: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`:

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.

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.

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