:mod:`mailbox` --- Manipulate mailboxes in various formats

.. module:: mailbox :synopsis: Manipulate mailboxes in various formats

.. moduleauthor:: Gregory K. Johnson [email protected] .. sectionauthor:: Gregory K. Johnson [email protected]

Source code: :source:Lib/mailbox.py

This module defines two classes, :class:Mailbox and :class:Message, for accessing and manipulating on-disk mailboxes and the messages they contain. :class:Mailbox offers a dictionary-like mapping from keys to messages. :class:Message extends the :mod:email.message module's :class:~email.message.Message class with format-specific state and behavior. Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.

.. seealso::

Module :mod:email Represent and manipulate messages.

.. _mailbox-objects:

:class:`Mailbox` objects

.. class:: Mailbox

A mailbox, which may be inspected and modified.

The :class:Mailbox class defines an interface and is not intended to be instantiated. Instead, format-specific subclasses should inherit from :class:Mailbox and your code should instantiate a particular subclass.

The :class:Mailbox interface is dictionary-like, with small keys corresponding to messages. Keys are issued by the :class:Mailbox instance with which they will be used and are only meaningful to that :class:Mailbox instance. A key continues to identify a message even if the corresponding message is modified, such as by replacing it with another message.

Messages may be added to a :class:Mailbox instance using the set-like method :meth:add and removed using a del statement or the set-like methods :meth:remove and :meth:discard.

:class:Mailbox interface semantics differ from dictionary semantics in some noteworthy ways. Each time a message is requested, a new representation (typically a :class:Message instance) is generated based upon the current state of the mailbox. Similarly, when a message is added to a :class:Mailbox instance, the provided message representation's contents are copied. In neither case is a reference to the message representation kept by the :class:Mailbox instance.

The default :class:Mailbox iterator iterates over message representations, not keys as the default dictionary iterator does. Moreover, modification of a mailbox during iteration is safe and well-defined. Messages added to the mailbox after an iterator is created will not be seen by the iterator. Messages removed from the mailbox before the iterator yields them will be silently skipped, though using a key from an iterator may result in a :exc:KeyError exception if the corresponding message is subsequently removed.

.. warning::

  Be very cautious when modifying mailboxes that might be simultaneously
  changed by some other process.  The safest mailbox format to use for such
  tasks is Maildir; try to avoid using single-file formats such as mbox for
  concurrent writing.  If you're modifying a mailbox, you *must* lock it by
  calling the :meth:`lock` and :meth:`unlock` methods *before* reading any
  messages in the file or making any changes by adding or deleting a
  message.  Failing to lock the mailbox runs the risk of losing messages or
  corrupting the entire mailbox.

:class:Mailbox instances have the following methods:

.. method:: add(message)

  Add *message* to the mailbox and return the key that has been assigned to
  it.

  Parameter *message* may be a :class:`Message` instance, an
  :class:`email.message.Message` instance, a string, a byte string, or a
  file-like object (which should be open in binary mode). If *message* is
  an instance of the
  appropriate format-specific :class:`Message` subclass (e.g., if it's an
  :class:`mboxMessage` instance and this is an :class:`mbox` instance), its
  format-specific information is used. Otherwise, reasonable defaults for
  format-specific information are used.

  .. versionchanged:: 3.2
     Support for binary input was added.

.. method:: remove(key) delitem(key) discard(key)

  Delete the message corresponding to *key* from the mailbox.

  If no such message exists, a :exc:`KeyError` exception is raised if the
  method was called as :meth:`remove` or :meth:`__delitem__` but no
  exception is raised if the method was called as :meth:`discard`. The
  behavior of :meth:`discard` may be preferred if the underlying mailbox
  format supports concurrent modification by other processes.

.. method:: setitem(key, message)

  Replace the message corresponding to *key* with *message*. Raise a
  :exc:`KeyError` exception if no message already corresponds to *key*.

  As with :meth:`add`, parameter *message* may be a :class:`Message`
  instance, an :class:`email.message.Message` instance, a string, a byte
  string, or a file-like object (which should be open in binary mode). If
  *message* is an
  instance of the appropriate format-specific :class:`Message` subclass
  (e.g., if it's an :class:`mboxMessage` instance and this is an
  :class:`mbox` instance), its format-specific information is
  used. Otherwise, the format-specific information of the message that
  currently corresponds to *key* is left unchanged.

.. method:: iterkeys() keys()

  Return an iterator over all keys if called as :meth:`iterkeys` or return a
  list of keys if called as :meth:`keys`.

.. method:: itervalues() iter() values()

  Return an iterator over representations of all messages if called as
  :meth:`itervalues` or :meth:`__iter__` or return a list of such
  representations if called as :meth:`values`. The messages are represented
  as instances of the appropriate format-specific :class:`Message` subclass
  unless a custom message factory was specified when the :class:`Mailbox`
  instance was initialized.

  .. note::

     The behavior of :meth:`__iter__` is unlike that of dictionaries, which
     iterate over keys.

.. method:: iteritems() items()

  Return an iterator over (*key*, *message*) pairs, where *key* is a key and
  *message* is a message representation, if called as :meth:`iteritems` or
  return a list of such pairs if called as :meth:`items`. The messages are
  represented as instances of the appropriate format-specific
  :class:`Message` subclass unless a custom message factory was specified
  when the :class:`Mailbox` instance was initialized.

.. method:: get(key, default=None) getitem(key)

  Return a representation of the message corresponding to *key*. If no such
  message exists, *default* is returned if the method was called as
  :meth:`get` and a :exc:`KeyError` exception is raised if the method was
  called as :meth:`__getitem__`. The message is represented as an instance
  of the appropriate format-specific :class:`Message` subclass unless a
  custom message factory was specified when the :class:`Mailbox` instance
  was initialized.

.. method:: get_message(key)

  Return a representation of the message corresponding to *key* as an
  instance of the appropriate format-specific :class:`Message` subclass, or
  raise a :exc:`KeyError` exception if no such message exists.

.. method:: get_bytes(key)

  Return a byte representation of the message corresponding to *key*, or
  raise a :exc:`KeyError` exception if no such message exists.

  .. versionadded:: 3.2

.. method:: get_string(key)

  Return a string representation of the message corresponding to *key*, or
  raise a :exc:`KeyError` exception if no such message exists.  The
  message is processed through :class:`email.message.Message` to
  convert it to a 7bit clean representation.

.. method:: get_file(key)

  Return a file-like representation of the message corresponding to *key*,
  or raise a :exc:`KeyError` exception if no such message exists.  The
  file-like object behaves as if open in binary mode.  This file should be
  closed once it is no longer needed.

  .. versionchanged:: 3.2
     The file object really is a binary file; previously it was incorrectly
     returned in text mode.  Also, the file-like object now supports the
     context management protocol: you can use a :keyword:`with` statement to
     automatically close it.

  .. note::

     Unlike other representations of messages, file-like representations are
     not necessarily independent of the :class:`Mailbox` instance that
     created them or of the underlying mailbox.  More specific documentation
     is provided by each subclass.

.. method:: contains(key)

  Return ``True`` if *key* corresponds to a message, ``False`` otherwise.

.. method:: len()

  Return a count of messages in the mailbox.

.. method:: clear()

  Delete all messages from the mailbox.

.. method:: pop(key, default=None)

  Return a representation of the message corresponding to *key* and delete
  the message. If no such message exists, return *default*. The message is
  represented as an instance of the appropriate format-specific
  :class:`Message` subclass unless a custom message factory was specified
  when the :class:`Mailbox` instance was initialized.

.. method:: popitem()

  Return an arbitrary (*key*, *message*) pair, where *key* is a key and
  *message* is a message representation, and delete the corresponding
  message. If the mailbox is empty, raise a :exc:`KeyError` exception. The
  message is represented as an instance of the appropriate format-specific
  :class:`Message` subclass unless a custom message factory was specified
  when the :class:`Mailbox` instance was initialized.

.. method:: update(arg)

  Parameter *arg* should be a *key*-to-*message* mapping or an iterable of
  (*key*, *message*) pairs. Updates the mailbox so that, for each given
  *key* and *message*, the message corresponding to *key* is set to
  *message* as if by using :meth:`__setitem__`. As with :meth:`__setitem__`,
  each *key* must already correspond to a message in the mailbox or else a
  :exc:`KeyError` exception will be raised, so in general it is incorrect
  for *arg* to be a :class:`Mailbox` instance.

  .. note::

     Unlike with dictionaries, keyword arguments are not supported.

.. method:: flush()

  Write any pending changes to the filesystem. For some :class:`Mailbox`
  subclasses, changes are always written immediately and :meth:`flush` does
  nothing, but you should still make a habit of calling this method.

.. method:: lock()

  Acquire an exclusive advisory lock on the mailbox so that other processes
  know not to modify it. An :exc:`ExternalClashError` is raised if the lock
  is not available. The particular locking mechanisms used depend upon the
  mailbox format.  You should *always* lock the mailbox before making any
  modifications to its contents.

.. method:: unlock()

  Release the lock on the mailbox, if any.

.. method:: close()

  Flush the mailbox, unlock it if necessary, and close any open files. For
  some :class:`Mailbox` subclasses, this method does nothing.

.. _mailbox-maildir:

:class:Maildir ^^^^^^^^^^^^^^^^

.. class:: Maildir(dirname, factory=None, create=True)

A subclass of :class:Mailbox for mailboxes in Maildir format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, :class:MaildirMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

It is for historical reasons that dirname is named as such rather than path.

Maildir is a directory-based mailbox format invented for the qmail mail transfer agent and now widely supported by other programs. Messages in a Maildir mailbox are stored in separate files within a common directory structure. This design allows Maildir mailboxes to be accessed and modified by multiple unrelated programs without data corruption, so file locking is unnecessary.

Maildir mailboxes contain three subdirectories, namely: :file:tmp, :file:new, and :file:cur. Messages are created momentarily in the :file:tmp subdirectory and then moved to the :file:new subdirectory to finalize delivery. A mail user agent may subsequently move the message to the :file:cur subdirectory and store information about the state of the message in a special "info" section appended to its file name.

Folders of the style introduced by the Courier mail transfer agent are also supported. Any subdirectory of the main mailbox is considered a folder if '.' is the first character in its name. Folder names are represented by :class:Maildir without the leading '.'. Each folder is itself a Maildir mailbox but should not contain other folders. Instead, a logical nesting is indicated using '.' to delimit levels, e.g., "Archived.2005.07".

.. note::

  The Maildir specification requires the use of a colon (``':'``) in certain
  message file names. However, some operating systems do not permit this
  character in file names, If you wish to use a Maildir-like format on such
  an operating system, you should specify another character to use
  instead. The exclamation point (``'!'``) is a popular choice. For
  example::

     import mailbox
     mailbox.Maildir.colon = '!'

  The :attr:`colon` attribute may also be set on a per-instance basis.

:class:Maildir instances have all of the methods of :class:Mailbox in addition to the following:

.. method:: list_folders()

  Return a list of the names of all folders.

.. method:: get_folder(folder)

  Return a :class:`Maildir` instance representing the folder whose name is
  *folder*. A :exc:`NoSuchMailboxError` exception is raised if the folder
  does not exist.

.. method:: add_folder(folder)

  Create a folder whose name is *folder* and return a :class:`Maildir`
  instance representing it.

.. method:: remove_folder(folder)

  Delete the folder whose name is *folder*. If the folder contains any
  messages, a :exc:`NotEmptyError` exception will be raised and the folder
  will not be deleted.

.. method:: clean()

  Delete temporary files from the mailbox that have not been accessed in the
  last 36 hours. The Maildir specification says that mail-reading programs
  should do this occasionally.

Some :class:Mailbox methods implemented by :class:Maildir deserve special remarks:

.. method:: add(message) setitem(key, message) update(arg)

  .. warning::

     These methods generate unique file names based upon the current process
     ID. When using multiple threads, undetected name clashes may occur and
     cause corruption of the mailbox unless threads are coordinated to avoid
     using these methods to manipulate the same mailbox simultaneously.

.. method:: flush()

  All changes to Maildir mailboxes are immediately applied, so this method
  does nothing.

.. method:: lock() unlock()

  Maildir mailboxes do not support (or require) locking, so these methods do
  nothing.

.. method:: close()

  :class:`Maildir` instances do not keep any open files and the underlying
  mailboxes do not support locking, so this method does nothing.

.. method:: get_file(key)

  Depending upon the host platform, it may not be possible to modify or
  remove the underlying message while the returned file remains open.

.. seealso::

maildir man page from qmail <http://www.qmail.org/man/man5/maildir.html>_ The original specification of the format.

Using maildir format <https://cr.yp.to/proto/maildir.html>_ Notes on Maildir by its inventor. Includes an updated name-creation scheme and details on "info" semantics.

maildir man page from Courier <http://www.courier-mta.org/maildir.html>_ Another specification of the format. Describes a common extension for supporting folders.

.. _mailbox-mbox:

:class:mbox ^^^^^^^^^^^^^

.. class:: mbox(path, factory=None, create=True)

A subclass of :class:Mailbox for mailboxes in mbox format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, :class:mboxMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

The mbox format is the classic format for storing mail on Unix systems. All messages in an mbox mailbox are stored in a single file with the beginning of each message indicated by a line whose first five characters are "From ".

Several variations of the mbox format exist to address perceived shortcomings in the original. In the interest of compatibility, :class:mbox implements the original format, which is sometimes referred to as :dfn:mboxo. This means that the :mailheader:Content-Length header, if present, is ignored and that any occurrences of "From " at the beginning of a line in a message body are transformed to ">From " when storing the message, although occurrences of ">From " are not transformed to "From " when reading the message.

Some :class:Mailbox methods implemented by :class:mbox deserve special remarks:

.. method:: get_file(key)

  Using the file after calling :meth:`flush` or :meth:`close` on the
  :class:`mbox` instance may yield unpredictable results or raise an
  exception.

.. method:: lock() unlock()

  Three locking mechanisms are used---dot locking and, if available, the
  :c:func:`flock` and :c:func:`lockf` system calls.

.. seealso::

mbox man page from qmail <http://www.qmail.org/man/man5/mbox.html>_ A specification of the format and its variations.

mbox man page from tin <http://www.tin.org/bin/man.cgi?section=5&topic=mbox>_ Another specification of the format, with details on locking.

Configuring Netscape Mail on Unix: Why The Content-Length Format is Bad <https://www.jwz.org/doc/content-length.html>_ An argument for using the original mbox format rather than a variation.

"mbox" is a family of several mutually incompatible mailbox formats <https://www.loc.gov/preservation/digital/formats/fdd/fdd000383.shtml>_ A history of mbox variations.

.. _mailbox-mh:

:class:MH ^^^^^^^^^^^

.. class:: MH(path, factory=None, create=True)

A subclass of :class:Mailbox for mailboxes in MH format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, :class:MHMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

MH is a directory-based mailbox format invented for the MH Message Handling System, a mail user agent. Each message in an MH mailbox resides in its own file. An MH mailbox may contain other MH mailboxes (called :dfn:folders) in addition to messages. Folders may be nested indefinitely. MH mailboxes also support :dfn:sequences, which are named lists used to logically group messages without moving them to sub-folders. Sequences are defined in a file called :file:.mh_sequences in each folder.

The :class:MH class manipulates MH mailboxes, but it does not attempt to emulate all of :program:mh's behaviors. In particular, it does not modify and is not affected by the :file:context or :file:.mh_profile files that are used by :program:mh to store its state and configuration.

:class:MH instances have all of the methods of :class:Mailbox in addition to the following:

.. method:: list_folders()

  Return a list of the names of all folders.

.. method:: get_folder(folder)

  Return an :class:`MH` instance representing the folder whose name is
  *folder*. A :exc:`NoSuchMailboxError` exception is raised if the folder
  does not exist.

.. method:: add_folder(folder)

  Create a folder whose name is *folder* and return an :class:`MH` instance
  representing it.

.. method:: remove_folder(folder)

  Delete the folder whose name is *folder*. If the folder contains any
  messages, a :exc:`NotEmptyError` exception will be raised and the folder
  will not be deleted.

.. method:: get_sequences()

  Return a dictionary of sequence names mapped to key lists. If there are no
  sequences, the empty dictionary is returned.

.. method:: set_sequences(sequences)

  Re-define the sequences that exist in the mailbox based upon *sequences*,
  a dictionary of names mapped to key lists, like returned by
  :meth:`get_sequences`.

.. method:: pack()

  Rename messages in the mailbox as necessary to eliminate gaps in
  numbering.  Entries in the sequences list are updated correspondingly.

  .. note::

     Already-issued keys are invalidated by this operation and should not be
     subsequently used.

Some :class:Mailbox methods implemented by :class:MH deserve special remarks:

.. method:: remove(key) delitem(key) discard(key)

  These methods immediately delete the message. The MH convention of marking
  a message for deletion by prepending a comma to its name is not used.

.. method:: lock() unlock()

  Three locking mechanisms are used---dot locking and, if available, the
  :c:func:`flock` and :c:func:`lockf` system calls. For MH mailboxes, locking
  the mailbox means locking the :file:`.mh_sequences` file and, only for the
  duration of any operations that affect them, locking individual message
  files.

.. method:: get_file(key)

  Depending upon the host platform, it may not be possible to remove the
  underlying message while the returned file remains open.

.. method:: flush()

  All changes to MH mailboxes are immediately applied, so this method does
  nothing.

.. method:: close()

  :class:`MH` instances do not keep any open files, so this method is
  equivalent to :meth:`unlock`.

.. seealso::

nmh - Message Handling System <http://www.nongnu.org/nmh/>_ Home page of :program:nmh, an updated version of the original :program:mh.

MH & nmh: Email for Users & Programmers <https://rand-mh.sourceforge.io/book/>_ A GPL-licensed book on :program:mh and :program:nmh, with some information on the mailbox format.

.. _mailbox-babyl:

:class:Babyl ^^^^^^^^^^^^^^

.. class:: Babyl(path, factory=None, create=True)

A subclass of :class:Mailbox for mailboxes in Babyl format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, :class:BabylMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

Babyl is a single-file mailbox format used by the Rmail mail user agent included with Emacs. The beginning of a message is indicated by a line containing the two characters Control-Underscore ('\037') and Control-L ('\014'). The end of a message is indicated by the start of the next message or, in the case of the last message, a line containing a Control-Underscore ('\037') character.

Messages in a Babyl mailbox have two sets of headers, original headers and so-called visible headers. Visible headers are typically a subset of the original headers that have been reformatted or abridged to be more attractive. Each message in a Babyl mailbox also has an accompanying list of :dfn:labels, or short strings that record extra information about the message, and a list of all user-defined labels found in the mailbox is kept in the Babyl options section.

:class:Babyl instances have all of the methods of :class:Mailbox in addition to the following:

.. method:: get_labels()

  Return a list of the names of all user-defined labels used in the mailbox.

  .. note::

     The actual messages are inspected to determine which labels exist in
     the mailbox rather than consulting the list of labels in the Babyl
     options section, but the Babyl section is updated whenever the mailbox
     is modified.

Some :class:Mailbox methods implemented by :class:Babyl deserve special remarks:

.. method:: get_file(key)

  In Babyl mailboxes, the headers of a message are not stored contiguously
  with the body of the message. To generate a file-like representation, the
  headers and body are copied together into an :class:`io.BytesIO` instance,
  which has an API identical to that of a
  file. As a result, the file-like object is truly independent of the
  underlying mailbox but does not save memory compared to a string
  representation.

.. method:: lock() unlock()

  Three locking mechanisms are used---dot locking and, if available, the
  :c:func:`flock` and :c:func:`lockf` system calls.

.. seealso::

Format of Version 5 Babyl Files <https://quimby.gnus.org/notes/BABYL>_ A specification of the Babyl format.

Reading Mail with Rmail <https://www.gnu.org/software/emacs/manual/html_node/emacs/Rmail.html>_ The Rmail manual, with some information on Babyl semantics.

.. _mailbox-mmdf:

:class:MMDF ^^^^^^^^^^^^^

.. class:: MMDF(path, factory=None, create=True)

A subclass of :class:Mailbox for mailboxes in MMDF format. Parameter factory is a callable object that accepts a file-like message representation (which behaves as if opened in binary mode) and returns a custom representation. If factory is None, :class:MMDFMessage is used as the default message representation. If create is True, the mailbox is created if it does not exist.

MMDF is a single-file mailbox format invented for the Multichannel Memorandum Distribution Facility, a mail transfer agent. Each message is in the same form as an mbox message but is bracketed before and after by lines containing four Control-A ('\001') characters. As with the mbox format, the beginning of each message is indicated by a line whose first five characters are "From ", but additional occurrences of "From " are not transformed to ">From " when storing messages because the extra message separator lines prevent mistaking such occurrences for the starts of subsequent messages.

Some :class:Mailbox methods implemented by :class:MMDF deserve special remarks:

.. method:: get_file(key)

  Using the file after calling :meth:`flush` or :meth:`close` on the
  :class:`MMDF` instance may yield unpredictable results or raise an
  exception.

.. method:: lock() unlock()

  Three locking mechanisms are used---dot locking and, if available, the
  :c:func:`flock` and :c:func:`lockf` system calls.

.. seealso::

mmdf man page from tin <http://www.tin.org/bin/man.cgi?section=5&topic=mmdf>_ A specification of MMDF format from the documentation of tin, a newsreader.

MMDF <https://en.wikipedia.org/wiki/MMDF>_ A Wikipedia article describing the Multichannel Memorandum Distribution Facility.

.. _mailbox-message-objects:

:class:`Message` objects

.. class:: Message(message=None)

A subclass of the :mod:email.message module's :class:~email.message.Message. Subclasses of :class:mailbox.Message add mailbox-format-specific state and behavior.

If message is omitted, the new instance is created in a default, empty state. If message is an :class:email.message.Message instance, its contents are copied; furthermore, any format-specific information is converted insofar as possible if message is a :class:Message instance. If message is a string, a byte string, or a file, it should contain an :rfc:2822\ -compliant message, which is read and parsed. Files should be open in binary mode, but text mode files are accepted for backward compatibility.

The format-specific state and behaviors offered by subclasses vary, but in general it is only the properties that are not specific to a particular mailbox that are supported (although presumably the properties are specific to a particular mailbox format). For example, file offsets for single-file mailbox formats and file names for directory-based mailbox formats are not retained, because they are only applicable to the original mailbox. But state such as whether a message has been read by the user or marked as important is retained, because it applies to the message itself.

There is no requirement that :class:Message instances be used to represent messages retrieved using :class:Mailbox instances. In some situations, the time and memory required to generate :class:Message representations might not be acceptable. For such situations, :class:Mailbox instances also offer string and file-like representations, and a custom message factory may be specified when a :class:Mailbox instance is initialized.

.. _mailbox-maildirmessage:

:class:MaildirMessage ^^^^^^^^^^^^^^^^^^^^^^^

.. class:: MaildirMessage(message=None)

A message with Maildir-specific behaviors. Parameter message has the same meaning as with the :class:Message constructor.

Typically, a mail user agent application moves all of the messages in the :file:new subdirectory to the :file:cur subdirectory after the first time the user opens and closes the mailbox, recording that the messages are old whether or not they've actually been read. Each message in :file:cur has an "info" section added to its file name to store information about its state. (Some mail readers may also add an "info" section to messages in :file:new.) The "info" section may take one of two forms: it may contain "2," followed by a list of standardized flags (e.g., "2,FR") or it may contain "1," followed by so-called experimental information. Standard flags for Maildir messages are as follows:

+------+---------+--------------------------------+ | Flag | Meaning | Explanation | +======+=========+================================+ | D | Draft | Under composition | +------+---------+--------------------------------+ | F | Flagged | Marked as important | +------+---------+--------------------------------+ | P | Passed | Forwarded, resent, or bounced | +------+---------+--------------------------------+ | R | Replied | Replied to | +------+---------+--------------------------------+ | S | Seen | Read | +------+---------+--------------------------------+ | T | Trashed | Marked for subsequent deletion | +------+---------+--------------------------------+

:class:MaildirMessage instances offer the following methods:

.. method:: get_subdir()

  Return either "new" (if the message should be stored in the :file:`new`
  subdirectory) or "cur" (if the message should be stored in the :file:`cur`
  subdirectory).

  .. note::

     A message is typically moved from :file:`new` to :file:`cur` after its
     mailbox has been accessed, whether or not the message is has been
     read. A message ``msg`` has been read if ``"S" in msg.get_flags()`` is
     ``True``.

.. method:: set_subdir(subdir)

  Set the subdirectory the message should be stored in. Parameter *subdir*
  must be either "new" or "cur".

.. method:: get_flags()

  Return a string specifying the flags that are currently set. If the
  message complies with the standard Maildir format, the result is the
  concatenation in alphabetical order of zero or one occurrence of each of
  ``'D'``, ``'F'``, ``'P'``, ``'R'``, ``'S'``, and ``'T'``. The empty string
  is returned if no flags are set or if "info" contains experimental
  semantics.

.. method:: set_flags(flags)

  Set the flags specified by *flags* and unset all others.

.. method:: add_flag(flag)

  Set the flag(s) specified by *flag* without changing other flags. To add
  more than one flag at a time, *flag* may be a string of more than one
  character. The current "info" is overwritten whether or not it contains
  experimental information rather than flags.

.. method:: remove_flag(flag)

  Unset the flag(s) specified by *flag* without changing other flags. To
  remove more than one flag at a time, *flag* maybe a string of more than
  one character.  If "info" contains experimental information rather than
  flags, the current "info" is not modified.

.. method:: get_date()

  Return the delivery date of the message as a floating-point number
  representing seconds since the epoch.

.. method:: set_date(date)

  Set the delivery date of the message to *date*, a floating-point number
  representing seconds since the epoch.

.. method:: get_info()

  Return a string containing the "info" for a message. This is useful for
  accessing and modifying "info" that is experimental (i.e., not a list of
  flags).

.. method:: set_info(info)

  Set "info" to *info*, which should be a string.

When a :class:MaildirMessage instance is created based upon an :class:mboxMessage or :class:MMDFMessage instance, the :mailheader:Status and :mailheader:X-Status headers are omitted and the following conversions take place:

When a :class:MaildirMessage instance is created based upon an :class:MHMessage instance, the following conversions take place:

When a :class:MaildirMessage instance is created based upon a :class:BabylMessage instance, the following conversions take place:

.. _mailbox-mboxmessage:

:class:mboxMessage ^^^^^^^^^^^^^^^^^^^^

.. class:: mboxMessage(message=None)

A message with mbox-specific behaviors. Parameter message has the same meaning as with the :class:Message constructor.

Messages in an mbox mailbox are stored together in a single file. The sender's envelope address and the time of delivery are typically stored in a line beginning with "From " that is used to indicate the start of a message, though there is considerable variation in the exact format of this data among mbox implementations. Flags that indicate the state of the message, such as whether it has been read or marked as important, are typically stored in :mailheader:Status and :mailheader:X-Status headers.

Conventional flags for mbox messages are as follows:

+------+----------+--------------------------------+ | Flag | Meaning | Explanation | +======+==========+================================+ | R | Read | Read | +------+----------+--------------------------------+ | O | Old | Previously detected by MUA | +------+----------+--------------------------------+ | D | Deleted | Marked for subsequent deletion | +------+----------+--------------------------------+ | F | Flagged | Marked as important | +------+----------+--------------------------------+ | A | Answered | Replied to | +------+----------+--------------------------------+

The "R" and "O" flags are stored in the :mailheader:Status header, and the "D", "F", and "A" flags are stored in the :mailheader:X-Status header. The flags and headers typically appear in the order mentioned.

:class:mboxMessage instances offer the following methods:

.. method:: get_from()

  Return a string representing the "From " line that marks the start of the
  message in an mbox mailbox. The leading "From " and the trailing newline
  are excluded.

.. method:: set_from(from_, time_=None)

  Set the "From " line to *from_*, which should be specified without a
  leading "From " or trailing newline. For convenience, *time_* may be
  specified and will be formatted appropriately and appended to *from_*. If
  *time_* is specified, it should be a :class:`time.struct_time` instance, a
  tuple suitable for passing to :meth:`time.strftime`, or ``True`` (to use
  :meth:`time.gmtime`).

.. method:: get_flags()

  Return a string specifying the flags that are currently set. If the
  message complies with the conventional format, the result is the
  concatenation in the following order of zero or one occurrence of each of
  ``'R'``, ``'O'``, ``'D'``, ``'F'``, and ``'A'``.

.. method:: set_flags(flags)

  Set the flags specified by *flags* and unset all others. Parameter *flags*
  should be the concatenation in any order of zero or more occurrences of
  each of ``'R'``, ``'O'``, ``'D'``, ``'F'``, and ``'A'``.

.. method:: add_flag(flag)

  Set the flag(s) specified by *flag* without changing other flags. To add
  more than one flag at a time, *flag* may be a string of more than one
  character.

.. method:: remove_flag(flag)

  Unset the flag(s) specified by *flag* without changing other flags. To
  remove more than one flag at a time, *flag* maybe a string of more than
  one character.

When an :class:mboxMessage instance is created based upon a :class:MaildirMessage instance, a "From " line is generated based upon the :class:MaildirMessage instance's delivery date, and the following conversions take place:

When an :class:mboxMessage instance is created based upon an :class:MHMessage instance, the following conversions take place:

When an :class:mboxMessage instance is created based upon a :class:BabylMessage instance, the following conversions take place:

When a :class:Message instance is created based upon an :class:MMDFMessage instance, the "From " line is copied and all flags directly correspond:

.. _mailbox-mhmessage:

:class:MHMessage ^^^^^^^^^^^^^^^^^^

.. class:: MHMessage(message=None)

A message with MH-specific behaviors. Parameter message has the same meaning as with the :class:Message constructor.

MH messages do not support marks or flags in the traditional sense, but they do support sequences, which are logical groupings of arbitrary messages. Some mail reading programs (although not the standard :program:mh and :program:nmh) use sequences in much the same way flags are used with other formats, as follows:

:class:MHMessage instances offer the following methods:

.. method:: get_sequences()

  Return a list of the names of sequences that include this message.

.. method:: set_sequences(sequences)

  Set the list of sequences that include this message.

.. method:: add_sequence(sequence)

  Add *sequence* to the list of sequences that include this message.

.. method:: remove_sequence(sequence)

  Remove *sequence* from the list of sequences that include this message.

When an :class:MHMessage instance is created based upon a :class:MaildirMessage instance, the following conversions take place:

When an :class:MHMessage instance is created based upon an :class:mboxMessage or :class:MMDFMessage instance, the :mailheader:Status and :mailheader:X-Status headers are omitted and the following conversions take place:

When an :class:MHMessage instance is created based upon a :class:BabylMessage instance, the following conversions take place:

.. _mailbox-babylmessage:

:class:BabylMessage ^^^^^^^^^^^^^^^^^^^^^

.. class:: BabylMessage(message=None)

A message with Babyl-specific behaviors. Parameter message has the same meaning as with the :class:Message constructor.

Certain message labels, called :dfn:attributes, are defined by convention to have special meanings. The attributes are as follows:

By default, Rmail displays only visible headers. The :class:BabylMessage class, though, uses the original headers because they are more complete. Visible headers may be accessed explicitly if desired.

:class:BabylMessage instances offer the following methods:

.. method:: get_labels()

  Return a list of labels on the message.

.. method:: set_labels(labels)

  Set the list of labels on the message to *labels*.

.. method:: add_label(label)

  Add *label* to the list of labels on the message.

.. method:: remove_label(label)

  Remove *label* from the list of labels on the message.

.. method:: get_visible()

  Return an :class:`Message` instance whose headers are the message's
  visible headers and whose body is empty.

.. method:: set_visible(visible)

  Set the message's visible headers to be the same as the headers in
  *message*.  Parameter *visible* should be a :class:`Message` instance, an
  :class:`email.message.Message` instance, a string, or a file-like object
  (which should be open in text mode).

.. method:: update_visible()

  When a :class:`BabylMessage` instance's original headers are modified, the
  visible headers are not automatically modified to correspond. This method
  updates the visible headers as follows: each visible header with a
  corresponding original header is set to the value of the original header,
  each visible header without a corresponding original header is removed,
  and any of :mailheader:`Date`, :mailheader:`From`, :mailheader:`Reply-To`,
  :mailheader:`To`, :mailheader:`CC`, and :mailheader:`Subject` that are
  present in the original headers but not the visible headers are added to
  the visible headers.

When a :class:BabylMessage instance is created based upon a :class:MaildirMessage instance, the following conversions take place:

When a :class:BabylMessage instance is created based upon an :class:mboxMessage or :class:MMDFMessage instance, the :mailheader:Status and :mailheader:X-Status headers are omitted and the following conversions take place:

When a :class:BabylMessage instance is created based upon an :class:MHMessage instance, the following conversions take place:

.. _mailbox-mmdfmessage:

:class:MMDFMessage ^^^^^^^^^^^^^^^^^^^^

.. class:: MMDFMessage(message=None)

A message with MMDF-specific behaviors. Parameter message has the same meaning as with the :class:Message constructor.

As with message in an mbox mailbox, MMDF messages are stored with the sender's address and the delivery date in an initial line beginning with "From ". Likewise, flags that indicate the state of the message are typically stored in :mailheader:Status and :mailheader:X-Status headers.

Conventional flags for MMDF messages are identical to those of mbox message and are as follows:

:class:MMDFMessage instances offer the following methods, which are identical to those offered by :class:mboxMessage:

.. method:: get_from()

  Return a string representing the "From " line that marks the start of the
  message in an mbox mailbox. The leading "From " and the trailing newline
  are excluded.

.. method:: set_from(from_, time_=None)

  Set the "From " line to *from_*, which should be specified without a
  leading "From " or trailing newline. For convenience, *time_* may be
  specified and will be formatted appropriately and appended to *from_*. If
  *time_* is specified, it should be a :class:`time.struct_time` instance, a
  tuple suitable for passing to :meth:`time.strftime`, or ``True`` (to use
  :meth:`time.gmtime`).

.. method:: get_flags()

  Return a string specifying the flags that are currently set. If the
  message complies with the conventional format, the result is the
  concatenation in the following order of zero or one occurrence of each of
  ``'R'``, ``'O'``, ``'D'``, ``'F'``, and ``'A'``.

.. method:: set_flags(flags)

  Set the flags specified by *flags* and unset all others. Parameter *flags*
  should be the concatenation in any order of zero or more occurrences of
  each of ``'R'``, ``'O'``, ``'D'``, ``'F'``, and ``'A'``.

.. method:: add_flag(flag)

  Set the flag(s) specified by *flag* without changing other flags. To add
  more than one flag at a time, *flag* may be a string of more than one
  character.

.. method:: remove_flag(flag)

  Unset the flag(s) specified by *flag* without changing other flags. To
  remove more than one flag at a time, *flag* maybe a string of more than
  one character.

When an :class:MMDFMessage instance is created based upon a :class:MaildirMessage instance, a "From " line is generated based upon the :class:MaildirMessage instance's delivery date, and the following conversions take place:

When an :class:MMDFMessage instance is created based upon an :class:MHMessage instance, the following conversions take place:

When an :class:MMDFMessage instance is created based upon a :class:BabylMessage instance, the following conversions take place:

When an :class:MMDFMessage instance is created based upon an :class:mboxMessage instance, the "From " line is copied and all flags directly correspond:

Exceptions

The following exception classes are defined in the :mod:mailbox module:

.. exception:: Error()

The based class for all other module-specific exceptions.

.. exception:: NoSuchMailboxError()

Raised when a mailbox is expected but is not found, such as when instantiating a :class:Mailbox subclass with a path that does not exist (and with the create parameter set to False), or when opening a folder that does not exist.

.. exception:: NotEmptyError()

Raised when a mailbox is not empty but is expected to be, such as when deleting a folder that contains messages.

.. exception:: ExternalClashError()

Raised when some mailbox-related condition beyond the control of the program causes it to be unable to proceed, such as when failing to acquire a lock that another program already holds a lock, or when a uniquely-generated file name already exists.

.. exception:: FormatError()

Raised when the data in a file cannot be parsed, such as when an :class:MH instance attempts to read a corrupted :file:.mh_sequences file.

.. _mailbox-examples:

Examples

A simple example of printing the subjects of all messages in a mailbox that seem interesting::

import mailbox for message in mailbox.mbox('~/mbox'): subject = message['subject'] # Could possibly be None. if subject and 'python' in subject.lower(): print(subject)

To copy all mail from a Babyl mailbox to an MH mailbox, converting all of the format-specific information that can be converted::

import mailbox destination = mailbox.MH('~~/Mail') destination.lock() for message in mailbox.Babyl('~~/RMAIL'): destination.add(mailbox.MHMessage(message)) destination.flush() destination.unlock()

This example sorts mail from several mailing lists into different mailboxes, being careful to avoid mail corruption due to concurrent modification by other programs, mail loss due to interruption of the program, or premature termination due to malformed messages in the mailbox::

import mailbox import email.errors

list_names = ('python-list', 'python-dev', 'python-bugs')

boxes = {name: mailbox.mbox('~~/email/%s' % name) for name in list_names} inbox = mailbox.Maildir('~~/Maildir', factory=None)

for key in inbox.iterkeys(): try: message = inbox[key] except email.errors.MessageParseError: continue # The message is malformed. Just leave it.

   for name in list_names:
       list_id = message['list-id']
       if list_id and name in list_id:
           # Get mailbox to use
           box = boxes[name]

           # Write copy to disk before removing original.
           # If there's a crash, you might duplicate a message, but
           # that's better than losing a message completely.
           box.lock()
           box.add(message)
           box.flush()
           box.unlock()

           # Remove original message
           inbox.lock()
           inbox.discard(key)
           inbox.flush()
           inbox.unlock()
           break               # Found destination, so stop looking.

for box in boxes.itervalues(): box.close()

:mod:`mailbox` --- Manipulate mailboxes in various formats

:mod:mailbox --- Manipulate mailboxes in various formats

:class:Mailbox objects

:class:Message objects

Exceptions

Examples

:mod:`mailbox` --- Manipulate mailboxes in various formats

:class:`Mailbox` objects

:class:`Message` objects