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

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CHAPTER 15 ■ IMAP key that IMAP has filled in with the information about the message that we asked for: its full text, returned as a large string. Using the email module that we learned about in Chapter 12, the script asks Python to grab the From: line and a bit of the message’s content, and print them to the screen as a summary. Of course, if you wanted to extend this script so that you save the messages in a file or database instead, you can just omit the email parsing step and instead treat the message body as a single string to be deposited in storage and parsed later. Here is what it looks like to run this script: $ ./mailbox_summary.py imap.example.com brandon INBOX Password: 2590 "Amazon.com" Dear Brandon, Portable Power Systems, Inc. shipped the follo ... 2469 Meetup Reminder Parts: text/plain text/html 2470 billing@linode.com Thank you. Please note that charges will appear as "Linode.c ... Of course, if the messages contained large attachments, it could be ruinous to download them in their entirety just to print a summary; but since this is the simplest message-fetching operation, I thought that it would be reasonable to start with it! Downloading Messages Individually E-mail messages can be quite large, and so can mail folders—many mail systems permit users to have hundreds or thousands of messages, that can each be 10MB or more. That kind of mailbox can easily exceed the RAM on the client machine if its contents are all downloaded at once, as in the previous example. To help network-based mail clients that do not want to keep local copies of every message, IMAP supports several operations besides the big “fetch the whole message” command that we saw in the previous section. • An e-mail’s headers can be downloaded as a block of text, separately from the message. • Particular headers from a message can be requested and returned. • The server can be asked to recursively explore and return an outline of the MIME structure of a message. • The text of particular sections of the message can be returned. This allows IMAP clients to perform very efficient queries that download only the information they need to display for the user, decreasing the load on the IMAP server and the network, and allowing results to be displayed more quickly to the user. For an example of how a simple IMAP client works, examine Listing 15–7, which puts together a number of ideas about browsing an IMAP account. Hopefully this provides more context than would be possible if these features were spread out over a half-dozen shorter program listings at this point in the chapter! You can see that the client consists of three concentric loops that each take input from the user as he or she views the list of mail folders, then the list of messages within a particular mail folder, and finally the sections of a specific message. 252
CHAPTER 15 ■ IMAP Listing 15–7. A Simple IMAP Client #!/usr/bin/env python # Foundations of Python Network Programming - Chapter 15 - simple_client.py # Letting a user browse folders, messages, and message parts. import getpass, sys from imapclient import IMAPClient try: » hostname, username = sys.argv[1:] except ValueError: » print 'usage: %s hostname username' % sys.argv[0] » sys.exit(2) banner = '-' * 72 c = IMAPClient(hostname, ssl=True) try: » c.login(username, getpass.getpass()) except c.Error, e: » print 'Could not log in:', e » sys.exit(1) def display_structure(structure, parentparts=[]): » """Attractively display a given message structure.""" » # The whole body of the message is named 'TEXT'. » if parentparts: » » name = '.'.join(parentparts) » else: » » print 'HEADER' » » name = 'TEXT' » # Print this part's designation and its MIME type. » is_multipart = isinstance(structure[0], list) » if is_multipart: » » parttype = 'multipart/%s' % structure[1].lower() » else: » » parttype = ('%s/%s' % structure[:2]).lower() » print '%-9s' % name, parttype, » # For a multipart part, print all of its subordinate parts; for » # other parts, print their disposition (if available). » if is_multipart: » » print » » subparts = structure[0] » » for i in range(len(subparts)): » » » display_structure(subparts[i], parentparts + [ str(i + 1) ]) » else: » » if structure[6]: » » » print 'size=%s' % structure[6], » » if structure[8]: » » » disposition, namevalues = structure[8] » » » print disposition, » » » for i in range(0, len(namevalues), 2): » » » » print '%s=%r' % namevalues[i:i+2] 253
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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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CHAPTER 9 ■ HTTP POST And APIs Al
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CHAPTER 9 ■ HTTP Content Type Neg
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CHAPTER 9 ■ HTTP HTTP Caching Man
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CHAPTER 9 ■ HTTP If the connectio
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CHAPTER 9 ■ HTTP >>> import cooki
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CHAPTER 9 ■ HTTP So the technique
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C H A P T E R 10 ■ ■ ■ Screen
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CHAPTER 10 ■ SCREEN SCRAPING Figu
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CHAPTER 10 ■ SCREEN SCRAPING cont
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CHAPTER 10 ■ SCREEN SCRAPING Thir
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CHAPTER 10 ■ SCREEN SCRAPING Ther
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CHAPTER 10 ■ SCREEN SCRAPING Beau
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CHAPTER 10 ■ SCREEN SCRAPING If y
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CHAPTER 10 ■ SCREEN SCRAPING Cond
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C H A P T E R 11 ■ ■ ■ Web Ap
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CHAPTER 11 ■ WEB APPLICATIONS Thi
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CHAPTER 11 ■ WEB APPLICATIONS But
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CHAPTER 11 ■ WEB APPLICATIONS the
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CHAPTER 11 ■ WEB APPLICATIONS •
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CHAPTER 11 ■ WEB APPLICATIONS hig
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CHAPTER 11 ■ WEB APPLICATIONS The
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CHAPTER 11 ■ WEB APPLICATIONS the
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CHAPTER 11 ■ WEB APPLICATIONS The
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C H A P T E R 12 ■ ■ ■ E-mail
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CHAPTER 12 ■ E-MAIL COMPOSITION A
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Page 238 and 239: CHAPTER 13 ■ SMTP anyway. Outgoin
Page 240 and 241: CHAPTER 13 ■ SMTP How SMTP Is Use
Page 242 and 243: CHAPTER 13 ■ SMTP This mechanism
Page 244 and 245: CHAPTER 13 ■ SMTP s = smtplib.SMT
Page 246 and 247: CHAPTER 13 ■ SMTP ETRN STARTTLS X
Page 248 and 249: CHAPTER 13 ■ SMTP » s = smtplib.
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Page 252 and 253: CHAPTER 13 ■ SMTP username = sys.
Page 254 and 255: C H A P T E R 14 ■ ■ ■ POP PO
Page 256 and 257: CHAPTER 14 ■ POP ■ Caution! Whi
Page 258 and 259: CHAPTER 14 ■ POP finally: » p.qu
Page 260 and 261: CHAPTER 14 ■ POP Subject: Backup
Page 262 and 263: CHAPTER 15 ■ IMAP THE IMAP PROTOC
Page 264 and 265: CHAPTER 15 ■ IMAP '(\\HasNoChildr
Page 266 and 267: CHAPTER 15 ■ IMAP Examining Folde
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Page 278 and 279: CHAPTER 15 ■ IMAP An IMAP message
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Page 282 and 283: CHAPTER 16 ■ TELNET AND SSH cloud
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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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