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113 lines
5.1 KiB
ReStructuredText
113 lines
5.1 KiB
ReStructuredText
:mod:`email`: Generating MIME documents
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---------------------------------------
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.. module:: email.generator
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:synopsis: Generate flat text email messages from a message structure.
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One of the most common tasks is to generate the flat text of the email message
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represented by a message object structure. You will need to do this if you want
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to send your message via the :mod:`smtplib` module or the :mod:`nntplib` module,
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or print the message on the console. Taking a message object structure and
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producing a flat text document is the job of the :class:`Generator` class.
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Again, as with the :mod:`email.parser` module, you aren't limited to the
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functionality of the bundled generator; you could write one from scratch
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yourself. However the bundled generator knows how to generate most email in a
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standards-compliant way, should handle MIME and non-MIME email messages just
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fine, and is designed so that the transformation from flat text, to a message
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structure via the :class:`Parser` class, and back to flat text, is idempotent
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(the input is identical to the output).
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Here are the public methods of the :class:`Generator` class, imported from the
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:mod:`email.generator` module:
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.. class:: Generator(outfp[, mangle_from_[, maxheaderlen]])
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The constructor for the :class:`Generator` class takes a file-like object called
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*outfp* for an argument. *outfp* must support the :meth:`write` method and be
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usable as the output file for the :func:`print` function.
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Optional *mangle_from_* is a flag that, when ``True``, puts a ``>`` character in
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front of any line in the body that starts exactly as ``From``, i.e. ``From``
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followed by a space at the beginning of the line. This is the only guaranteed
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portable way to avoid having such lines be mistaken for a Unix mailbox format
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envelope header separator (see `WHY THE CONTENT-LENGTH FORMAT IS BAD
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<http://www.jwz.org/doc/content-length.html>`_ for details). *mangle_from_*
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defaults to ``True``, but you might want to set this to ``False`` if you are not
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writing Unix mailbox format files.
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Optional *maxheaderlen* specifies the longest length for a non-continued header.
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When a header line is longer than *maxheaderlen* (in characters, with tabs
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expanded to 8 spaces), the header will be split as defined in the
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:mod:`email.header.Header` class. Set to zero to disable header wrapping. The
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default is 78, as recommended (but not required) by :rfc:`2822`.
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The other public :class:`Generator` methods are:
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.. method:: Generator.flatten(msg[, unixfrom])
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Print the textual representation of the message object structure rooted at *msg*
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to the output file specified when the :class:`Generator` instance was created.
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Subparts are visited depth-first and the resulting text will be properly MIME
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encoded.
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Optional *unixfrom* is a flag that forces the printing of the envelope header
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delimiter before the first :rfc:`2822` header of the root message object. If
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the root object has no envelope header, a standard one is crafted. By default,
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this is set to ``False`` to inhibit the printing of the envelope delimiter.
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Note that for subparts, no envelope header is ever printed.
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.. method:: Generator.clone(fp)
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Return an independent clone of this :class:`Generator` instance with the exact
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same options.
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.. method:: Generator.write(s)
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Write the string *s* to the underlying file object, i.e. *outfp* passed to
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:class:`Generator`'s constructor. This provides just enough file-like API for
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:class:`Generator` instances to be used in the :func:`print` function.
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As a convenience, see the methods :meth:`Message.as_string` and
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``str(aMessage)``, a.k.a. :meth:`Message.__str__`, which simplify the generation
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of a formatted string representation of a message object. For more detail, see
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:mod:`email.message`.
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The :mod:`email.generator` module also provides a derived class, called
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:class:`DecodedGenerator` which is like the :class:`Generator` base class,
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except that non-\ :mimetype:`text` parts are substituted with a format string
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representing the part.
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.. class:: DecodedGenerator(outfp[, mangle_from_[, maxheaderlen[, fmt]]])
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This class, derived from :class:`Generator` walks through all the subparts of a
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message. If the subpart is of main type :mimetype:`text`, then it prints the
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decoded payload of the subpart. Optional *_mangle_from_* and *maxheaderlen* are
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as with the :class:`Generator` base class.
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If the subpart is not of main type :mimetype:`text`, optional *fmt* is a format
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string that is used instead of the message payload. *fmt* is expanded with the
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following keywords, ``%(keyword)s`` format:
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* ``type`` -- Full MIME type of the non-\ :mimetype:`text` part
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* ``maintype`` -- Main MIME type of the non-\ :mimetype:`text` part
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* ``subtype`` -- Sub-MIME type of the non-\ :mimetype:`text` part
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* ``filename`` -- Filename of the non-\ :mimetype:`text` part
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* ``description`` -- Description associated with the non-\ :mimetype:`text` part
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* ``encoding`` -- Content transfer encoding of the non-\ :mimetype:`text` part
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The default value for *fmt* is ``None``, meaning ::
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[Non-text (%(type)s) part of message omitted, filename %(filename)s]
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