\section{\module{rfc822} ---         Parse RFC 2822 mail headers} \declaremodule{standard}{rfc822}\modulesynopsis{Parse \rfc{2822} style mail messages.} \deprecated{2.3}{The \refmodule{email} package should be used in                 preference to the \module{rfc822} module.  This                 module is present only to maintain backward                 compatibility.} This module defines a class, \class{Message}, which represents an``email message'' as defined by the Internet standard\rfc{2822}.\footnote{This module originally conformed to \rfc{822},hence the name.  Since then, \rfc{2822} has been released as anupdate to \rfc{822}.  This module should be considered\rfc{2822}-conformant, especially in cases where thesyntax or semantics have changed since \rfc{822}.}  Such messagesconsist of a collection of message headers, and a message body.  Thismodule also defines a helper class\class{AddressList} for parsing \rfc{2822} addresses.  Please refer tothe RFC for information on the specific syntax of \rfc{2822} messages. The \refmodule{mailbox}\refstmodindex{mailbox} module provides classes to read mailboxes produced by various end-user mail programs. \begin{classdesc}{Message}{file\optional{, seekable}}A \class{Message} instance is instantiated with an input object asparameter.  Message relies only on the input object having a\method{readline()} method; in particular, ordinary file objectsqualify.  Instantiation reads headers from the input object up to adelimiter line (normally a blank line) and stores them in theinstance.  The message body, following the headers, is not consumed. This class can work with any input object that supports a\method{readline()} method.  If the input object has seek and tellcapability, the \method{rewindbody()} method will work; also, illegallines will be pushed back onto the input stream.  If the input objectlacks seek but has an \method{unread()} method that can push back aline of input, \class{Message} will use that to push back illegallines.  Thus this class can be used to parse messages coming from abuffered stream. The optional \var{seekable} argument is provided as a workaround forcertain stdio libraries in which \cfunction{tell()} discards buffereddata before discovering that the \cfunction{lseek()} system calldoesn't work.  For maximum portability, you should set the seekableargument to zero to prevent that initial \method{tell()} when passingin an unseekable object such as a file object created from a socketobject. Input lines as read from the file may either be terminated by CR-LF orby a single linefeed; a terminating CR-LF is replaced by a singlelinefeed before the line is stored. All header matching is done independent of upper or lower case;e.g.\ \code{\var{m}['From']}, \code{\var{m}['from']} and\code{\var{m}['FROM']} all yield the same result.\end{classdesc} \begin{classdesc}{AddressList}{field}You may instantiate the \class{AddressList} helper class using a singlestring parameter, a comma-separated list of \rfc{2822} addresses to beparsed.  (The parameter \code{None} yields an empty list.)\end{classdesc} \begin{funcdesc}{quote}{str}Return a new string with backslashes in \var{str} replaced by twobackslashes and double quotes replaced by backslash-double quote.\end{funcdesc} \begin{funcdesc}{unquote}{str}Return a new string which is an \emph{unquoted} version of \var{str}.If \var{str} ends and begins with double quotes, they are strippedoff.  Likewise if \var{str} ends and begins with angle brackets, theyare stripped off.\end{funcdesc} \begin{funcdesc}{parseaddr}{address}Parse \var{address}, which should be the value of someaddress-containing field such as \mailheader{To} or \mailheader{Cc},into its constituent ``realname'' and ``email address'' parts.Returns a tuple of that information, unless the parse fails, in whichcase a 2-tuple \code{(None, None)} is returned.\end{funcdesc} \begin{funcdesc}{dump_address_pair}{pair}The inverse of \method{parseaddr()}, this takes a 2-tuple of the form\code{(\var{realname}, \var{email_address})} and returns the stringvalue suitable for a \mailheader{To} or \mailheader{Cc} header.  Ifthe first element of \var{pair} is false, then the second element isreturned unmodified.\end{funcdesc} \begin{funcdesc}{parsedate}{date}Attempts to parse a date according to the rules in \rfc{2822}.however, some mailers don't follow that format as specified, so\function{parsedate()} tries to guess correctly in such cases. \var{date} is a string containing an \rfc{2822} date, such as \code{'Mon, 20 Nov 1995 19:12:08 -0500'}.  If it succeeds in parsingthe date, \function{parsedate()} returns a 9-tuple that can be passeddirectly to \function{time.mktime()}; otherwise \code{None} will bereturned.  Note that fields 6, 7, and 8 of the result tuple are notusable.\end{funcdesc} \begin{funcdesc}{parsedate_tz}{date}Performs the same function as \function{parsedate()}, but returnseither \code{None} or a 10-tuple; the first 9 elements make up a tuplethat can be passed directly to \function{time.mktime()}, and the tenthis the offset of the date's timezone from UTC (which is the officialterm for Greenwich Mean Time).  (Note that the sign of the timezoneoffset is the opposite of the sign of the \code{time.timezone}variable for the same timezone; the latter variable follows the\POSIX{} standard while this module follows \rfc{2822}.)  If the inputstring has no timezone, the last element of the tuple returned is\code{None}.  Note that fields 6, 7, and 8 of the result tuple are notusable.\end{funcdesc} \begin{funcdesc}{mktime_tz}{tuple}Turn a 10-tuple as returned by \function{parsedate_tz()} into a UTCtimestamp.  If the timezone item in the tuple is \code{None}, assumelocal time.  Minor deficiency: this first interprets the first 8elements as a local time and then compensates for the timezonedifference; this may yield a slight error around daylight savings timeswitch dates.  Not enough to worry about for common use.\end{funcdesc}  \begin{seealso}  \seemodule{email}{Comprehensive email handling package; supersedes                    the \module{rfc822} module.}  \seemodule{mailbox}{Classes to read various mailbox formats produced                       by end-user mail programs.}  \seemodule{mimetools}{Subclass of \class{rfc822.Message} that                        handles MIME encoded messages.} \end{seealso}  \subsection{Message Objects \label{message-objects}} A \class{Message} instance has the following methods: \begin{methoddesc}{rewindbody}{}Seek to the start of the message body.  This only works if the fileobject is seekable.\end{methoddesc} \begin{methoddesc}{isheader}{line}Returns a line's canonicalized fieldname (the dictionary key that willbe used to index it) if the line is a legal \rfc{2822} header; otherwisereturns \code{None} (implying that parsing should stop here and theline be pushed back on the input stream).  It is sometimes useful tooverride this method in a subclass.\end{methoddesc} \begin{methoddesc}{islast}{line}Return true if the given line is a delimiter on which Message shouldstop.  The delimiter line is consumed, and the file object's readlocation positioned immediately after it.  By default this method justchecks that the line is blank, but you can override it in a subclass.\end{methoddesc} \begin{methoddesc}{iscomment}{line}Return \code{True} if the given line should be ignored entirely, just skipped.By default this is a stub that always returns \code{False}, but you canoverride it in a subclass.\end{methoddesc} \begin{methoddesc}{getallmatchingheaders}{name}Return a list of lines consisting of all headers matching\var{name}, if any.  Each physical line, whether it is a continuationline or not, is a separate list item.  Return the empty list if noheader matches \var{name}.\end{methoddesc} \begin{methoddesc}{getfirstmatchingheader}{name}Return a list of lines comprising the first header matching\var{name}, and its continuation line(s), if any.  Return\code{None} if there is no header matching \var{name}.\end{methoddesc} \begin{methoddesc}{getrawheader}{name}Return a single string consisting of the text after the colon in thefirst header matching \var{name}.  This includes leading whitespace,the trailing linefeed, and internal linefeeds and whitespace if thereany continuation line(s) were present.  Return \code{None} if there isno header matching \var{name}.\end{methoddesc} \begin{methoddesc}{getheader}{name\optional{, default}}Like \code{getrawheader(\var{name})}, but strip leading and trailingwhitespace.  Internal whitespace is not stripped.  The optional\var{default} argument can be used to specify a different default tobe returned when there is no header matching \var{name}.\end{methoddesc} \begin{methoddesc}{get}{name\optional{, default}}An alias for \method{getheader()}, to make the interface more compatible with regular dictionaries.\end{methoddesc} \begin{methoddesc}{getaddr}{name}Return a pair \code{(\var{full name}, \var{email address})} parsedfrom the string returned by \code{getheader(\var{name})}.  If noheader matching \var{name} exists, return \code{(None, None)};otherwise both the full name and the address are (possibly empty)strings. Example: If \var{m}'s first \mailheader{From} header contains thestring \code{'jack@cwi.nl (Jack Jansen)'}, then\code{m.getaddr('From')} will yield the pair\code{('Jack Jansen', 'jack@cwi.nl')}.If the header contained\code{'Jack Jansen <jack@cwi.nl>'} instead, it would yield theexact same result.\end{methoddesc} \begin{methoddesc}{getaddrlist}{name}This is similar to \code{getaddr(\var{list})}, but parses a headercontaining a list of email addresses (e.g.\ a \mailheader{To} header) andreturns a list of \code{(\var{full name}, \var{email address})} pairs(even if there was only one address in the header).  If there is noheader matching \var{name}, return an empty list. If multiple headers exist that match the named header (e.g. if thereare several \mailheader{Cc} headers), all are parsed for addresses.Any continuation lines the named headers contain are also parsed.\end{methoddesc} \begin{methoddesc}{getdate}{name}Retrieve a header using \method{getheader()} and parse it into a 9-tuplecompatible with \function{time.mktime()}; note that fields 6, 7, and 8 are not usable.  If there is no header matching\var{name}, or it is unparsable, return \code{None}. Date parsing appears to be a black art, and not all mailers adhere tothe standard.  While it has been tested and found correct on a largecollection of email from many sources, it is still possible that thisfunction may occasionally yield an incorrect result.\end{methoddesc} \begin{methoddesc}{getdate_tz}{name}Retrieve a header using \method{getheader()} and parse it into a10-tuple; the first 9 elements will make a tuple compatible with\function{time.mktime()}, and the 10th is a number giving the offsetof the date's timezone from UTC.  Note that fields 6, 7, and 8 are not usable.  Similarly to \method{getdate()}, ifthere is no header matching \var{name}, or it is unparsable, return\code{None}. \end{methoddesc} \class{Message} instances also support a limited mapping interface.In particular: \code{\var{m}[name]} is like\code{\var{m}.getheader(name)} but raises \exception{KeyError} ifthere is no matching header; and \code{len(\var{m})},\code{\var{m}.get(\var{name}\optional{, \var{default}})},\code{\var{m}.has_key(\var{name})}, \code{\var{m}.keys()},\code{\var{m}.values()} \code{\var{m}.items()}, and\code{\var{m}.setdefault(\var{name}\optional{, \var{default}})} act asexpected, with the one difference that \method{setdefault()} usesan empty string as the default value.  \class{Message} instancesalso support the mapping writable interface \code{\var{m}[name] =value} and \code{del \var{m}[name]}.  \class{Message} objects do notsupport the \method{clear()}, \method{copy()}, \method{popitem()}, or\method{update()} methods of the mapping interface.  (Support for\method{get()} and \method{setdefault()} was only added in Python2.2.) Finally, \class{Message} instances have some public instance variables: \begin{memberdesc}{headers}A list containing the entire set of header lines, in the order inwhich they were read (except that setitem calls may disturb thisorder). Each line contains a trailing newline.  Theblank line terminating the headers is not contained in the list.\end{memberdesc} \begin{memberdesc}{fp}The file or file-like object passed at instantiation time.  This canbe used to read the message content.\end{memberdesc} \begin{memberdesc}{unixfrom}The \UNIX{} \samp{From~} line, if the message had one, or an emptystring.  This is needed to regenerate the message in some contexts,such as an \code{mbox}-style mailbox file.\end{memberdesc}  \subsection{AddressList Objects \label{addresslist-objects}} An \class{AddressList} instance has the following methods: \begin{methoddesc}{__len__}{}Return the number of addresses in the address list.\end{methoddesc} \begin{methoddesc}{__str__}{}Return a canonicalized string representation of the address list.Addresses are rendered in "name" <host@domain> form, comma-separated.\end{methoddesc} \begin{methoddesc}{__add__}{alist}Return a new \class{AddressList} instance that contains all addressesin both \class{AddressList} operands, with duplicates removed (setunion).\end{methoddesc} \begin{methoddesc}{__iadd__}{alist}In-place version of \method{__add__()}; turns this \class{AddressList}instance into the union of itself and the right-hand instance,\var{alist}.\end{methoddesc} \begin{methoddesc}{__sub__}{alist}Return a new \class{AddressList} instance that contains every addressin the left-hand \class{AddressList} operand that is not present inthe right-hand address operand (set difference).\end{methoddesc} \begin{methoddesc}{__isub__}{alist}In-place version of \method{__sub__()}, removing addresses in thislist which are also in \var{alist}.\end{methoddesc}  Finally, \class{AddressList} instances have one public instance variable: \begin{memberdesc}{addresslist}A list of tuple string pairs, one per address.  In each member, thefirst is the canonicalized name part, the second is theactual route-address (\character{@}-separated username-host.domainpair).\end{memberdesc}