mirror of
https://github.com/python/cpython.git
synced 2025-10-28 09:10:36 +00:00
320 lines
14 KiB
ReStructuredText
320 lines
14 KiB
ReStructuredText
:mod:`email.parser`: Parsing email messages
|
|
-------------------------------------------
|
|
|
|
.. module:: email.parser
|
|
:synopsis: Parse flat text email messages to produce a message object structure.
|
|
|
|
**Source code:** :source:`Lib/email/parser.py`
|
|
|
|
--------------
|
|
|
|
Message object structures can be created in one of two ways: they can be
|
|
created from whole cloth by creating an :class:`~email.message.EmailMessage`
|
|
object, adding headers using the dictionary interface, and adding payload(s)
|
|
using :meth:`~email.message.EmailMessage.set_content` and related methods, or
|
|
they can be created by parsing a serialized representation of the email
|
|
message.
|
|
|
|
The :mod:`email` package provides a standard parser that understands most email
|
|
document structures, including MIME documents. You can pass the parser a
|
|
bytes, string or file object, and the parser will return to you the root
|
|
:class:`~email.message.EmailMessage` 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 ``True`` from its :meth:`~email.message.EmailMessage.is_multipart`
|
|
method, and the subparts can be accessed via the payload manipulation methods,
|
|
such as :meth:`~email.message.EmailMessage.get_body`,
|
|
:meth:`~email.message.EmailMessage.iter_parts`, and
|
|
:meth:`~email.message.EmailMessage.walk`.
|
|
|
|
There are actually two parser interfaces available for use, the :class:`Parser`
|
|
API and the incremental :class:`FeedParser` API. The :class:`Parser` API is
|
|
most useful if you have the entire text of the message in memory, or if the
|
|
entire message lives in a file on the file system. :class:`FeedParser` is more
|
|
appropriate when you are reading the message from a stream which might block
|
|
waiting for more input (such as reading an email message from a socket). The
|
|
:class:`FeedParser` can consume and parse the message incrementally, and only
|
|
returns the root object when you close the parser.
|
|
|
|
Note that the parser can be extended in limited ways, and of course you can
|
|
implement your own parser completely from scratch. All of the logic that
|
|
connects the :mod:`email` package's bundled parser and the
|
|
:class:`~email.message.EmailMessage` class is embodied in the :mod:`policy`
|
|
class, so a custom parser can create message object trees any way it finds
|
|
necessary by implementing custom versions of the appropriate :mod:`policy`
|
|
methods.
|
|
|
|
|
|
FeedParser API
|
|
^^^^^^^^^^^^^^
|
|
|
|
The :class:`BytesFeedParser`, imported from the :mod:`email.feedparser` module,
|
|
provides an API that is conducive to incremental parsing of email messages,
|
|
such as would be necessary when reading the text of an email message from a
|
|
source that can block (such as a socket). The :class:`BytesFeedParser` can of
|
|
course be used to parse an email message fully contained in a :term:`bytes-like
|
|
object`, string, or file, but the :class:`BytesParser` API may be more
|
|
convenient for such use cases. The semantics and results of the two parser
|
|
APIs are identical.
|
|
|
|
The :class:`BytesFeedParser`'s API is simple; you create an instance, feed it a
|
|
bunch of bytes until there's no more to feed it, then close the parser to
|
|
retrieve the root message object. The :class:`BytesFeedParser` is extremely
|
|
accurate when parsing standards-compliant messages, and it does a very good job
|
|
of parsing non-compliant messages, providing information about how a message
|
|
was deemed broken. It will populate a message object's
|
|
:attr:`~email.message.EmailMessage.defects` attribute with a list of any
|
|
problems it found in a message. See the :mod:`email.errors` module for the
|
|
list of defects that it can find.
|
|
|
|
Here is the API for the :class:`BytesFeedParser`:
|
|
|
|
|
|
.. class:: BytesFeedParser(_factory=None, *, policy=policy.compat32)
|
|
|
|
Create a :class:`BytesFeedParser` instance. Optional *_factory* is a
|
|
no-argument callable; if not specified use the
|
|
:attr:`~email.policy.Policy.message_factory` from the *policy*. Call
|
|
*_factory* whenever a new message object is needed.
|
|
|
|
If *policy* is specified use the rules it specifies to update the
|
|
representation of the message. If *policy* is not set, use the
|
|
:class:`compat32 <email.policy.Compat32>` policy, which maintains backward
|
|
compatibility with the Python 3.2 version of the email package and provides
|
|
:class:`~email.message.Message` as the default factory. All other policies
|
|
provide :class:`~email.message.EmailMessage` as the default *_factory*. For
|
|
more information on what else *policy* controls, see the
|
|
:mod:`~email.policy` documentation.
|
|
|
|
Note: **The policy keyword should always be specified**; The default will
|
|
change to :data:`email.policy.default` in a future version of Python.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
.. versionchanged:: 3.3 Added the *policy* keyword.
|
|
.. versionchanged:: 3.6 *_factory* defaults to the policy ``message_factory``.
|
|
|
|
|
|
.. method:: feed(data)
|
|
|
|
Feed the parser some more data. *data* should be a :term:`bytes-like
|
|
object` containing one or more lines. The lines can be partial and the
|
|
parser will stitch such partial lines together properly. The lines can
|
|
have any of the three common line endings: carriage return, newline, or
|
|
carriage return and newline (they can even be mixed).
|
|
|
|
|
|
.. method:: close()
|
|
|
|
Complete the parsing of all previously fed data and return the root
|
|
message object. It is undefined what happens if :meth:`~feed` is called
|
|
after this method has been called.
|
|
|
|
|
|
.. class:: FeedParser(_factory=None, *, policy=policy.compat32)
|
|
|
|
Works like :class:`BytesFeedParser` except that the input to the
|
|
:meth:`~BytesFeedParser.feed` method must be a string. This is of limited
|
|
utility, since the only way for such a message to be valid is for it to
|
|
contain only ASCII text or, if :attr:`~email.policy.Policy.utf8` is
|
|
``True``, no binary attachments.
|
|
|
|
.. versionchanged:: 3.3 Added the *policy* keyword.
|
|
|
|
|
|
Parser API
|
|
^^^^^^^^^^
|
|
|
|
The :class:`BytesParser` class, imported from the :mod:`email.parser` module,
|
|
provides an API that can be used to parse a message when the complete contents
|
|
of the message are available in a :term:`bytes-like object` or file. The
|
|
:mod:`email.parser` module also provides :class:`Parser` for parsing strings,
|
|
and header-only parsers, :class:`BytesHeaderParser` and
|
|
:class:`HeaderParser`, which can be used if you're only interested in the
|
|
headers of the message. :class:`BytesHeaderParser` and :class:`HeaderParser`
|
|
can be much faster in these situations, since they do not attempt to parse the
|
|
message body, instead setting the payload to the raw body.
|
|
|
|
|
|
.. class:: BytesParser(_class=None, *, policy=policy.compat32)
|
|
|
|
Create a :class:`BytesParser` instance. The *_class* and *policy*
|
|
arguments have the same meaning and semantics as the *_factory*
|
|
and *policy* arguments of :class:`BytesFeedParser`.
|
|
|
|
Note: **The policy keyword should always be specified**; The default will
|
|
change to :data:`email.policy.default` in a future version of Python.
|
|
|
|
.. versionchanged:: 3.3
|
|
Removed the *strict* argument that was deprecated in 2.4. Added the
|
|
*policy* keyword.
|
|
.. versionchanged:: 3.6 *_class* defaults to the policy ``message_factory``.
|
|
|
|
|
|
.. method:: parse(fp, headersonly=False)
|
|
|
|
Read all the data from the binary file-like object *fp*, parse the
|
|
resulting bytes, and return the message object. *fp* must support
|
|
both the :meth:`~io.IOBase.readline` and the :meth:`~io.IOBase.read`
|
|
methods.
|
|
|
|
The bytes contained in *fp* must be formatted as a block of :rfc:`5322`
|
|
(or, if :attr:`~email.policy.Policy.utf8` is ``True``, :rfc:`6532`)
|
|
style headers and header continuation lines, optionally preceded by an
|
|
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, including subparts
|
|
with a :mailheader:`Content-Transfer-Encoding` of ``8bit``).
|
|
|
|
Optional *headersonly* is a flag specifying whether to stop parsing after
|
|
reading the headers or not. The default is ``False``, meaning it parses
|
|
the entire contents of the file.
|
|
|
|
|
|
.. method:: parsebytes(bytes, headersonly=False)
|
|
|
|
Similar to the :meth:`parse` method, except it takes a :term:`bytes-like
|
|
object` instead of a file-like object. Calling this method on a
|
|
:term:`bytes-like object` is equivalent to wrapping *bytes* in a
|
|
:class:`~io.BytesIO` instance first and calling :meth:`parse`.
|
|
|
|
Optional *headersonly* is as with the :meth:`parse` method.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. class:: BytesHeaderParser(_class=None, *, policy=policy.compat32)
|
|
|
|
Exactly like :class:`BytesParser`, except that *headersonly*
|
|
defaults to ``True``.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
|
|
.. class:: Parser(_class=None, *, policy=policy.compat32)
|
|
|
|
This class is parallel to :class:`BytesParser`, but handles string input.
|
|
|
|
.. versionchanged:: 3.3
|
|
Removed the *strict* argument. Added the *policy* keyword.
|
|
.. versionchanged:: 3.6 *_class* defaults to the policy ``message_factory``.
|
|
|
|
|
|
.. method:: parse(fp, headersonly=False)
|
|
|
|
Read all the data from the text-mode file-like object *fp*, parse the
|
|
resulting text, and return the root message object. *fp* must support
|
|
both the :meth:`~io.TextIOBase.readline` and the
|
|
:meth:`~io.TextIOBase.read` methods on file-like objects.
|
|
|
|
Other than the text mode requirement, this method operates like
|
|
:meth:`BytesParser.parse`.
|
|
|
|
|
|
.. method:: parsestr(text, headersonly=False)
|
|
|
|
Similar to the :meth:`parse` method, except it takes a string object
|
|
instead of a file-like object. Calling this method on a string is
|
|
equivalent to wrapping *text* in a :class:`~io.StringIO` instance first
|
|
and calling :meth:`parse`.
|
|
|
|
Optional *headersonly* is as with the :meth:`parse` method.
|
|
|
|
|
|
.. class:: HeaderParser(_class=None, *, policy=policy.compat32)
|
|
|
|
Exactly like :class:`Parser`, except that *headersonly*
|
|
defaults to ``True``.
|
|
|
|
|
|
Since creating a message object structure from a string or a file object is such
|
|
a common task, four functions are provided as a convenience. They are available
|
|
in the top-level :mod:`email` package namespace.
|
|
|
|
.. currentmodule:: email
|
|
|
|
|
|
.. function:: message_from_bytes(s, _class=None, *, policy=policy.compat32)
|
|
|
|
Return a message object structure from a :term:`bytes-like object`. This is
|
|
equivalent to ``BytesParser().parsebytes(s)``. Optional *_class* and
|
|
*policy* are interpreted as with the :class:`~email.parser.BytesParser` class
|
|
constructor.
|
|
|
|
.. versionadded:: 3.2
|
|
.. versionchanged:: 3.3
|
|
Removed the *strict* argument. Added the *policy* keyword.
|
|
|
|
|
|
.. function:: message_from_binary_file(fp, _class=None, *, \
|
|
policy=policy.compat32)
|
|
|
|
Return a message object structure tree from an open binary :term:`file
|
|
object`. This is equivalent to ``BytesParser().parse(fp)``. *_class* and
|
|
*policy* are interpreted as with the :class:`~email.parser.BytesParser` class
|
|
constructor.
|
|
|
|
.. versionadded:: 3.2
|
|
.. versionchanged:: 3.3
|
|
Removed the *strict* argument. Added the *policy* keyword.
|
|
|
|
|
|
.. function:: message_from_string(s, _class=None, *, policy=policy.compat32)
|
|
|
|
Return a message object structure from a string. This is equivalent to
|
|
``Parser().parsestr(s)``. *_class* and *policy* are interpreted as
|
|
with the :class:`~email.parser.Parser` class constructor.
|
|
|
|
.. versionchanged:: 3.3
|
|
Removed the *strict* argument. Added the *policy* keyword.
|
|
|
|
|
|
.. function:: message_from_file(fp, _class=None, *, policy=policy.compat32)
|
|
|
|
Return a message object structure tree from an open :term:`file object`.
|
|
This is equivalent to ``Parser().parse(fp)``. *_class* and *policy* are
|
|
interpreted as with the :class:`~email.parser.Parser` class constructor.
|
|
|
|
.. versionchanged:: 3.3
|
|
Removed the *strict* argument. Added the *policy* keyword.
|
|
.. versionchanged:: 3.6 *_class* defaults to the policy ``message_factory``.
|
|
|
|
|
|
Here's an example of how you might use :func:`message_from_bytes` at an
|
|
interactive Python prompt::
|
|
|
|
>>> import email
|
|
>>> msg = email.message_from_bytes(myBytes) # doctest: +SKIP
|
|
|
|
|
|
Additional notes
|
|
^^^^^^^^^^^^^^^^
|
|
|
|
Here are some notes on the parsing semantics:
|
|
|
|
* Most non-\ :mimetype:`multipart` type messages are parsed as a single message
|
|
object with a string payload. These objects will return ``False`` for
|
|
:meth:`~email.message.EmailMessage.is_multipart`, and
|
|
:meth:`~email.message.EmailMessage.iter_parts` will yield an empty list.
|
|
|
|
* 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 ``True`` for
|
|
:meth:`~email.message.EmailMessage.is_multipart`, and
|
|
:meth:`~email.message.EmailMessage.iter_parts` will yield a list of subparts.
|
|
|
|
* Most messages with a content type of :mimetype:`message/\*` (such as
|
|
:mimetype:`message/delivery-status` and :mimetype:`message/rfc822`) will also
|
|
be parsed as container object containing a list payload of length 1. Their
|
|
:meth:`~email.message.EmailMessage.is_multipart` method will return ``True``.
|
|
The single element yielded by :meth:`~email.message.EmailMessage.iter_parts`
|
|
will be a sub-message object.
|
|
|
|
* Some non-standards-compliant messages may not be internally consistent about
|
|
their :mimetype:`multipart`\ -edness. Such messages may have a
|
|
:mailheader:`Content-Type` header of type :mimetype:`multipart`, but their
|
|
:meth:`~email.message.EmailMessage.is_multipart` method may return ``False``.
|
|
If such messages were parsed with the :class:`~email.parser.FeedParser`,
|
|
they will have an instance of the
|
|
:class:`~email.errors.MultipartInvariantViolationDefect` class in their
|
|
*defects* attribute list. See :mod:`email.errors` for details.
|