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# 20.10. `imaplib` — IMAP4 protocol client

Source code: Lib/imaplib.py

This module defines three classes, `IMAP4`, `IMAP4_SSL` and `IMAP4_stream`, which encapsulate a connection to an IMAP4 server and implement a large subset of the IMAP4rev1 client protocol as defined in RFC 2060. It is backward compatible with IMAP4 (RFC 1730) servers, but note that the `STATUS` command is not supported in IMAP4.

Three classes are provided by the `imaplib` module, `IMAP4` is the base class:

class `imaplib.``IMAP4`([host[, port]])

  This class implements the actual IMAP4 protocol. The connection is created and protocol version (IMAP4 or IMAP4rev1) is determined when the instance is initialized. If host is not specified, `''` (the local host) is used. If port is omitted, the standard IMAP4 port (143) is used.

Three exceptions are defined as attributes of the `IMAP4` class:

exception `IMAP4.``error`

  Exception raised on any errors. The reason for the exception is passed to the constructor as a string.

exception `IMAP4.``abort`

  IMAP4 server errors cause this exception to be raised. This is a sub-class of `IMAP4.error`. Note that closing the instance and instantiating a new one will usually allow recovery from this exception.

exception `IMAP4.``readonly`

  This exception is raised when a writable mailbox has its status changed by the server. This is a sub-class of `IMAP4.error`. Some other client now has write permission, and the mailbox will need to be re-opened to re-obtain write permission.

There’s also a subclass for secure connections:

class `imaplib.``IMAP4_SSL`([host[, port[, keyfile[, certfile]]]])

  This is a subclass derived from `IMAP4` that connects over an SSL encrypted socket (to use this class you need a socket module that was compiled with SSL support). If host is not specified, `''` (the local host) is used. If port is omitted, the standard IMAP4-over-SSL port (993) is used. keyfile and certfile are also optional - they can contain a PEM formatted private key and certificate chain file for the SSL connection.

The second subclass allows for connections created by a child process:

class `imaplib.``IMAP4_stream`(command)

  This is a subclass derived from `IMAP4` that connects to the `stdin/stdout` file descriptors created by passing command to `os.popen2()`.

  2.3 新版功能.

The following utility functions are defined:

`imaplib.``Internaldate2tuple`(datestr)

  Parse an IMAP4 `INTERNALDATE` string and return corresponding local time. The return value is a `time.struct_time` instance or `None` if the string has wrong format.

`imaplib.``Int2AP`(num)

  Converts an integer into a string representation using characters from the set [`A` .. `P`].

`imaplib.``ParseFlags`(flagstr)

  Converts an IMAP4 `FLAGS` response to a tuple of individual flags.

`imaplib.``Time2Internaldate`(date_time)

  Convert date_time to an IMAP4 `INTERNALDATE` representation. The return value is a string in the form: `"DD-Mmm-YYYY HH:MM:SS +HHMM"` (including double-quotes). The date_time argument can be a number (int or float) representing seconds since epoch (as returned by `time.time()`), a 9-tuple representing local time (as returned by `time.localtime()`), or a double-quoted string. In the last case, it is assumed to already be in the correct format.

Note that IMAP4 message numbers change as the mailbox changes; in particular, after an `EXPUNGE` command performs deletions the remaining messages are renumbered. So it is highly advisable to use UIDs instead, with the UID command.

At the end of the module, there is a test section that contains a more extensive example of usage.

参见

Documents describing the protocol, and sources and binaries for servers implementing it, can all be found at the University of Washington’s IMAP Information Center (https://www.washington.edu/imap/).

## 20.10.1. IMAP4 Objects

All IMAP4rev1 commands are represented by methods of the same name, either upper-case or lower-case.

All arguments to commands are converted to strings, except for `AUTHENTICATE`, and the last argument to `APPEND` which is passed as an IMAP4 literal. If necessary (the string contains IMAP4 protocol-sensitive characters and isn’t enclosed with either parentheses or double quotes) each string is quoted. However, the password argument to the `LOGIN` command is always quoted. If you want to avoid having an argument string quoted (eg: the flags argument to `STORE`) then enclose the string in parentheses (eg: `r'(\Deleted)'`).

Each command returns a tuple: `(type, [data, ...])` where type is usually `'OK'` or `'NO'`, and data is either the text from the command response, or mandated results from the command. Each data is either a string, or a tuple. If a tuple, then the first part is the header of the response, and the second part contains the data (ie: ‘literal’ value).

The message_set options to commands below is a string specifying one or more messages to be acted upon. It may be a simple message number (`'1'`), a range of message numbers (`'2:4'`), or a group of non-contiguous ranges separated by commas (`'1:3,6:9'`). A range can contain an asterisk to indicate an infinite upper bound (`'3:*'`).

An `IMAP4` instance has the following methods:

`IMAP4.``append`(mailbox, flags, date_time, message)

  Append message to named mailbox.

`IMAP4.``authenticate`(mechanism, authobject)

  Authenticate command — requires response processing.

  mechanism specifies which authentication mechanism is to be used - it should appear in the instance variable `capabilities` in the form `AUTH=mechanism`.

  authobject must be a callable object:

      data = authobject(response)

  It will be called to process server continuation responses. It should return `data` that will be encoded and sent to server. It should return `None` if the client abort response `*` should be sent instead.

`IMAP4.``check`()

  Checkpoint mailbox on server.

`IMAP4.``close`()

  Close currently selected mailbox. Deleted messages are removed from writable mailbox. This is the recommended command before `LOGOUT`.

`IMAP4.``copy`(message_set, new_mailbox)

  Copy message_set messages onto end of new_mailbox.

`IMAP4.``create`(mailbox)

  Create new mailbox named mailbox.

`IMAP4.``delete`(mailbox)

  Delete old mailbox named mailbox.

`IMAP4.``deleteacl`(mailbox, who)

  Delete the ACLs (remove any rights) set for who on mailbox.

  2.4 新版功能.

`IMAP4.``expunge`()

  Permanently remove deleted items from selected mailbox. Generates an `EXPUNGE` response for each deleted message. Returned data contains a list of `EXPUNGE` message numbers in order received.

`IMAP4.``fetch`(message_set, message_parts)

  Fetch (parts of) messages. message_parts should be a string of message part names enclosed within parentheses, eg: `"(UID BODY[TEXT])"`. Returned data are tuples of message part envelope and data.

`IMAP4.``getacl`(mailbox)

  Get the `ACL`s for mailbox. The method is non-standard, but is supported by the `Cyrus` server.

`IMAP4.``getannotation`(mailbox, entry, attribute)

  Retrieve the specified `ANNOTATION`s for mailbox. The method is non-standard, but is supported by the `Cyrus` server.

  2.5 新版功能.

`IMAP4.``getquota`(root)

  Get the `quota` root’s resource usage and limits. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

  2.3 新版功能.

`IMAP4.``getquotaroot`(mailbox)

  Get the list of `quota` `roots` for the named mailbox. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

  2.3 新版功能.

`IMAP4.``list`([directory[, pattern]])

  List mailbox names in directory matching pattern. directory defaults to the top-level mail folder, and pattern defaults to match anything. Returned data contains a list of `LIST` responses.

`IMAP4.``login`(user, password)

  Identify the client using a plaintext password. The password will be quoted.

`IMAP4.``login_cram_md5`(user, password)

  Force use of `CRAM-MD5` authentication when identifying the client to protect the password. Will only work if the server `CAPABILITY` response includes the phrase `AUTH=CRAM-MD5`.

  2.3 新版功能.

`IMAP4.``logout`()

  Shutdown connection to server. Returns server `BYE` response.

`IMAP4.``lsub`([directory[, pattern]])

  List subscribed mailbox names in directory matching pattern. directory defaults to the top level directory and pattern defaults to match any mailbox. Returned data are tuples of message part envelope and data.

`IMAP4.``myrights`(mailbox)

  Show my ACLs for a mailbox (i.e. the rights that I have on mailbox).

  2.4 新版功能.

`IMAP4.``namespace`()

  Returns IMAP namespaces as defined in RFC2342.

  2.3 新版功能.

`IMAP4.``noop`()

  Send `NOOP` to server.

`IMAP4.``open`(host, port)

  Opens socket to port at host. This method is implicitly called by the `IMAP4` constructor. The connection objects established by this method will be used in the `IMAP4.read()`, `IMAP4.readline()`, `IMAP4.send()`, and `IMAP4.shutdown()` methods. You may override this method.

`IMAP4.``partial`(message_num, message_part, start, length)

  Fetch truncated part of a message. Returned data is a tuple of message part envelope and data.

`IMAP4.``proxyauth`(user)

  Assume authentication as user. Allows an authorised administrator to proxy into any user’s mailbox.

  2.3 新版功能.

`IMAP4.``read`(size)

  Reads size bytes from the remote server. You may override this method.

`IMAP4.``readline`()

  Reads one line from the remote server. You may override this method.

`IMAP4.``recent`()

  Prompt server for an update. Returned data is `None` if no new messages, else value of `RECENT` response.

`IMAP4.``rename`(oldmailbox, newmailbox)

  Rename mailbox named oldmailbox to newmailbox.

`IMAP4.``response`(code)

  Return data for response code if received, or `None`. Returns the given code, instead of the usual type.

`IMAP4.``search`(charset, criterion[, ...])

  Search mailbox for matching messages. charset may be `None`, in which case no `CHARSET` will be specified in the request to the server. The IMAP protocol requires that at least one criterion be specified; an exception will be raised when the server returns an error.

  示例:

      # M is a connected IMAP4 instance...
      typ, msgnums = M.search(None, 'FROM', '"LDJ"')

      # or:
      typ, msgnums = M.search(None, '(FROM "LDJ")')

`IMAP4.``select`([mailbox[, readonly]])

  Select a mailbox. Returned data is the count of messages in mailbox (`EXISTS` response). The default mailbox is `'INBOX'`. If the readonly flag is set, modifications to the mailbox are not allowed.

`IMAP4.``send`(data)

  Sends `data` to the remote server. You may override this method.

`IMAP4.``setacl`(mailbox, who, what)

  Set an `ACL` for mailbox. The method is non-standard, but is supported by the `Cyrus` server.

`IMAP4.``setannotation`(mailbox, entry, attribute[, ...])

  Set `ANNOTATION`s for mailbox. The method is non-standard, but is supported by the `Cyrus` server.

  2.5 新版功能.

`IMAP4.``setquota`(root, limits)

  Set the `quota` root’s resource limits. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

  2.3 新版功能.

`IMAP4.``shutdown`()

  Close connection established in `open`. This method is implicitly called by `IMAP4.logout()`. You may override this method.

`IMAP4.``socket`()

  Returns socket instance used to connect to server.

`IMAP4.``sort`(sort_criteria, charset, search_criterion[, ...])

  The `sort` command is a variant of `search` with sorting semantics for the results. Returned data contains a space separated list of matching message numbers.

  Sort has two arguments before the search_criterion argument(s); a parenthesized list of sort_criteria, and the searching charset. Note that unlike `search`, the searching charset argument is mandatory. There is also a `uid sort` command which corresponds to `sort` the way that `uid search` corresponds to `search`. The `sort` command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria. It then returns the numbers of matching messages.

  This is an `IMAP4rev1` extension command.

`IMAP4.``status`(mailbox, names)

  Request named status conditions for mailbox.

`IMAP4.``store`(message_set, command, flag_list)

  Alters flag dispositions for messages in mailbox. command is specified by section 6.4.6 of RFC 2060 as being one of “FLAGS”, “+FLAGS”, or “-FLAGS”, optionally with a suffix of “.SILENT”.

  For example, to set the delete flag on all messages:

      typ, data = M.search(None, 'ALL')
      for num in data[0].split():
         M.store(num, '+FLAGS', '\\Deleted')
      M.expunge()

`IMAP4.``subscribe`(mailbox)

  Subscribe to new mailbox.

`IMAP4.``thread`(threading_algorithm, charset, search_criterion[, ...])

  The `thread` command is a variant of `search` with threading semantics for the results. Returned data contains a space separated list of thread members.

  Thread members consist of zero or more messages numbers, delimited by spaces, indicating successive parent and child.

  Thread has two arguments before the search_criterion argument(s); a threading_algorithm, and the searching charset. Note that unlike `search`, the searching charset argument is mandatory. There is also a `uid thread` command which corresponds to `thread` the way that `uid search` corresponds to `search`. The `thread` command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria. It then returns the matching messages threaded according to the specified threading algorithm.

  This is an `IMAP4rev1` extension command.

  2.4 新版功能.

`IMAP4.``uid`(command, arg[, ...])

  Execute command args with messages identified by UID, rather than message number. Returns response appropriate to command. At least one argument must be supplied; if none are provided, the server will return an error and an exception will be raised.

`IMAP4.``unsubscribe`(mailbox)

  Unsubscribe from old mailbox.

`IMAP4.``xatom`(name[, arg[, ...]])

  Allow simple extension commands notified by server in `CAPABILITY` response.

Instances of `IMAP4_SSL` have just one additional method:

`IMAP4_SSL.``ssl`()

  Returns SSLObject instance used for the secure connection with the server.

The following attributes are defined on instances of `IMAP4`:

`IMAP4.``PROTOCOL_VERSION`

  The most recent supported protocol in the `CAPABILITY` response from the server.

`IMAP4.``debug`

  Integer value to control debugging output. The initialize value is taken from the module variable `Debug`. Values greater than three trace each command.

## 20.10.2. IMAP4 Example

Here is a minimal example (without error checking) that opens a mailbox and retrieves and prints all messages:

    import getpass, imaplib

    M = imaplib.IMAP4()
    M.login(getpass.getuser(), getpass.getpass())
    M.select()
    typ, data = M.search(None, 'ALL')
    for num in data[0].split():
        typ, data = M.fetch(num, '(RFC822)')
        print 'Message %s\n%s\n' % (num, data[0][1])
    M.close()
    M.logout()