.. module:: email.contentmanager :synopsis: Storing and Retrieving Content from MIME Parts
.. moduleauthor:: R. David Murray <rdmurray@bitdance.com>
.. sectionauthor:: R. David Murray <rdmurray@bitdance.com>
Source code: :source:`Lib/email/contentmanager.py`
.. versionadded:: 3.6 [1]_
Base class for content managers. Provides the standard registry mechanisms
to register converters between MIME content and other representations, as
well as the get_content and set_content dispatch methods.
.. method:: get_content(msg, *args, **kw) Look up a handler function based on the ``mimetype`` of *msg* (see next paragraph), call it, passing through all arguments, and return the result of the call. The expectation is that the handler will extract the payload from *msg* and return an object that encodes information about the extracted data. To find the handler, look for the following keys in the registry, stopping with the first one found: * the string representing the full MIME type (``maintype/subtype``) * the string representing the ``maintype`` * the empty string If none of these keys produce a handler, raise a :exc:`KeyError` for the full MIME type.
.. method:: set_content(msg, obj, *args, **kw) If the ``maintype`` is ``multipart``, raise a :exc:`TypeError`; otherwise look up a handler function based on the type of *obj* (see next paragraph), call :meth:`~email.message.EmailMessage.clear_content` on the *msg*, and call the handler function, passing through all arguments. The expectation is that the handler will transform and store *obj* into *msg*, possibly making other changes to *msg* as well, such as adding various MIME headers to encode information needed to interpret the stored data. To find the handler, obtain the type of *obj* (``typ = type(obj)``), and look for the following keys in the registry, stopping with the first one found: * the type itself (``typ``) * the type's fully qualified name (``typ.__module__ + '.' + typ.__qualname__``). * the type's qualname (``typ.__qualname__``) * the type's name (``typ.__name__``). If none of the above match, repeat all of the checks above for each of the types in the :term:`MRO` (``typ.__mro__``). Finally, if no other key yields a handler, check for a handler for the key ``None``. If there is no handler for ``None``, raise a :exc:`KeyError` for the fully qualified name of the type. Also add a :mailheader:`MIME-Version` header if one is not present (see also :class:`.MIMEPart`).
.. method:: add_get_handler(key, handler) Record the function *handler* as the handler for *key*. For the possible values of *key*, see :meth:`get_content`.
.. method:: add_set_handler(typekey, handler) Record *handler* as the function to call when an object of a type matching *typekey* is passed to :meth:`set_content`. For the possible values of *typekey*, see :meth:`set_content`.
Currently the email package provides only one concrete content manager, :data:`raw_data_manager`, although more may be added in the future. :data:`raw_data_manager` is the :attr:`~email.policy.EmailPolicy.content_manager` provided by :attr:`~email.policy.EmailPolicy` and its derivatives.
.. data:: raw_data_manager This content manager provides only a minimum interface beyond that provided by :class:`~email.message.Message` itself: it deals only with text, raw byte strings, and :class:`~email.message.Message` objects. Nevertheless, it provides significant advantages compared to the base API: ``get_content`` on a text part will return a unicode string without the application needing to manually decode it, ``set_content`` provides a rich set of options for controlling the headers added to a part and controlling the content transfer encoding, and it enables the use of the various ``add_`` methods, thereby simplifying the creation of multipart messages. .. method:: get_content(msg, errors='replace') Return the payload of the part as either a string (for ``text`` parts), an :class:`~email.message.EmailMessage` object (for ``message/rfc822`` parts), or a ``bytes`` object (for all other non-multipart types). Raise a :exc:`KeyError` if called on a ``multipart``. If the part is a ``text`` part and *errors* is specified, use it as the error handler when decoding the payload to unicode. The default error handler is ``replace``. .. method:: set_content(msg, <'str'>, subtype="plain", charset='utf-8' \ cte=None, \ disposition=None, filename=None, cid=None, \ params=None, headers=None) set_content(msg, <'bytes'>, maintype, subtype, cte="base64", \ disposition=None, filename=None, cid=None, \ params=None, headers=None) set_content(msg, <'EmailMessage'>, cte=None, \ disposition=None, filename=None, cid=None, \ params=None, headers=None) Add headers and payload to *msg*: Add a :mailheader:`Content-Type` header with a ``maintype/subtype`` value. * For ``str``, set the MIME ``maintype`` to ``text``, and set the subtype to *subtype* if it is specified, or ``plain`` if it is not. * For ``bytes``, use the specified *maintype* and *subtype*, or raise a :exc:`TypeError` if they are not specified. * For :class:`~email.message.EmailMessage` objects, set the maintype to ``message``, and set the subtype to *subtype* if it is specified or ``rfc822`` if it is not. If *subtype* is ``partial``, raise an error (``bytes`` objects must be used to construct ``message/partial`` parts). If *charset* is provided (which is valid only for ``str``), encode the string to bytes using the specified character set. The default is ``utf-8``. If the specified *charset* is a known alias for a standard MIME charset name, use the standard charset instead. If *cte* is set, encode the payload using the specified content transfer encoding, and set the :mailheader:`Content-Transfer-Encoding` header to that value. Possible values for *cte* are ``quoted-printable``, ``base64``, ``7bit``, ``8bit``, and ``binary``. If the input cannot be encoded in the specified encoding (for example, specifying a *cte* of ``7bit`` for an input that contains non-ASCII values), raise a :exc:`ValueError`. * For ``str`` objects, if *cte* is not set use heuristics to determine the most compact encoding. * For :class:`~email.message.EmailMessage`, per :rfc:`2046`, raise an error if a *cte* of ``quoted-printable`` or ``base64`` is requested for *subtype* ``rfc822``, and for any *cte* other than ``7bit`` for *subtype* ``external-body``. For ``message/rfc822``, use ``8bit`` if *cte* is not specified. For all other values of *subtype*, use ``7bit``. .. note:: A *cte* of ``binary`` does not actually work correctly yet. The ``EmailMessage`` object as modified by ``set_content`` is correct, but :class:`~email.generator.BytesGenerator` does not serialize it correctly. If *disposition* is set, use it as the value of the :mailheader:`Content-Disposition` header. If not specified, and *filename* is specified, add the header with the value ``attachment``. If *disposition* is not specified and *filename* is also not specified, do not add the header. The only valid values for *disposition* are ``attachment`` and ``inline``. If *filename* is specified, use it as the value of the ``filename`` parameter of the :mailheader:`Content-Disposition` header. If *cid* is specified, add a :mailheader:`Content-ID` header with *cid* as its value. If *params* is specified, iterate its ``items`` method and use the resulting ``(key, value)`` pairs to set additional parameters on the :mailheader:`Content-Type` header. If *headers* is specified and is a list of strings of the form ``headername: headervalue`` or a list of ``header`` objects (distinguished from strings by having a ``name`` attribute), add the headers to *msg*.
Footnotes
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