#24277: The new email API is no longer provisional.

This is a wholesale reorganization and editing of the email documentation to
make the new API the standard one, and the old API the 'legacy' one.  The
default is still the compat32 policy, for backward compatibility.  We will
change that eventually.
This commit is contained in:
R David Murray 2016-09-07 21:15:59 -04:00
parent 23e8633781
commit 29d1bc0842
25 changed files with 2078 additions and 1670 deletions

View file

@ -8,190 +8,155 @@
--------------
Message object structures can be created in one of two ways: they can be created
from whole cloth by instantiating :class:`~email.message.Message` objects and
stringing them together via :meth:`~email.message.Message.attach` and
:meth:`~email.message.Message.set_payload` calls, or they
can be created by parsing a flat text representation of the email message.
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 string
or a file object, and the parser will return to you the root
:class:`~email.message.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 ``True`` from its :meth:`~email.message.Message.is_multipart` method, and
the subparts can be accessed via the :meth:`~email.message.Message.get_payload`
and :meth:`~email.message.Message.walk` methods.
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 classic
:class:`Parser` API and the incremental :class:`FeedParser` API. The classic
:class:`Parser` API is fine if you have the entire text of the message in memory
as a string, or if the entire message lives in a file on the file system.
:class:`FeedParser` is more appropriate for when you're reading the message from
a stream which might block waiting for more input (e.g. 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 [#]_.
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. There is no magical
connection between the :mod:`email` package's bundled parser and the
:class:`~email.message.Message` class, so your custom parser can create message
object trees any way it finds necessary.
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:`FeedParser`, 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 (e.g. a socket). The :class:`FeedParser` can of course be used
to parse an email message fully contained in a string or a file, but the classic
:class:`Parser` API may be more convenient for such use cases. The semantics
and results of the two parser APIs are identical.
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:`FeedParser`'s API is simple; you create an instance, feed it a bunch
of text until there's no more to feed it, then close the parser to retrieve the
root message object. The :class:`FeedParser` 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 *defects* attribute with a list of
any problems it found in a message. See the :mod:`email.errors` module for the
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:`FeedParser`:
Here is the API for the :class:`BytesFeedParser`:
.. class:: FeedParser(_factory=email.message.Message, *, policy=policy.compat32)
.. class:: BytesFeedParser(_factory=None, *, policy=policy.compat32)
Create a :class:`FeedParser` instance. Optional *_factory* is a no-argument
callable that will be called whenever a new message object is needed. It
defaults to the :class:`email.message.Message` class.
Create a :class:`BytesFeedParser` instance. Optional *_factory* is a
no-argument callable; if not specified determine the default based on the
*policy*. Call *_factory* whenever a new message object is needed.
If *policy* is specified (it must be an instance of a :mod:`~email.policy`
class) 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. For more information see the
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.
.. versionchanged:: 3.3 Added the *policy* keyword.
.. method:: feed(data)
Feed the :class:`FeedParser` some more data. *data* should be a string
containing one or more lines. The lines can be partial and the
:class:`FeedParser` will stitch such partial lines together properly. The
lines in the string can have any of the common three line endings,
carriage return, newline, or carriage return and newline (they can even be
mixed).
.. method:: close()
Closing a :class:`FeedParser` completes the parsing of all previously fed
data, and returns the root message object. It is undefined what happens
if you feed more data to a closed :class:`FeedParser`.
.. class:: BytesFeedParser(_factory=email.message.Message)
Works exactly like :class:`FeedParser` except that the input to the
:meth:`~FeedParser.feed` method must be bytes and not string.
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.
Parser class API
^^^^^^^^^^^^^^^^
The :class:`Parser` class, imported from the :mod:`email.parser` module,
.. 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 string or file. The :mod:`email.parser`
module also provides header-only parsers, called :class:`HeaderParser` and
:class:`BytesHeaderParser`, which can be used if you're only interested in the
headers of the message. :class:`HeaderParser` and :class:`BytesHeaderParser`
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 as a string. They
have the same API as the :class:`Parser` and :class:`BytesParser` classes.
.. versionadded:: 3.3
The BytesHeaderParser class.
message body, instead setting the payload to the raw body.
.. class:: Parser(_class=email.message.Message, *, policy=policy.compat32)
.. class:: BytesParser(_class=None, *, policy=policy.compat32)
The constructor for the :class:`Parser` class takes an optional argument
*_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:`~email.message.Message` (see :mod:`email.message`). The factory will
be called without arguments.
Create a :class:`BytesParser` instance. The *_class* and *policy*
arguments have the same meaning and sematnics as the *_factory*
and *policy* arguments of :class:`BytesFeedParser`.
If *policy* is specified (it must be an instance of a :mod:`~email.policy`
class) 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. For more information 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.
.. versionchanged:: 3.3
Removed the *strict* argument that was deprecated in 2.4. Added the
*policy* keyword.
The other public :class:`Parser` methods are:
.. method:: parse(fp, headersonly=False)
Read all the data from the 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.
The text contained in *fp* must be formatted as a block of :rfc:`2822`
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).
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:: 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 exactly
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:: BytesParser(_class=email.message.Message, *, policy=policy.compat32)
This class is exactly parallel to :class:`Parser`, but handles bytes input.
The *_class* and *strict* arguments are interpreted in the same way as for
the :class:`Parser` constructor.
If *policy* is specified (it must be an instance of a :mod:`~email.policy`
class) 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. For more information see the
:mod:`~email.policy` documentation.
.. versionchanged:: 3.3
Removed the *strict* argument. Added the *policy* keyword.
.. 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 on file-like objects.
methods.
The bytes contained in *fp* must be formatted as a block of :rfc:`2822`
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
@ -202,73 +167,122 @@ have the same API as the :class:`Parser` and :class:`BytesParser` classes.
reading the headers or not. The default is ``False``, meaning it parses
the entire contents of the file.
.. method:: parsebytes(text, headersonly=False)
.. 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 is equivalent
to wrapping *text* in a :class:`~io.BytesIO` instance first and calling
:meth:`parse`.
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.
.. 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_string(s, _class=email.message.Message, *, \
.. 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
*strict* 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 exactly equivalent to
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_bytes(s, _class=email.message.Message, *, \
policy=policy.compat32)
Return a message object structure from a :term:`bytes-like object`. This is exactly
equivalent to ``BytesParser().parsebytes(s)``. Optional *_class* and
*strict* are interpreted as with the :class:`~email.parser.Parser` class
constructor.
.. versionadded:: 3.2
.. versionchanged:: 3.3
Removed the *strict* argument. Added the *policy* keyword.
.. function:: message_from_file(fp, _class=email.message.Message, *, \
.. function:: message_from_file(fp, _class=None, *, \
policy=policy.compat32)
Return a message object structure tree from an open :term:`file object`.
This is exactly equivalent to ``Parser().parse(fp)``. *_class*
and *policy* are interpreted as with the :class:`~email.parser.Parser` class
constructor.
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.
.. function:: message_from_binary_file(fp, _class=email.message.Message, *, \
policy=policy.compat32)
Return a message object structure tree from an open binary :term:`file
object`. This is exactly equivalent to ``BytesParser().parse(fp)``.
*_class* and *policy* are interpreted as with the
:class:`~email.parser.Parser` class constructor.
.. versionadded:: 3.2
.. versionchanged:: 3.3
Removed the *strict* argument. Added the *policy* keyword.
Here's an example of how you might use this at an interactive Python prompt::
Here's an example of how you might use :func:`message_from_bytes` at an
interactive Python prompt::
>>> import email
>>> msg = email.message_from_string(myString) # doctest: +SKIP
>>> msg = email.message_from_bytes(myBytes) # doctest: +SKIP
Additional notes
@ -278,35 +292,27 @@ 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.Message.is_multipart`. Their
:meth:`~email.message.Message.get_payload` method will return a string object.
: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.Message.is_multipart` and their
:meth:`~email.message.Message.get_payload` method will return the list of
:class:`~email.message.Message` subparts.
: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/\*` (e.g.
: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.Message.is_multipart` method will return ``True``.
The single element in the list payload will be a sub-message object.
* 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
* 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.Message.is_multipart` method may return ``False``.
: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.
.. rubric:: Footnotes
.. [#] As of email package version 3.0, introduced in Python 2.4, the classic
:class:`~email.parser.Parser` was re-implemented in terms of the
:class:`~email.parser.FeedParser`, so the semantics and results are
identical between the two parsers.