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

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CHAPTER 15 ■ IMAP An IMAP message has two dates: the internal Date header specified by the sender, which is called its “send date,” and the date at which it actually arrived at the IMAP server. (The former could obviously be a forgery; the latter is as reliable as the IMAP server and its clock.) So there are two sets of criteria for dates, depending on which date you want to query by: BEFORE 01-Jan-1970 ON 01-Jan-1970 SINCE 01-Jan-1970 SENTBEFORE 01-Jan-1970 SENTON 01-Jan-1970 SENTSINCE 01-Jan-1970 Finally, there are two search operations that refer to the text of the message itself—these are the big workhorses that support full-text search of the kind your users are probably expecting when they type into a search field in an e-mail client: BODY string: The message body must contain the string. TEXT string: The entire message, either body or header, must contain the string somewhere. See the documentation for the particular IMAP server you are using to learn whether it returns any “near miss” matches, like those supported by modern search engines, or only exact matches for the words you provide. If your strings contain any characters that IMAP might consider special, try surrounding them with double-quotes, and then backslash-quote any double-quotes within the strings themselves: >>> c.search(r'TEXT "Quoth the raven, \"Nevermore.\""') [2652L] Note that by using an r'...' string here, I avoided having to double up the backslashes to get single backslashes through to IMAP. Manipulating Folders and Messages Creating or deleting folders is done quite simply in IMAP, by providing the name of the folder: c.create_folder('Personal') c.delete_folder('Work') Some IMAP servers or configurations may not permit these operations, or may have restrictions on naming; be sure to have error checking in place when calling them. There are two operations that can create new e-mail messages in your IMAP account besides the “normal” means of waiting for people to send them to you. First, you can copy an existing message from its home folder over into another folder. Start by using select_folder() to visit the folder where the messages live, and then run the copy method like this: c.select_folder('INBOX') c.copy([2653L, 2654L], 'TODO') Finally, it is possible to add a message to a mailbox with IMAP. You do not need to send the message first with SMTP; IMAP is all that is needed. Adding a message is a simple process, though there are a couple of things to be aware of. The primary concern is line endings. Many Unix machines use a single ASCII line feed character (0x0a, or '\n' in Python) to designate the end of a line of text. Windows machines use two characters: CR-LF, a carriage return (0x0D, or '\r' in Python) followed by a line feed. Older Macs use just the carriage return. 260
CHAPTER 15 ■ IMAP Like many Internet protocols (HTTP comes immediately to mind), IMAP internally uses CR-LF ('\r\n' in Python) to designate the end of a line. Some IMAP servers will have problems if you upload a message that uses any other character for the end of a line. Therefore, you must always be careful to have the correct line endings when you translate uploaded messages. This problem is more common than you might expect, since most local mailbox formats use only '\n' for the end of each line. However, you must also be cautious in how carefully you change the line endings, because some messages may use '\r\n' somewhere inside despite using only '\n' for the first few dozen lines, and IMAP clients have been known to fail if a message uses both different line endings! The solution is a simple one, thanks to Python’s powerful splitlines() string method that recognizes all three possible line endings; simply call the function on your message and then re-join the lines with the standard line ending: >>> 'one\rtwo\nthree\r\nfour'.splitlines() ['one', 'two', 'three', 'four'] >>> '\r\n'.join('one\rtwo\nthree\r\nfour'.splitlines()) 'one\r\ntwo\r\nthree\r\nfour' The actual act of appending a message, once you have the line endings correct, is to call the append() method on your IMAP client: c.append('INBOX', my_message) You can also supply a list of flags as a keyword argument, as well as a msg_time to be used as its arrival time by passing a normal Python datetime object. Asynchrony Finally, a major admission needs be made about this chapter’s approach toward IMAP: even though we have described IMAP as though the protocol were synchronous, it in fact supports clients that want to send dozens of requests down the socket to the server and then receive the answers back in whatever order the server can most efficiently fetch the mail from disk and respond. The IMAPClient library hides this protocol flexibility by always sending one request, waiting for the response, and then returning that value. But other libraries—and in particular the IMAP capabilities provided inside Twisted Python—let you take advantage of its asynchronicity. But for most Python programmers needing to script mailbox interactions, the synchronous approach taken in this chapter should work just fine. Summary IMAP is a robust protocol for accessing e-mail messages stored on a remote server. Many IMAP libraries exist for Python; imaplib is built into the Standard Library, but requires you to do all sorts of low-level response parsing by yourself. A far better choice is IMAPClient by Menno Smits, which you can install from the Python Package Index. On an IMAP server, your e-mail messages are grouped into folders, some of which will come predefined by your particular IMAP provider and some of which you can create yourself. An IMAP client can create folders, delete folders, insert new messages into a folder, and move existing messages between folders. Once a folder has been selected, which is the IMAP rough equivalent of a “change directory” command on a filesystem, messages can be listed and fetched very flexibly. Instead of having to download every message in its entirety—though, of course, that is an option—the client can ask for particular information from a message, like a few headers and its message structure, in order to build a 261
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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
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Page 256 and 257: CHAPTER 14 ■ POP ■ Caution! Whi
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Page 262 and 263: CHAPTER 15 ■ IMAP THE IMAP PROTOC
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Page 282 and 283: CHAPTER 16 ■ TELNET AND SSH cloud
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Page 322 and 323: C H A P T E R 18 ■ ■ ■ RPC Re
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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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