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\section{\module{email.Parser} ---
Parsing flat text email messages}
\declaremodule{standard}{email.Parser}
\modulesynopsis{Parse flat text email messages to produce a message
object tree.}
\sectionauthor{Barry A. Warsaw}{barry@zope.com}
\versionadded{2.2}
The \module{Parser} module provides a single class, the \class{Parser}
class, which is used to take a message in flat text form and create
the associated object model. The resulting object tree can then be
manipulated using the \class{Message} class interface as described in
\refmodule{email.Message}, and turned over
to a generator (as described in \refmodule{emamil.Generator}) to
return the textual representation of the message. It is intended that
the \class{Parser} to \class{Generator} path be idempotent if the
object model isn't modified in between.
\subsection{Parser class API}
\begin{classdesc}{Parser}{\optional{_class}}
The constructor for the \class{Parser} class takes a single optional
argument \var{_class}. This must be callable factory (i.e. a function
or a class), and it is used whenever a sub-message object needs to be
created. It defaults to \class{Message} (see
\refmodule{email.Message}). \var{_class} will be called with zero
arguments.
\end{classdesc}
The other public \class{Parser} methods are:
\begin{methoddesc}[Parser]{parse}{fp}
Read all the data from the file-like object \var{fp}, parse the
resulting text, and return the root message object. \var{fp} must
support both the \method{readline()} and the \method{read()} methods
on file-like objects.
The text contained in \var{fp} must be formatted as a block of \rfc{2822}
style headers and header continuation lines, optionally preceeded by a
\emph{Unix-From} header. The header block is terminated either by the
end of the data or by a blank line. Following the header block is the
body of the message (which may contain MIME-encoded subparts).
\end{methoddesc}
\begin{methoddesc}[Parser]{parsestr}{text}
Similar to the \method{parse()} method, except it takes a string
object instead of a file-like object. Calling this method on a string
is exactly equivalent to wrapping \var{text} in a \class{StringIO}
instance first and calling \method{parse()}.
\end{methoddesc}
Since creating a message object tree from a string or a file object is
such a common task, two functions are provided as a convenience. They
are available in the top-level \module{email} package namespace.
\begin{funcdesc}{message_from_string}{s\optional{, _class}}
Return a message object tree from a string. This is exactly
equivalent to \code{Parser().parsestr(s)}. Optional \var{_class} is
interpreted as with the \class{Parser} class constructor.
\end{funcdesc}
\begin{funcdesc}{message_from_file}{fp\optional{, _class}}
Return a message object tree from an open file object. This is exactly
equivalent to \code{Parser().parse(fp)}. Optional \var{_class} is
interpreted as with the \class{Parser} class constructor.
\end{funcdesc}
Here's an example of how you might use this at an interactive Python
prompt:
\begin{verbatim}
>>> import email
>>> msg = email.message_from_string(myString)
\end{verbatim}
\subsection{Additional notes}
Here are some notes on the parsing semantics:
\begin{itemize}
\item Most non-\code{multipart} type messages are parsed as a single
message object with a string payload. These objects will return
0 for \method{is_multipart()}.
\item One exception is for \code{message/delivery-status} type
messages. Because such the body of such messages consist of
blocks of headers, \class{Parser} will create a non-multipart
object containing non-multipart subobjects for each header
block.
\item Another exception is for \code{message/*} types (i.e. more
general than \code{message/delivery-status}. These are
typically \code{message/rfc822} type messages, represented as a
non-multipart object containing a singleton payload, another
non-multipart \class{Message} instance.
\end{itemize}
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