31.     smtp = smtplib.SMTP(server)  
32.     smtp.sendmail(send_from, send_to, msg.as_string())  
33.     smtp.close()