7.3.1.5 MMDF

7.3.1.5 `MMDF`

class MMDF( path[, factory=None[, create=True]]): A subclass of 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, 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 Mailbox methods implemented by MMDF deserve special remarks:

get_file( key): Using the file after calling flush() or close() on the MMDF instance may yield unpredictable results or raise an exception.

lock( )
unlock( ): Three locking mechanisms are used--dot locking and, if available, the flock() and lockf() system calls.