337 lines
14 KiB
TeX
337 lines
14 KiB
TeX
\section{\module{rfc822} ---
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Parse RFC 2822 mail headers}
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\declaremodule{standard}{rfc822}
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\modulesynopsis{Parse \rfc{2822} style mail messages.}
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\deprecated{2.3}{The \refmodule{email} package should be used in
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preference to the \module{rfc822} module. This
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module is present only to maintain backward
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compatibility.}
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This module defines a class, \class{Message}, which represents an
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``email message'' as defined by the Internet standard
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\rfc{2822}.\footnote{This module originally conformed to \rfc{822},
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hence the name. Since then, \rfc{2822} has been released as an
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update to \rfc{822}. This module should be considered
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\rfc{2822}-conformant, especially in cases where the
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syntax or semantics have changed since \rfc{822}.} Such messages
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consist of a collection of message headers, and a message body. This
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module also defines a helper class
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\class{AddressList} for parsing \rfc{2822} addresses. Please refer to
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the RFC for information on the specific syntax of \rfc{2822} messages.
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The \refmodule{mailbox}\refstmodindex{mailbox} module provides classes
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to read mailboxes produced by various end-user mail programs.
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\begin{classdesc}{Message}{file\optional{, seekable}}
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A \class{Message} instance is instantiated with an input object as
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parameter. Message relies only on the input object having a
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\method{readline()} method; in particular, ordinary file objects
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qualify. Instantiation reads headers from the input object up to a
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delimiter line (normally a blank line) and stores them in the
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instance. The message body, following the headers, is not consumed.
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This class can work with any input object that supports a
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\method{readline()} method. If the input object has seek and tell
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capability, the \method{rewindbody()} method will work; also, illegal
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lines will be pushed back onto the input stream. If the input object
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lacks seek but has an \method{unread()} method that can push back a
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line of input, \class{Message} will use that to push back illegal
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lines. Thus this class can be used to parse messages coming from a
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buffered stream.
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The optional \var{seekable} argument is provided as a workaround for
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certain stdio libraries in which \cfunction{tell()} discards buffered
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data before discovering that the \cfunction{lseek()} system call
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doesn't work. For maximum portability, you should set the seekable
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argument to zero to prevent that initial \method{tell()} when passing
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in an unseekable object such as a a file object created from a socket
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object.
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Input lines as read from the file may either be terminated by CR-LF or
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by a single linefeed; a terminating CR-LF is replaced by a single
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linefeed before the line is stored.
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All header matching is done independent of upper or lower case;
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e.g.\ \code{\var{m}['From']}, \code{\var{m}['from']} and
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\code{\var{m}['FROM']} all yield the same result.
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\end{classdesc}
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\begin{classdesc}{AddressList}{field}
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You may instantiate the \class{AddressList} helper class using a single
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string parameter, a comma-separated list of \rfc{2822} addresses to be
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parsed. (The parameter \code{None} yields an empty list.)
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\end{classdesc}
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\begin{funcdesc}{quote}{str}
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Return a new string with backslashes in \var{str} replaced by two
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backslashes and double quotes replaced by backslash-double quote.
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\end{funcdesc}
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\begin{funcdesc}{unquote}{str}
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Return a new string which is an \emph{unquoted} version of \var{str}.
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If \var{str} ends and begins with double quotes, they are stripped
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off. Likewise if \var{str} ends and begins with angle brackets, they
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are stripped off.
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\end{funcdesc}
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\begin{funcdesc}{parseaddr}{address}
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Parse \var{address}, which should be the value of some
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address-containing field such as \mailheader{To} or \mailheader{Cc},
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into its constituent ``realname'' and ``email address'' parts.
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Returns a tuple of that information, unless the parse fails, in which
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case a 2-tuple \code{(None, None)} is returned.
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\end{funcdesc}
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\begin{funcdesc}{dump_address_pair}{pair}
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The inverse of \method{parseaddr()}, this takes a 2-tuple of the form
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\code{(\var{realname}, \var{email_address})} and returns the string
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value suitable for a \mailheader{To} or \mailheader{Cc} header. If
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the first element of \var{pair} is false, then the second element is
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returned unmodified.
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\end{funcdesc}
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\begin{funcdesc}{parsedate}{date}
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Attempts to parse a date according to the rules in \rfc{2822}.
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however, some mailers don't follow that format as specified, so
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\function{parsedate()} tries to guess correctly in such cases.
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\var{date} is a string containing an \rfc{2822} date, such as
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\code{'Mon, 20 Nov 1995 19:12:08 -0500'}. If it succeeds in parsing
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the date, \function{parsedate()} returns a 9-tuple that can be passed
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directly to \function{time.mktime()}; otherwise \code{None} will be
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returned. Note that fields 6, 7, and 8 of the result tuple are not
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usable.
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\end{funcdesc}
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\begin{funcdesc}{parsedate_tz}{date}
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Performs the same function as \function{parsedate()}, but returns
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either \code{None} or a 10-tuple; the first 9 elements make up a tuple
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that can be passed directly to \function{time.mktime()}, and the tenth
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is the offset of the date's timezone from UTC (which is the official
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term for Greenwich Mean Time). (Note that the sign of the timezone
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offset is the opposite of the sign of the \code{time.timezone}
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variable for the same timezone; the latter variable follows the
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\POSIX{} standard while this module follows \rfc{2822}.) If the input
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string has no timezone, the last element of the tuple returned is
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\code{None}. Note that fields 6, 7, and 8 of the result tuple are not
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usable.
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\end{funcdesc}
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\begin{funcdesc}{mktime_tz}{tuple}
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Turn a 10-tuple as returned by \function{parsedate_tz()} into a UTC
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timestamp. If the timezone item in the tuple is \code{None}, assume
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local time. Minor deficiency: this first interprets the first 8
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elements as a local time and then compensates for the timezone
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difference; this may yield a slight error around daylight savings time
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switch dates. Not enough to worry about for common use.
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\end{funcdesc}
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\begin{seealso}
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\seemodule{email}{Comprehensive email handling package; supercedes
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the \module{rfc822} module.}
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\seemodule{mailbox}{Classes to read various mailbox formats produced
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by end-user mail programs.}
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\seemodule{mimetools}{Subclass of \class{rfc822.Message} that
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handles MIME encoded messages.}
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\end{seealso}
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\subsection{Message Objects \label{message-objects}}
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A \class{Message} instance has the following methods:
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\begin{methoddesc}{rewindbody}{}
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Seek to the start of the message body. This only works if the file
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object is seekable.
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\end{methoddesc}
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\begin{methoddesc}{isheader}{line}
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Returns a line's canonicalized fieldname (the dictionary key that will
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be used to index it) if the line is a legal \rfc{2822} header; otherwise
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returns \code{None} (implying that parsing should stop here and the
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line be pushed back on the input stream). It is sometimes useful to
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override this method in a subclass.
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\end{methoddesc}
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\begin{methoddesc}{islast}{line}
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Return true if the given line is a delimiter on which Message should
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stop. The delimiter line is consumed, and the file object's read
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location positioned immediately after it. By default this method just
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checks that the line is blank, but you can override it in a subclass.
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\end{methoddesc}
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\begin{methoddesc}{iscomment}{line}
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Return \code{True} if the given line should be ignored entirely, just skipped.
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By default this is a stub that always returns \code{False}, but you can
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override it in a subclass.
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\end{methoddesc}
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\begin{methoddesc}{getallmatchingheaders}{name}
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Return a list of lines consisting of all headers matching
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\var{name}, if any. Each physical line, whether it is a continuation
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line or not, is a separate list item. Return the empty list if no
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header matches \var{name}.
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\end{methoddesc}
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\begin{methoddesc}{getfirstmatchingheader}{name}
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Return a list of lines comprising the first header matching
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\var{name}, and its continuation line(s), if any. Return
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\code{None} if there is no header matching \var{name}.
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\end{methoddesc}
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\begin{methoddesc}{getrawheader}{name}
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Return a single string consisting of the text after the colon in the
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first header matching \var{name}. This includes leading whitespace,
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the trailing linefeed, and internal linefeeds and whitespace if there
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any continuation line(s) were present. Return \code{None} if there is
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no header matching \var{name}.
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\end{methoddesc}
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\begin{methoddesc}{getheader}{name\optional{, default}}
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Like \code{getrawheader(\var{name})}, but strip leading and trailing
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whitespace. Internal whitespace is not stripped. The optional
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\var{default} argument can be used to specify a different default to
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be returned when there is no header matching \var{name}.
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\end{methoddesc}
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\begin{methoddesc}{get}{name\optional{, default}}
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An alias for \method{getheader()}, to make the interface more compatible
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with regular dictionaries.
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\end{methoddesc}
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\begin{methoddesc}{getaddr}{name}
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Return a pair \code{(\var{full name}, \var{email address})} parsed
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from the string returned by \code{getheader(\var{name})}. If no
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header matching \var{name} exists, return \code{(None, None)};
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otherwise both the full name and the address are (possibly empty)
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strings.
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Example: If \var{m}'s first \mailheader{From} header contains the
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string \code{'jack@cwi.nl (Jack Jansen)'}, then
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\code{m.getaddr('From')} will yield the pair
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\code{('Jack Jansen', 'jack@cwi.nl')}.
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If the header contained
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\code{'Jack Jansen <jack@cwi.nl>'} instead, it would yield the
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exact same result.
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\end{methoddesc}
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\begin{methoddesc}{getaddrlist}{name}
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This is similar to \code{getaddr(\var{list})}, but parses a header
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containing a list of email addresses (e.g.\ a \mailheader{To} header) and
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returns a list of \code{(\var{full name}, \var{email address})} pairs
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(even if there was only one address in the header). If there is no
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header matching \var{name}, return an empty list.
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If multiple headers exist that match the named header (e.g. if there
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are several \mailheader{Cc} headers), all are parsed for addresses.
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Any continuation lines the named headers contain are also parsed.
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\end{methoddesc}
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\begin{methoddesc}{getdate}{name}
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Retrieve a header using \method{getheader()} and parse it into a 9-tuple
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compatible with \function{time.mktime()}; note that fields 6, 7, and 8
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are not usable. If there is no header matching
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\var{name}, or it is unparsable, return \code{None}.
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Date parsing appears to be a black art, and not all mailers adhere to
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the standard. While it has been tested and found correct on a large
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collection of email from many sources, it is still possible that this
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function may occasionally yield an incorrect result.
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\end{methoddesc}
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\begin{methoddesc}{getdate_tz}{name}
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Retrieve a header using \method{getheader()} and parse it into a
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10-tuple; the first 9 elements will make a tuple compatible with
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\function{time.mktime()}, and the 10th is a number giving the offset
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of the date's timezone from UTC. Note that fields 6, 7, and 8
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are not usable. Similarly to \method{getdate()}, if
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there is no header matching \var{name}, or it is unparsable, return
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\code{None}.
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\end{methoddesc}
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\class{Message} instances also support a limited mapping interface.
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In particular: \code{\var{m}[name]} is like
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\code{\var{m}.getheader(name)} but raises \exception{KeyError} if
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there is no matching header; and \code{len(\var{m})},
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\code{\var{m}.get(\var{name}\optional{\var{, default}})},
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\code{\var{m}.has_key(\var{name})}, \code{\var{m}.keys()},
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\code{\var{m}.values()} \code{\var{m}.items()}, and
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\code{\var{m}.setdefault(\var{name}\optional{\var{, default}})} act as
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expected, with the one difference that \method{setdefault()} uses
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an empty string as the default value. \class{Message} instances
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also support the mapping writable interface \code{\var{m}[name] =
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value} and \code{del \var{m}[name]}. \class{Message} objects do not
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support the \method{clear()}, \method{copy()}, \method{popitem()}, or
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\method{update()} methods of the mapping interface. (Support for
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\method{get()} and \method{setdefault()} was only added in Python
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2.2.)
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Finally, \class{Message} instances have some public instance variables:
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\begin{memberdesc}{headers}
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A list containing the entire set of header lines, in the order in
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which they were read (except that setitem calls may disturb this
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order). Each line contains a trailing newline. The
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blank line terminating the headers is not contained in the list.
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\end{memberdesc}
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\begin{memberdesc}{fp}
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The file or file-like object passed at instantiation time. This can
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be used to read the message content.
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\end{memberdesc}
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\begin{memberdesc}{unixfrom}
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The \UNIX{} \samp{From~} line, if the message had one, or an empty
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string. This is needed to regenerate the message in some contexts,
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such as an \code{mbox}-style mailbox file.
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\end{memberdesc}
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\subsection{AddressList Objects \label{addresslist-objects}}
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An \class{AddressList} instance has the following methods:
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\begin{methoddesc}{__len__}{}
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Return the number of addresses in the address list.
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\end{methoddesc}
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\begin{methoddesc}{__str__}{}
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Return a canonicalized string representation of the address list.
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Addresses are rendered in "name" <host@domain> form, comma-separated.
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\end{methoddesc}
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\begin{methoddesc}{__add__}{alist}
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Return a new \class{AddressList} instance that contains all addresses
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in both \class{AddressList} operands, with duplicates removed (set
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union).
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\end{methoddesc}
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\begin{methoddesc}{__iadd__}{alist}
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In-place version of \method{__add__()}; turns this \class{AddressList}
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instance into the union of itself and the right-hand instance,
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\var{alist}.
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\end{methoddesc}
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\begin{methoddesc}{__sub__}{alist}
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Return a new \class{AddressList} instance that contains every address
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in the left-hand \class{AddressList} operand that is not present in
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the right-hand address operand (set difference).
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\end{methoddesc}
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\begin{methoddesc}{__isub__}{alist}
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In-place version of \method{__sub__()}, removing addresses in this
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list which are also in \var{alist}.
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\end{methoddesc}
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Finally, \class{AddressList} instances have one public instance variable:
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\begin{memberdesc}{addresslist}
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A list of tuple string pairs, one per address. In each member, the
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first is the canonicalized name part, the second is the
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actual route-address (\character{@}-separated username-host.domain
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pair).
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\end{memberdesc}
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