Foundations of Python Network Programming 978-1-4302-3004-5

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CHAPTER 12 ■ E-MAIL COMPOSITION AND DECODING The program is simple. It creates a Message object, sets the headers and body, and prints the result. When you run this program, you will get a nice formatted message with proper headers. The output is suitable for transmission right away! You can see the result in Listing 12–3. Listing 12–3. Printing the E-mail to the Screen $ ./trad_gen_simple.py To: recipient@example.com From: Test Sender Subject: Test Message, Chapter 12 Hello, This is a test message from Chapter 12. I hope you enjoy it! -- Anonymous While technically correct, this message is actually a bit deficient when it comes to providing enough headers to really function in the modern world. For one thing, most e-mails should have a Date header, in a format specific to e-mail messages. Python provides an email.utils.formatdate() routine that will generate dates in the right format. You should add a Message-ID header to messages. This header should be generated in such a way that no other e-mail, anywhere in history, will ever have the same Message-ID. This might sound difficult, but Python provides a function to help do that as well: email.utils.make_msgid(). So take a look at Listing 12–4, which fleshes out our first sample program into a more complete example that sets these additional headers. Listing 12–4. Generating a More Complete Set of Headers #!/usr/bin/env python # Foundations of Python Network Programming - Chapter 12 - trad_gen_newhdrs.py # Traditional Message Generation with Date and Message-ID # This program requires Python 2.5 or above import email.utils from email.message import Message message = """Hello, This is a test message from Chapter 12. I hope you enjoy it! -- Anonymous""" msg = Message() msg['To'] = 'recipient@example.com' msg['From'] = 'Test Sender ' msg['Subject'] = 'Test Message, Chapter 12' msg['Date'] = email.utils.formatdate(localtime = 1) msg['Message-ID'] = email.utils.make_msgid() msg.set_payload(message) print msg.as_string() That’s better! If you run the program, you will notice two new headers in the output, as shown in Listing 12–5. 201
CHAPTER 12 ■ E-MAIL COMPOSITION AND DECODING Listing 12–5. A More Complete E-mail Is Printed Out $ ./trad_gen_newhdrs.py To: recipient@example.com From: Test Sender Subject: Test Message, Chapter 12 Date: Mon, 02 Aug 2010 10:05:55 -0400 Message-ID: Hello, This is a test message from Chapter 12. I hope you enjoy it! -- Anonymous The message is now ready to send! You might be curious how the unique Message-ID is created. It is generated by adhering to a set of loose guidelines. The part to the right of the @ is the full hostname of the machine that is generating the e-mail message; this helps prevent the message ID from being the same as the IDs generated on entirely different computers. The part on the left is typically generated using a combination of the date, time, the process ID of the program generating the message, and some random data. This combination of data tends to work well in practice in making sure every message can be uniquely identified. Parsing Traditional Messages So those are the basics of creating a plain e-mail message. But what happens when you receive an incoming message as a raw block of text and want to look inside? Well, the email module also provides support for parsing e-mail messages, re-constructing the same Message object that would have been used to create the message in the first place. (Of course, it does not matter whether the e-mail you are parsing was originally created in Python through the Message class, or whether some other e-mail program created it; the format is standard, so Python’s parsing should work either way.) After parsing the message, you can easily access individual headers and the body of the message using the same conventions as you used to create messages: headers look like the dictionary key-values of the Message, and the body can be fetched with a function. A simple example of a parser is shown in Listing 12–6. All of the actual parsing takes place in the one-line function message_from_file(); everything else in the program listing is simply an illustration of how a Message object can be mined for headers and data. Listing 12–6. Parsing and Displaying a Simple E-mail #!/usr/bin/env python # Foundations of Python Network Programming - Chapter 12 - trad_parse.py # Traditional Message Parsing # This program requires Python 2.5 or above import email banner = '-' * 48 popular_headers = ('From', 'To', 'Subject', 'Date') msg = email.message_from_file(open('message.txt')) headers = sorted(msg.keys()) print banner 202
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Foundations of Python Network Progr
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To the Python community for creatin
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Contents ■Contents at a Glance ..
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■ CONTENTS Asking getaddrinfo() W
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■ CONTENTS Using Message Queues f
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■ CONTENTS Parsing Dates ........
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■ CONTENTS Telnet ...............
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About the Authors ■ Brandon Craig
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Acknowledgements This book owes its
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■ INTRODUCTION If you do know som
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C H A P T E R 1 ■ ■ ■ Introdu
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CHAPTER 1 ■ INTRODUCTION TO CLIEN
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C H A P T E R 2 ■ ■ ■ UDP The
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CHAPTER 2 ■ UDP server with SSH.
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CHAPTER 2 ■ UDP them anywhere in
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CHAPTER 2 ■ UDP command-line argu
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CHAPTER 2 ■ UDP » » » » raise
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CHAPTER 2 ■ UDP world itself give
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CHAPTER 2 ■ UDP socket that is no
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CHAPTER 2 ■ UDP So binding to an
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CHAPTER 2 ■ UDP s.connect((hostna
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CHAPTER 2 ■ UDP else: » print >>
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C H A P T E R 3 ■ ■ ■ TCP The
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CHAPTER 3 ■ TCP situation), and t
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CHAPTER 3 ■ TCP » reply = recv_a
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CHAPTER 3 ■ TCP guess when the in
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CHAPTER 3 ■ TCP the system has no
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CHAPTER 3 ■ TCP » » » print '\
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CHAPTER 3 ■ TCP $ python tcp_dead
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CHAPTER 3 ■ TCP Using TCP Streams
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CHAPTER 4 ■ SOCKET NAMES AND DNS
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CHAPTER 5 ■ NETWORK DATA AND NETW
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C H A P T E R 6 ■ ■ ■ TLS and
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CHAPTER 6 ■ TLS AND SSL systems a
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CHAPTER 6 ■ TLS AND SSL • He wi
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CHAPTER 6 ■ TLS AND SSL discussio
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CHAPTER 6 ■ TLS AND SSL • The s
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CHAPTER 6 ■ TLS AND SSL The Links
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C H A P T E R 7 ■ ■ ■ Server
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CHAPTER 7 ■ SERVER ARCHITECTURE P
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CHAPTER 7 ■ SERVER ARCHITECTURE
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CHAPTER 7 ■ SERVER ARCHITECTURE N
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CHAPTER 7 ■ SERVER ARCHITECTURE L
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CHAPTER 7 ■ SERVER ARCHITECTURE F
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CHAPTER 7 ■ SERVER ARCHITECTURE p
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CHAPTER 7 ■ SERVER ARCHITECTURE N
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CHAPTER 7 ■ SERVER ARCHITECTURE L
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CHAPTER 7 ■ SERVER ARCHITECTURE s
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CHAPTER 7 ■ SERVER ARCHITECTURE c
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C H A P T E R 8 ■ ■ ■ Caches,
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CHAPTER 8 ■ CACHES, MESSAGE QUEUE
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C H A P T E R 9 ■ ■ ■ HTTP Th
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CHAPTER 9 ■ HTTP Here, the URL sp
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CHAPTER 9 ■ HTTP Relative URLs Ve
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CHAPTER 9 ■ HTTP From now on, I a
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CHAPTER 9 ■ HTTP • 303 See Othe
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CHAPTER 9 ■ HTTP You cannot tell
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CHAPTER 9 ■ HTTP Instead of stuff
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Page 174 and 175: CHAPTER 9 ■ HTTP HTTP Caching Man
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Page 182 and 183: C H A P T E R 10 ■ ■ ■ Screen
Page 184 and 185: CHAPTER 10 ■ SCREEN SCRAPING Figu
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Page 216 and 217: C H A P T E R 12 ■ ■ ■ E-mail
Page 218 and 219: CHAPTER 12 ■ E-MAIL COMPOSITION A
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CHAPTER 15 ■ IMAP key that IMAP h
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CHAPTER 15 ■ IMAP » » print def
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CHAPTER 15 ■ IMAP » From: Brando
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CHAPTER 15 ■ IMAP • \Flagged: T
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CHAPTER 15 ■ IMAP An IMAP message
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CHAPTER 15 ■ IMAP display or summ
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CHAPTER 16 ■ TELNET AND SSH cloud
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CHAPTER 16 ■ TELNET AND SSH Unix
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CHAPTER 16 ■ TELNET AND SSH Do yo
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CHAPTER 16 ■ TELNET AND SSH As we
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CHAPTER 16 ■ TELNET AND SSH tabif
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CHAPTER 16 ■ TELNET AND SSH repla
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CHAPTER 16 ■ TELNET AND SSH Listi
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CHAPTER 16 ■ TELNET AND SSH def p
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CHAPTER 16 ■ TELNET AND SSH We wi
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CHAPTER 16 ■ TELNET AND SSH • p
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CHAPTER 16 ■ TELNET AND SSH You w
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CHAPTER 16 ■ TELNET AND SSH » »
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CHAPTER 16 ■ TELNET AND SSH Listi
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CHAPTER 16 ■ TELNET AND SSH Summa
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CHAPTER 17 ■ FTP The biggest prob
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CHAPTER 17 ■ FTP f.login() print
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CHAPTER 17 ■ FTP if os.path.exist
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CHAPTER 17 ■ FTP f = FTP(host) f.
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CHAPTER 17 ■ FTP Windows servers
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CHAPTER 17 ■ FTP » try: » » f.
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C H A P T E R 18 ■ ■ ■ RPC Re
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CHAPTER 18 ■ RPC sort of proxy ex
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CHAPTER 18 ■ RPC The SimpleXMLRPC
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CHAPTER 18 ■ RPC Traceback (most
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CHAPTER 18 ■ RPC 8.0 If this
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CHAPTER 18 ■ RPC Note that the po
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CHAPTER 18 ■ RPC up being, simply
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CHAPTER 18 ■ RPC such as Python i
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CHAPTER 18 ■ RPC • Google Proto
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■ INDEX mod_python, 194 Qpid, 131
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■ INDEX Common Gateway Interface.
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■ INDEX international characters
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■ INDEX front-end web servers, 17
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■ INDEX deleting folders, 260 del
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■ INDEX mechanize, 138, 163 Memca
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■ INDEX pausing terminal output,
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■ INDEX resources. See also RFCs
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■ INDEX shutdown(), 48 shutting d
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■ INDEX terminals, 270-74 bufferi
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■ INDEX ■ V validating cached r
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