mirror of
https://github.com/python/cpython.git
synced 2025-10-31 05:31:20 +00:00
152 lines
6.8 KiB
TeX
152 lines
6.8 KiB
TeX
\declaremodule{standard}{email.Parser}
|
|
\modulesynopsis{Parse flat text email messages to produce a message
|
|
object structure.}
|
|
|
|
Message object structures 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{attach()} 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 structure. For
|
|
simple, non-MIME messages the payload of this root object will likely
|
|
be a string containing the text of the message. For MIME
|
|
messages, the root object will return \code{True} 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 any way it finds necessary.
|
|
|
|
The primary parser class is \class{Parser} which parses both the
|
|
headers and the payload of the message. In the case of
|
|
\mimetype{multipart} messages, it will recursively parse the body of
|
|
the container message. Two modes of parsing are supported,
|
|
\emph{strict} parsing, which will usually reject any non-RFC compliant
|
|
message, and \emph{lax} parsing, which attempts to adjust for common
|
|
MIME formatting problems.
|
|
|
|
The \module{email.Parser} module also provides a second class, called
|
|
\class{HeaderParser} which can be used if you're only interested in
|
|
the headers of the message. \class{HeaderParser} can be much faster in
|
|
these situations, since it does not attempt to parse the message body,
|
|
instead setting the payload to the raw body as a string.
|
|
\class{HeaderParser} has the same API as the \class{Parser} class.
|
|
|
|
\subsubsection{Parser class API}
|
|
|
|
\begin{classdesc}{Parser}{\optional{_class\optional{, strict}}}
|
|
The constructor for the \class{Parser} class takes an optional
|
|
argument \var{_class}. This must be a callable factory (such as 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}). The factory will be called without
|
|
arguments.
|
|
|
|
The optional \var{strict} flag specifies whether strict or lax parsing
|
|
should be performed. Normally, when things like MIME terminating
|
|
boundaries are missing, or when messages contain other formatting
|
|
problems, the \class{Parser} will raise a
|
|
\exception{MessageParseError}. However, when lax parsing is enabled,
|
|
the \class{Parser} will attempt to work around such broken formatting
|
|
to produce a usable message structure (this doesn't mean
|
|
\exception{MessageParseError}s are never raised; some ill-formatted
|
|
messages just can't be parsed). The \var{strict} flag defaults to
|
|
\code{False} since lax parsing usually provides the most convenient
|
|
behavior.
|
|
|
|
\versionchanged[The \var{strict} flag was added]{2.2.2}
|
|
\end{classdesc}
|
|
|
|
The other public \class{Parser} methods are:
|
|
|
|
\begin{methoddesc}[Parser]{parse}{fp\optional{, headersonly}}
|
|
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 preceded by a
|
|
envelope 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).
|
|
|
|
Optional \var{headersonly} is as with the \method{parse()} method.
|
|
|
|
\versionchanged[The \var{headersonly} flag was added]{2.2.2}
|
|
\end{methoddesc}
|
|
|
|
\begin{methoddesc}[Parser]{parsestr}{text\optional{, headersonly}}
|
|
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()}.
|
|
|
|
Optional \var{headersonly} is a flag specifying whether to stop
|
|
parsing after reading the headers or not. The default is \code{False},
|
|
meaning it parses the entire contents of the file.
|
|
|
|
\versionchanged[The \var{headersonly} flag was added]{2.2.2}
|
|
\end{methoddesc}
|
|
|
|
Since creating a message object structure 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\optional{, strict}}}
|
|
Return a message object structure from a string. This is exactly
|
|
equivalent to \code{Parser().parsestr(s)}. Optional \var{_class} and
|
|
\var{strict} are interpreted as with the \class{Parser} class constructor.
|
|
|
|
\versionchanged[The \var{strict} flag was added]{2.2.2}
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{message_from_file}{fp\optional{, _class\optional{, strict}}}
|
|
Return a message object structure tree from an open file object. This
|
|
is exactly equivalent to \code{Parser().parse(fp)}. Optional
|
|
\var{_class} and \var{strict} are interpreted as with the
|
|
\class{Parser} class constructor.
|
|
|
|
\versionchanged[The \var{strict} flag was added]{2.2.2}
|
|
\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}
|
|
|
|
\subsubsection{Additional notes}
|
|
|
|
Here are some notes on the parsing semantics:
|
|
|
|
\begin{itemize}
|
|
\item Most non-\mimetype{multipart} type messages are parsed as a single
|
|
message object with a string payload. These objects will return
|
|
\code{False} for \method{is_multipart()}. Their
|
|
\method{get_payload()} method will return a string object.
|
|
|
|
\item All \mimetype{multipart} type messages will be parsed as a
|
|
container message object with a list of sub-message objects for
|
|
their payload. The outer container message will return
|
|
\code{True} for \method{is_multipart()} and their
|
|
\method{get_payload()} method will return the list of
|
|
\class{Message} subparts.
|
|
|
|
\item Most messages with a content type of \mimetype{message/*}
|
|
(e.g. \mimetype{message/deliver-status} and
|
|
\mimetype{message/rfc822}) will also be parsed as container
|
|
object containing a list payload of length 1. Their
|
|
\method{is_multipart()} method will return \code{True}. The
|
|
single element in the list payload will be a sub-message object.
|
|
\end{itemize}
|