Detailed explanation of the use of smtplib module in Python to process emails_Basic knowledge

In Internet-based applications, programs often need to automatically send emails. For example: the registration system of a website will send an email to confirm the registration when the user registers; when the user forgets the login password, the user will retrieve the password through email. The smtplib module is a client implementation of SMTP (Simple Mail Transfer Protocol) in Python. We can use the smtplib module to send emails easily. The following example sends an email in less than ten lines of code:

#coding=gbk 
 
import smtplib 
 
smtp = smtplib.SMTP() 
smtp.connect("smtp.yeah.net", "25") 
smtp.login('用户名', '密码') 
smtp.sendmail('from@yeah.net', 'to@21cn.com', 'From: from@yeah.net/r/nTo: to@21cn.com/r/nSubject: this is a email from python demo/r/n/r/nJust for test~_~') 
smtp.quit()

This example is simple enough^_^! The classes and methods in the stmplib module are introduced in detail below.
smtplib.SMTP([host[, port[, local_hostname[, timeout]]]])

The SMTP class constructor represents the connection with the SMTP server. Through this connection, we can send instructions to the SMTP server and perform related operations (such as logging in, sending emails). This class provides a number of methods, which are described below. All its parameters are optional. The host parameter represents the host name of the SMTP server. The SMTP host in the above example is "smtp.yeah.net"; port represents the port of the SMTP service. The default is 25; if you are creating an SMTP object These two parameters are provided during initialization, and the connect method will be automatically called to connect to the server during initialization.

The smtplib module also provides the SMTP_SSL class and LMTP class, and their operations are basically the same as SMTP.

Methods provided by smtplib.SMTP:

SMTP.set_debuglevel(level)

Set whether it is debug mode. The default is False, which is non-debugging mode, which means no debugging information will be output.

SMTP.connect([host[, port]])

Connect to the specified smtp server. The parameters represent the smpt host and port respectively. Note: You can also specify the port number in the host parameter (eg: smpt.yeah.net:25), so there is no need to give the port parameter.

SMTP.docmd(cmd[, argstring])

Send instructions to the smtp server. The optional parameter argstring represents the parameters of the instruction. The following example completely implements email sending by calling the docmd method to send instructions to the server (tested on the smtp.yeah.net mail server. It has not been tried on other mail servers):

import smtplib, base64, time 
userName = base64.encodestring('from').strip() 
password = base64.encodestring('password').strip() 
smtp = smtplib.SMTP() 
smtp.connect("smtp.yeah.net:25") 
print smtp.docmd('helo', 'from') 
print smtp.docmd('auth login') 
print smtp.docmd(userName) 
print smtp.docmd(password) 
print smtp.docmd('mail from:', '<from@yeah.net>') 
print smtp.docmd('rcpt to:', '<from@yeah.net>') 
#data 指令表示邮件内容 
print smtp.docmd('data') 
print smtp.docmd(
'''''from: from@yeah.net 
to: from@yeah.net 
subject: subject 
email body 
. 
'''
) 
smtp.quit()

SMTP.helo([hostname])

Use the "helo" command to confirm identity to the server. It is equivalent to telling the SMTP server "who I am".
SMTP.has_extn(name)

Determine whether the specified name exists in the server mailing list. For security reasons, SMTP servers often block this command.
SMTP.verify(address)

Determine whether the specified email address exists in the server. For security reasons, SMTP servers often block this command.
SMTP.login(user, password)

Log in to the smtp server. Almost all SMTP servers now must verify that the user information is legitimate before allowing emails to be sent.
SMTP.sendmail(from_addr, to_addrs, msg[, mail_options, rcpt_options])

Send email. Pay attention to the third parameter here. msg is a string representing an email. We know that emails generally consist of a title, sender, recipient, email content, attachments, etc. When sending an email, pay attention to the format of msg. This format is the format defined in the smtp protocol. In the above example, the value of msg is:

'''''From: from@yeah.net 
To: to@21cn.com 
Subject: test 
 
just for test'''

The meaning of this string is that the email sender is "from@yeah.net", the recipient is "to@21cn.com", the email title is "test", and the email content is "just for test". If you are careful, you may wonder: If the content of the email to be sent is very complex, including pictures, videos, attachments, etc., it will be very troublesome to splice strings according to the MIME format. Don't worry, Python has already taken this into consideration. It provides us with an email module, which can be used to easily send emails with complex content such as pictures, videos, attachments, etc. After introducing the smtplib module, I will briefly introduce the basic use of the email module.
SMTP.quit()

Disconnecting from the smtp server is equivalent to sending the "quit" command.
email and its related sub-modules

The emial module is used to process email messages, including MIME and other message documents based on RFC 2822. It is very simple to use these modules to define the content of emails. Here are some commonly used classes:

• class email.mime.multipart. MIMEMultipart: A collection of multiple MIME objects.
• class email.mime.audio. MIMEAudio: MIME audio object.
• class email.mime.image. MIMEImage: MIME binary file object.
• class email.mime.text. MIMEText: MIME text object.

The above explanation may seem confusing. In fact, my understanding of SMTP and MIME is also very superficial. But most of the time, we just need to know how to use it. Here is a simple example to demonstrate how to use these classes to send emails with attachments:

#coding=gbk 
import smtplib, mimetypes 
from email.mime.text import MIMEText 
from email.mime.multipart import MIMEMultipart 
from email.mime.image import MIMEImage 
 
msg = MIMEMultipart() 
msg['From'] = "from@yeah.net" 
msg['To'] = 'to@21cn.com' 
msg['Subject'] = 'email for tesing' 
 
#添加邮件内容 
txt = MIMEText("这是邮件内容~~") 
msg.attach(txt) 
 
#添加二进制附件 
fileName = r'e:/PyQt4.rar' 
ctype, encoding = mimetypes.guess_type(fileName) 
if ctype is None or encoding is not None: 
 ctype = 'application/octet-stream' 
maintype, subtype = ctype.split('/', 1) 
att1 = MIMEImage((lambda f: (f.read(), f.close()))(open(fileName, 'rb'))[0], _subtype = subtype) 
att1.add_header('Content-Disposition', 'attachment', filename = fileName) 
msg.attach(att1) 
 
#发送邮件 
smtp = smtplib.SMTP() 
smtp.connect('smtp.yeah.net:25') 
smtp.login('from', '密码') 
smtp.sendmail('from@yeah.net', 'to@21cn.com', msg.as_string()) 
smtp.quit() 
print '邮件发送成功'

Isn’t it very simple? Simplicity is beautiful, solving problems with the least amount of code, this is Python. For more information about smtplib, please refer to the Python manual smtplib module .