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Updates do email package documentation for markup, style, and

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Barry Warsaw 2001-09-26 22:21:52 +00:00
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Doc/lib/email.tex
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@ -14,8 +14,9 @@
The \module{email} package is a library for managing email messages,
including MIME and other \rfc{2822}-based message documents. It
subsumes most of the functionality in several older standard modules
such as \module{rfc822}, \module{mimetools}, \module{multifile}, and
other non-standard packages such as \module{mimecntl}.
such as \refmodule{rfc822}, \refmodule{mimetools},
\refmodule{multifile}, and other non-standard packages such as
\module{mimecntl}.
The primary distinguishing feature of the \module{email} package is
that it splits the parsing and generating of email messages from the
@ -38,8 +39,8 @@ manipulated, and finally the model is rendered back into
flat text.
It is perfectly feasible to create the object model out of whole cloth
-- i.e. completely from scratch. From there, a similar progression can
be taken as above.
--- i.e. completely from scratch. From there, a similar progression
can be taken as above.
Also included are detailed specifications of all the classes and
modules that the \module{email} package provides, the exception
@ -49,76 +50,13 @@ some auxiliary utilities, and a few examples. For users of the older
descendent, a section on differences and porting is provided.
\subsection{Representing an email message}
The primary object in the \module{email} package is the
\class{Message} class, provided in the \refmodule{email.Message}
module. \class{Message} is the base class for the \module{email}
object model. It provides the core functionality for setting and
querying header fields, and for accessing message bodies.
Conceptually, a \class{Message} object consists of \emph{headers} and
\emph{payloads}. Headers are \rfc{2822} style field name and
values where the field name and value are separated by a colon. The
colon is not part of either the field name or the field value.
Headers are stored and returned in case-preserving form but are
matched case-insensitively. There may also be a single
\emph{Unix-From} header, also known as the envelope header or the
\mailheader{From_} header. The payload is either a string in the case of
simple message objects, a list of \class{Message} objects for
multipart MIME documents, or a single \class{Message} instance for
\mimetype{message/rfc822} type objects.
\class{Message} objects provide a mapping style interface for
accessing the message headers, and an explicit interface for accessing
both the headers and the payload. It provides convenience methods for
generating a flat text representation of the message object tree, for
accessing commonly used header parameters, and for recursively walking
over the object tree.
\input{emailmessage}
\subsection{Parsing email messages}
Message object trees can be created in one of two ways: they can be
created from whole cloth by instantiating \class{Message} objects and
stringing them together via \method{add_payload()} and
\method{set_payload()} calls, or they can be created by parsing a flat text
representation of the email message.
The \module{email} package provides a standard parser that understands
most email document structures, including MIME documents. You can
pass the parser a string or a file object, and the parser will return
to you the root \class{Message} instance of the object tree. For
simple, non-MIME messages the payload of this root object will likely
be a string (e.g. containing the text of the message). For MIME
messages, the root object will return 1 from its
\method{is_multipart()} method, and the subparts can be accessed via
the \method{get_payload()} and \method{walk()} methods.
Note that the parser can be extended in limited ways, and of course
you can implement your own parser completely from scratch. There is
no magical connection between the \module{email} package's bundled
parser and the
\class{Message} class, so your custom parser can create message object
trees in any way it find necessary. The \module{email} package's
parser is described in detail in the \refmodule{email.Parser} module
documentation.
\input{emailparser}
\subsection{Generating MIME documents}
One of the most common tasks is to generate the flat text of the email
message represented by a message object tree. You will need to do
this if you want to send your message via the \refmodule{smtplib}
module or the \refmodule{nntplib} module, or print the message on the
console. Taking a message object tree and producing a flat text
document is the job of the \refmodule{email.Generator} module.
Again, as with the \refmodule{email.Parser} module, you aren't limited
to the functionality of the bundled generator; you could write one
from scratch yourself. However the bundled generator knows how to
generate most email in a standards-compliant way, should handle MIME
and non-MIME email messages just fine, and is designed so that the
transformation from flat text, to an object tree via the
\class{Parser} class,
and back to flat text, be idempotent (the input is identical to the
output).
\input{emailgenerator}
\subsection{Creating email and MIME objects from scratch}
@ -156,9 +94,10 @@ of \class{MIMEBase}, although you could. \class{MIMEBase} is provided
primarily as a convenient base class for more specific MIME-aware
subclasses.
\var{_maintype} is the \code{Content-Type:} major type (e.g. \code{text} or
\code{image}), and \var{_subtype} is the \code{Content-Type:} minor type
(e.g. \code{plain} or \code{gif}). \var{_params} is a parameter
\var{_maintype} is the \mailheader{Content-Type} major type
(e.g. \mimetype{text} or \mimetype{image}), and \var{_subtype} is the
\mailheader{Content-Type} minor type
(e.g. \mimetype{plain} or \mimetype{gif}). \var{_params} is a parameter
key/value dictionary and is passed directly to
\method{Message.add_header()}.
@ -195,10 +134,11 @@ constructor.
\begin{classdesc}{MIMEText}{_text\optional{, _subtype\optional{,
_charset\optional{, _encoder}}}}
A subclass of \class{MIMEBase}, the \class{MIMEText} class is used to
create MIME objects of major type \mimetype{text}. \var{_text} is the string
for the payload. \var{_subtype} is the minor type and defaults to
\mimetype{plain}. \var{_charset} is the character set of the text and is
create MIME objects of major type \mimetype{text}. \var{_text} is the
string for the payload. \var{_subtype} is the minor type and defaults
to \mimetype{plain}. \var{_charset} is the character set of the text and is
passed as a parameter to the \class{MIMEBase} constructor; it defaults
to \code{us-ascii}. No guessing or encoding is performed on the text
data, but a newline is appended to \var{_text} if it doesn't already
@ -221,27 +161,24 @@ Optional \var{_subtype} sets the subtype of the message; it defaults
to \mimetype{rfc822}.
\end{classdesc}
\subsection{Encoders, Exceptions, Utilities, and Iterators}
\subsection{Encoders}
\input{emailencoders}
The \module{email} package provides various encoders for safe
transport of binary payloads in \class{MIMEImage} and \class{MIMEText}
instances. See the \refmodule{email.Encoders} module for more
details.
\subsection{Exception classes}
\input{emailexc}
All of the class exceptions that the \module{email} package can raise
are available in the \refmodule{email.Errors} module.
\subsection{Miscellaneous utilities}
\input{emailutil}
Some miscellaneous utility functions are available in the
\refmodule{email.Utils} module.
Iterating over a message object tree is easy with the
\method{Message.walk()} method; some additional helper iterators are
available in the \refmodule{email.Iterators} module.
\subsection{Iterators}
\input{emailiter}
\subsection{Differences from \module{mimelib}}
The \module{email} package was originally prototyped as a separate
library called \module{mimelib}. Changes have been made so that
library called
\ulink{\module{mimelib}}{http://mimelib.sf.net/}.
Changes have been made so that
method names are more consistent, and some methods or modules have
either been added or removed. The semantics of some of the methods
have also changed. For the most part, any functionality available in
@ -282,7 +219,7 @@ The \class{Message} class has the following differences:
\method{get_params()}.
Also, whereas \method{getparams()} returned a list of strings,
\method{get_params()} returns a list of 2-tuples, effectively
the key/value pairs of the parameters, split on the \samp{=}
the key/value pairs of the parameters, split on the \character{=}
sign.
\item The method \method{getparam()} was renamed to \method{get_param()}.
\item The method \method{getcharsets()} was renamed to
@ -355,4 +292,3 @@ function in the \refmodule{email.Iterators} module.
\subsection{Examples}
Coming soon...