You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
284 lines
14 KiB
284 lines
14 KiB
:mod:`email.generator`: Generating MIME documents
|
|
-------------------------------------------------
|
|
|
|
.. module:: email.generator
|
|
:synopsis: Generate flat text email messages from a message structure.
|
|
|
|
**Source code:** :source:`Lib/email/generator.py`
|
|
|
|
--------------
|
|
|
|
One of the most common tasks is to generate the flat (serialized) version of
|
|
the email message represented by a message object structure. You will need to
|
|
do this if you want to send your message via :meth:`smtplib.SMTP.sendmail` or
|
|
the :mod:`nntplib` module, or print the message on the console. Taking a
|
|
message object structure and producing a serialized representation is the job
|
|
of the generator classes.
|
|
|
|
As with the :mod:`email.parser` module, you aren't limited to the functionality
|
|
of the bundled generator; you could write one from scratch yourself. However
|
|
the bundled generator knows how to generate most email in a standards-compliant
|
|
way, should handle MIME and non-MIME email messages just fine, and is designed
|
|
so that the bytes-oriented parsing and generation operations are inverses,
|
|
assuming the same non-transforming :mod:`~email.policy` is used for both. That
|
|
is, parsing the serialized byte stream via the
|
|
:class:`~email.parser.BytesParser` class and then regenerating the serialized
|
|
byte stream using :class:`BytesGenerator` should produce output identical to
|
|
the input [#]_. (On the other hand, using the generator on an
|
|
:class:`~email.message.EmailMessage` constructed by program may result in
|
|
changes to the :class:`~email.message.EmailMessage` object as defaults are
|
|
filled in.)
|
|
|
|
The :class:`Generator` class can be used to flatten a message into a text (as
|
|
opposed to binary) serialized representation, but since Unicode cannot
|
|
represent binary data directly, the message is of necessity transformed into
|
|
something that contains only ASCII characters, using the standard email RFC
|
|
Content Transfer Encoding techniques for encoding email messages for transport
|
|
over channels that are not "8 bit clean".
|
|
|
|
To accommodate reproducible processing of SMIME-signed messages
|
|
:class:`Generator` disables header folding for message parts of type
|
|
``multipart/signed`` and all subparts.
|
|
|
|
|
|
.. class:: BytesGenerator(outfp, mangle_from_=None, maxheaderlen=None, *, \
|
|
policy=None)
|
|
|
|
Return a :class:`BytesGenerator` object that will write any message provided
|
|
to the :meth:`flatten` method, or any surrogateescape encoded text provided
|
|
to the :meth:`write` method, to the :term:`file-like object` *outfp*.
|
|
*outfp* must support a ``write`` method that accepts binary data.
|
|
|
|
If optional *mangle_from_* is ``True``, put a ``>`` character in front of
|
|
any line in the body that starts with the exact string ``"From "``, that is
|
|
``From`` followed by a space at the beginning of a line. *mangle_from_*
|
|
defaults to the value of the :attr:`~email.policy.Policy.mangle_from_`
|
|
setting of the *policy* (which is ``True`` for the
|
|
:data:`~email.policy.compat32` policy and ``False`` for all others).
|
|
*mangle_from_* is intended for use when messages are stored in unix mbox
|
|
format (see :mod:`mailbox` and `WHY THE CONTENT-LENGTH FORMAT IS BAD
|
|
<https://www.jwz.org/doc/content-length.html>`_).
|
|
|
|
If *maxheaderlen* is not ``None``, refold any header lines that are longer
|
|
than *maxheaderlen*, or if ``0``, do not rewrap any headers. If
|
|
*manheaderlen* is ``None`` (the default), wrap headers and other message
|
|
lines according to the *policy* settings.
|
|
|
|
If *policy* is specified, use that policy to control message generation. If
|
|
*policy* is ``None`` (the default), use the policy associated with the
|
|
:class:`~email.message.Message` or :class:`~email.message.EmailMessage`
|
|
object passed to ``flatten`` to control the message generation. See
|
|
:mod:`email.policy` for details on what *policy* controls.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
.. versionchanged:: 3.3 Added the *policy* keyword.
|
|
|
|
.. versionchanged:: 3.6 The default behavior of the *mangle_from_*
|
|
and *maxheaderlen* parameters is to follow the policy.
|
|
|
|
|
|
.. method:: flatten(msg, unixfrom=False, linesep=None)
|
|
|
|
Print the textual representation of the message object structure rooted
|
|
at *msg* to the output file specified when the :class:`BytesGenerator`
|
|
instance was created.
|
|
|
|
If the :mod:`~email.policy` option :attr:`~email.policy.Policy.cte_type`
|
|
is ``8bit`` (the default), copy any headers in the original parsed
|
|
message that have not been modified to the output with any bytes with the
|
|
high bit set reproduced as in the original, and preserve the non-ASCII
|
|
:mailheader:`Content-Transfer-Encoding` of any body parts that have them.
|
|
If ``cte_type`` is ``7bit``, convert the bytes with the high bit set as
|
|
needed using an ASCII-compatible :mailheader:`Content-Transfer-Encoding`.
|
|
That is, transform parts with non-ASCII
|
|
:mailheader:`Content-Transfer-Encoding`
|
|
(:mailheader:`Content-Transfer-Encoding: 8bit`) to an ASCII compatible
|
|
:mailheader:`Content-Transfer-Encoding`, and encode RFC-invalid non-ASCII
|
|
bytes in headers using the MIME ``unknown-8bit`` character set, thus
|
|
rendering them RFC-compliant.
|
|
|
|
.. XXX: There should be an option that just does the RFC
|
|
compliance transformation on headers but leaves CTE 8bit parts alone.
|
|
|
|
If *unixfrom* is ``True``, print the envelope header delimiter used by
|
|
the Unix mailbox format (see :mod:`mailbox`) before the first of the
|
|
:rfc:`5322` headers of the root message object. If the root object has
|
|
no envelope header, craft a standard one. The default is ``False``.
|
|
Note that for subparts, no envelope header is ever printed.
|
|
|
|
If *linesep* is not ``None``, use it as the separator character between
|
|
all the lines of the flattened message. If *linesep* is ``None`` (the
|
|
default), use the value specified in the *policy*.
|
|
|
|
.. XXX: flatten should take a *policy* keyword.
|
|
|
|
|
|
.. method:: clone(fp)
|
|
|
|
Return an independent clone of this :class:`BytesGenerator` instance with
|
|
the exact same option settings, and *fp* as the new *outfp*.
|
|
|
|
|
|
.. method:: write(s)
|
|
|
|
Encode *s* using the ``ASCII`` codec and the ``surrogateescape`` error
|
|
handler, and pass it to the *write* method of the *outfp* passed to the
|
|
:class:`BytesGenerator`'s constructor.
|
|
|
|
|
|
As a convenience, :class:`~email.message.EmailMessage` provides the methods
|
|
:meth:`~email.message.EmailMessage.as_bytes` and ``bytes(aMessage)`` (a.k.a.
|
|
:meth:`~email.message.EmailMessage.__bytes__`), which simplify the generation of
|
|
a serialized binary representation of a message object. For more detail, see
|
|
:mod:`email.message`.
|
|
|
|
|
|
Because strings cannot represent binary data, the :class:`Generator` class must
|
|
convert any binary data in any message it flattens to an ASCII compatible
|
|
format, by converting them to an ASCII compatible
|
|
:mailheader:`Content-Transfer_Encoding`. Using the terminology of the email
|
|
RFCs, you can think of this as :class:`Generator` serializing to an I/O stream
|
|
that is not "8 bit clean". In other words, most applications will want
|
|
to be using :class:`BytesGenerator`, and not :class:`Generator`.
|
|
|
|
.. class:: Generator(outfp, mangle_from_=None, maxheaderlen=None, *, \
|
|
policy=None)
|
|
|
|
Return a :class:`Generator` object that will write any message provided
|
|
to the :meth:`flatten` method, or any text provided to the :meth:`write`
|
|
method, to the :term:`file-like object` *outfp*. *outfp* must support a
|
|
``write`` method that accepts string data.
|
|
|
|
If optional *mangle_from_* is ``True``, put a ``>`` character in front of
|
|
any line in the body that starts with the exact string ``"From "``, that is
|
|
``From`` followed by a space at the beginning of a line. *mangle_from_*
|
|
defaults to the value of the :attr:`~email.policy.Policy.mangle_from_`
|
|
setting of the *policy* (which is ``True`` for the
|
|
:data:`~email.policy.compat32` policy and ``False`` for all others).
|
|
*mangle_from_* is intended for use when messages are stored in unix mbox
|
|
format (see :mod:`mailbox` and `WHY THE CONTENT-LENGTH FORMAT IS BAD
|
|
<https://www.jwz.org/doc/content-length.html>`_).
|
|
|
|
If *maxheaderlen* is not ``None``, refold any header lines that are longer
|
|
than *maxheaderlen*, or if ``0``, do not rewrap any headers. If
|
|
*manheaderlen* is ``None`` (the default), wrap headers and other message
|
|
lines according to the *policy* settings.
|
|
|
|
If *policy* is specified, use that policy to control message generation. If
|
|
*policy* is ``None`` (the default), use the policy associated with the
|
|
:class:`~email.message.Message` or :class:`~email.message.EmailMessage`
|
|
object passed to ``flatten`` to control the message generation. See
|
|
:mod:`email.policy` for details on what *policy* controls.
|
|
|
|
.. versionchanged:: 3.3 Added the *policy* keyword.
|
|
|
|
.. versionchanged:: 3.6 The default behavior of the *mangle_from_*
|
|
and *maxheaderlen* parameters is to follow the policy.
|
|
|
|
|
|
.. method:: flatten(msg, unixfrom=False, linesep=None)
|
|
|
|
Print the textual representation of the message object structure rooted
|
|
at *msg* to the output file specified when the :class:`Generator`
|
|
instance was created.
|
|
|
|
If the :mod:`~email.policy` option :attr:`~email.policy.Policy.cte_type`
|
|
is ``8bit``, generate the message as if the option were set to ``7bit``.
|
|
(This is required because strings cannot represent non-ASCII bytes.)
|
|
Convert any bytes with the high bit set as needed using an
|
|
ASCII-compatible :mailheader:`Content-Transfer-Encoding`. That is,
|
|
transform parts with non-ASCII :mailheader:`Content-Transfer-Encoding`
|
|
(:mailheader:`Content-Transfer-Encoding: 8bit`) to an ASCII compatible
|
|
:mailheader:`Content-Transfer-Encoding`, and encode RFC-invalid non-ASCII
|
|
bytes in headers using the MIME ``unknown-8bit`` character set, thus
|
|
rendering them RFC-compliant.
|
|
|
|
If *unixfrom* is ``True``, print the envelope header delimiter used by
|
|
the Unix mailbox format (see :mod:`mailbox`) before the first of the
|
|
:rfc:`5322` headers of the root message object. If the root object has
|
|
no envelope header, craft a standard one. The default is ``False``.
|
|
Note that for subparts, no envelope header is ever printed.
|
|
|
|
If *linesep* is not ``None``, use it as the separator character between
|
|
all the lines of the flattened message. If *linesep* is ``None`` (the
|
|
default), use the value specified in the *policy*.
|
|
|
|
.. XXX: flatten should take a *policy* keyword.
|
|
|
|
.. versionchanged:: 3.2
|
|
Added support for re-encoding ``8bit`` message bodies, and the
|
|
*linesep* argument.
|
|
|
|
|
|
.. method:: clone(fp)
|
|
|
|
Return an independent clone of this :class:`Generator` instance with the
|
|
exact same options, and *fp* as the new *outfp*.
|
|
|
|
|
|
.. method:: write(s)
|
|
|
|
Write *s* to the *write* method of the *outfp* passed to the
|
|
:class:`Generator`'s constructor. This provides just enough file-like
|
|
API for :class:`Generator` instances to be used in the :func:`print`
|
|
function.
|
|
|
|
|
|
As a convenience, :class:`~email.message.EmailMessage` provides the methods
|
|
:meth:`~email.message.EmailMessage.as_string` and ``str(aMessage)`` (a.k.a.
|
|
:meth:`~email.message.EmailMessage.__str__`), which simplify the generation of
|
|
a formatted string representation of a message object. For more detail, see
|
|
:mod:`email.message`.
|
|
|
|
|
|
The :mod:`email.generator` module also provides a derived class,
|
|
:class:`DecodedGenerator`, which is like the :class:`Generator` base class,
|
|
except that non-\ :mimetype:`text` parts are not serialized, but are instead
|
|
represented in the output stream by a string derived from a template filled
|
|
in with information about the part.
|
|
|
|
.. class:: DecodedGenerator(outfp, mangle_from_=None, maxheaderlen=None, \
|
|
fmt=None, *, policy=None)
|
|
|
|
Act like :class:`Generator`, except that for any subpart of the message
|
|
passed to :meth:`Generator.flatten`, if the subpart is of main type
|
|
:mimetype:`text`, print the decoded payload of the subpart, and if the main
|
|
type is not :mimetype:`text`, instead of printing it fill in the string
|
|
*fmt* using information from the part and print the resulting
|
|
filled-in string.
|
|
|
|
To fill in *fmt*, execute ``fmt % part_info``, where ``part_info``
|
|
is a dictionary composed of the following keys and values:
|
|
|
|
* ``type`` -- Full MIME type of the non-\ :mimetype:`text` part
|
|
|
|
* ``maintype`` -- Main MIME type of the non-\ :mimetype:`text` part
|
|
|
|
* ``subtype`` -- Sub-MIME type of the non-\ :mimetype:`text` part
|
|
|
|
* ``filename`` -- Filename of the non-\ :mimetype:`text` part
|
|
|
|
* ``description`` -- Description associated with the non-\ :mimetype:`text` part
|
|
|
|
* ``encoding`` -- Content transfer encoding of the non-\ :mimetype:`text` part
|
|
|
|
If *fmt* is ``None``, use the following default *fmt*:
|
|
|
|
"[Non-text (%(type)s) part of message omitted, filename %(filename)s]"
|
|
|
|
Optional *_mangle_from_* and *maxheaderlen* are as with the
|
|
:class:`Generator` base class.
|
|
|
|
|
|
.. rubric:: Footnotes
|
|
|
|
.. [#] This statement assumes that you use the appropriate setting for
|
|
``unixfrom``, and that there are no :mod:`policy` settings calling for
|
|
automatic adjustments (for example,
|
|
:attr:`~email.policy.Policy.refold_source` must be ``none``, which is
|
|
*not* the default). It is also not 100% true, since if the message
|
|
does not conform to the RFC standards occasionally information about the
|
|
exact original text is lost during parsing error recovery. It is a goal
|
|
to fix these latter edge cases when possible.
|