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564 lines
24 KiB
ReStructuredText
564 lines
24 KiB
ReStructuredText
:mod:`email`: Representing an email message
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-------------------------------------------
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.. module:: email.message
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:synopsis: The base class representing email messages.
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The central class in the :mod:`email` package is the :class:`Message` class,
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imported from the :mod:`email.message` module. It is the base class for the
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:mod:`email` object model. :class:`Message` provides the core functionality for
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setting and querying header fields, and for accessing message bodies.
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Conceptually, a :class:`Message` object consists of *headers* and *payloads*.
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Headers are :rfc:`2822` style field names and values where the field name and
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value are separated by a colon. The colon is not part of either the field name
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or the field value.
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Headers are stored and returned in case-preserving form but are matched
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case-insensitively. There may also be a single envelope header, also known as
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the *Unix-From* header or the ``From_`` header. The payload is either a string
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in the case of simple message objects or a list of :class:`Message` objects for
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MIME container documents (e.g. :mimetype:`multipart/\*` and
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:mimetype:`message/rfc822`).
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:class:`Message` objects provide a mapping style interface for accessing the
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message headers, and an explicit interface for accessing both the headers and
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the payload. It provides convenience methods for generating a flat text
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representation of the message object tree, for accessing commonly used header
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parameters, and for recursively walking over the object tree.
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Here are the methods of the :class:`Message` class:
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.. class:: Message()
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The constructor takes no arguments.
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.. method:: as_string(unixfrom=False, maxheaderlen=0)
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Return the entire message flattened as a string. When optional *unixfrom*
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is ``True``, the envelope header is included in the returned string.
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*unixfrom* defaults to ``False``. Flattening the message may trigger
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changes to the :class:`Message` if defaults need to be filled in to
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complete the transformation to a string (for example, MIME boundaries may
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be generated or modified).
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Note that this method is provided as a convenience and may not always
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format the message the way you want. For example, by default it does
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not do the mangling of lines that begin with ``From`` that is
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required by the unix mbox format. For more flexibility, instantiate a
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:class:`~email.generator.Generator` instance and use its :meth:`flatten`
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method directly. For example::
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from io import StringIO
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from email.generator import Generator
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fp = StringIO()
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g = Generator(fp, mangle_from_=True, maxheaderlen=60)
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g.flatten(msg)
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text = fp.getvalue()
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.. method:: __str__()
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Equivalent to ``as_string(unixfrom=True)``.
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.. method:: is_multipart()
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Return ``True`` if the message's payload is a list of sub-\
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:class:`Message` objects, otherwise return ``False``. When
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:meth:`is_multipart` returns False, the payload should be a string object.
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.. method:: set_unixfrom(unixfrom)
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Set the message's envelope header to *unixfrom*, which should be a string.
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.. method:: get_unixfrom()
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Return the message's envelope header. Defaults to ``None`` if the
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envelope header was never set.
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.. method:: attach(payload)
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Add the given *payload* to the current payload, which must be ``None`` or
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a list of :class:`Message` objects before the call. After the call, the
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payload will always be a list of :class:`Message` objects. If you want to
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set the payload to a scalar object (e.g. a string), use
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:meth:`set_payload` instead.
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.. method:: get_payload(i=None, decode=False)
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Return the current payload, which will be a list of
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:class:`Message` objects when :meth:`is_multipart` is ``True``, or a
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string when :meth:`is_multipart` is ``False``. If the payload is a list
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and you mutate the list object, you modify the message's payload in place.
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With optional argument *i*, :meth:`get_payload` will return the *i*-th
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element of the payload, counting from zero, if :meth:`is_multipart` is
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``True``. An :exc:`IndexError` will be raised if *i* is less than 0 or
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greater than or equal to the number of items in the payload. If the
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payload is a string (i.e. :meth:`is_multipart` is ``False``) and *i* is
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given, a :exc:`TypeError` is raised.
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Optional *decode* is a flag indicating whether the payload should be
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decoded or not, according to the :mailheader:`Content-Transfer-Encoding`
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header. When ``True`` and the message is not a multipart, the payload will
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be decoded if this header's value is ``quoted-printable`` or ``base64``.
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If some other encoding is used, or :mailheader:`Content-Transfer-Encoding`
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header is missing, or if the payload has bogus base64 data, the payload is
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returned as-is (undecoded). In all cases the returned value is binary
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data. If the message is a multipart and the *decode* flag is ``True``,
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then ``None`` is returned.
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When *decode* is ``False`` (the default) the body is returned as a string
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without decoding the :mailheader:`Content-Transfer-Encoding`. However,
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for a :mailheader:`Content-Transfer-Encoding` of 8bit, an attempt is made
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to decode the original bytes using the ``charset`` specified by the
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:mailheader:`Content-Type` header, using the ``replace`` error handler.
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If no ``charset`` is specified, or if the ``charset`` given is not
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recognized by the email package, the body is decoded using the default
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ASCII charset.
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.. method:: set_payload(payload, charset=None)
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Set the entire message object's payload to *payload*. It is the client's
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responsibility to ensure the payload invariants. Optional *charset* sets
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the message's default character set; see :meth:`set_charset` for details.
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.. method:: set_charset(charset)
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Set the character set of the payload to *charset*, which can either be a
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:class:`~email.charset.Charset` instance (see :mod:`email.charset`), a
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string naming a character set, or ``None``. If it is a string, it will
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be converted to a :class:`~email.charset.Charset` instance. If *charset*
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is ``None``, the ``charset`` parameter will be removed from the
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:mailheader:`Content-Type` header (the message will not be otherwise
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modified). Anything else will generate a :exc:`TypeError`.
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If there is no existing :mailheader:`MIME-Version` header one will be
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added. If there is no existing :mailheader:`Content-Type` header, one
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will be added with a value of :mimetype:`text/plain`. Whether the
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:mailheader:`Content-Type` header already exists or not, its ``charset``
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parameter will be set to *charset.output_charset*. If
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*charset.input_charset* and *charset.output_charset* differ, the payload
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will be re-encoded to the *output_charset*. If there is no existing
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:mailheader:`Content-Transfer-Encoding` header, then the payload will be
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transfer-encoded, if needed, using the specified
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:class:`~email.charset.Charset`, and a header with the appropriate value
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will be added. If a :mailheader:`Content-Transfer-Encoding` header
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already exists, the payload is assumed to already be correctly encoded
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using that :mailheader:`Content-Transfer-Encoding` and is not modified.
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.. method:: get_charset()
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Return the :class:`~email.charset.Charset` instance associated with the
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message's payload.
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The following methods implement a mapping-like interface for accessing the
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message's :rfc:`2822` headers. Note that there are some semantic differences
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between these methods and a normal mapping (i.e. dictionary) interface. For
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example, in a dictionary there are no duplicate keys, but here there may be
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duplicate message headers. Also, in dictionaries there is no guaranteed
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order to the keys returned by :meth:`keys`, but in a :class:`Message` object,
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headers are always returned in the order they appeared in the original
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message, or were added to the message later. Any header deleted and then
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re-added are always appended to the end of the header list.
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These semantic differences are intentional and are biased toward maximal
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convenience.
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Note that in all cases, any envelope header present in the message is not
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included in the mapping interface.
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In a model generated from bytes, any header values that (in contravention of
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the RFCs) contain non-ASCII bytes will, when retrieved through this
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interface, be represented as :class:`~email.header.Header` objects with
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a charset of `unknown-8bit`.
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.. method:: __len__()
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Return the total number of headers, including duplicates.
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.. method:: __contains__(name)
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Return true if the message object has a field named *name*. Matching is
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done case-insensitively and *name* should not include the trailing colon.
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Used for the ``in`` operator, e.g.::
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if 'message-id' in myMessage:
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print('Message-ID:', myMessage['message-id'])
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.. method:: __getitem__(name)
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Return the value of the named header field. *name* should not include the
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colon field separator. If the header is missing, ``None`` is returned; a
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:exc:`KeyError` is never raised.
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Note that if the named field appears more than once in the message's
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headers, exactly which of those field values will be returned is
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undefined. Use the :meth:`get_all` method to get the values of all the
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extant named headers.
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.. method:: __setitem__(name, val)
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Add a header to the message with field name *name* and value *val*. The
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field is appended to the end of the message's existing fields.
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Note that this does *not* overwrite or delete any existing header with the same
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name. If you want to ensure that the new header is the only one present in the
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message with field name *name*, delete the field first, e.g.::
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del msg['subject']
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msg['subject'] = 'Python roolz!'
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.. method:: __delitem__(name)
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Delete all occurrences of the field with name *name* from the message's
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headers. No exception is raised if the named field isn't present in the
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headers.
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.. method:: keys()
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Return a list of all the message's header field names.
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.. method:: values()
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Return a list of all the message's field values.
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.. method:: items()
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Return a list of 2-tuples containing all the message's field headers and
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values.
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.. method:: get(name, failobj=None)
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Return the value of the named header field. This is identical to
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:meth:`__getitem__` except that optional *failobj* is returned if the
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named header is missing (defaults to ``None``).
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Here are some additional useful methods:
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.. method:: get_all(name, failobj=None)
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Return a list of all the values for the field named *name*. If there are
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no such named headers in the message, *failobj* is returned (defaults to
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``None``).
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.. method:: add_header(_name, _value, **_params)
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Extended header setting. This method is similar to :meth:`__setitem__`
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except that additional header parameters can be provided as keyword
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arguments. *_name* is the header field to add and *_value* is the
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*primary* value for the header.
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For each item in the keyword argument dictionary *_params*, the key is
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taken as the parameter name, with underscores converted to dashes (since
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dashes are illegal in Python identifiers). Normally, the parameter will
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be added as ``key="value"`` unless the value is ``None``, in which case
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only the key will be added. If the value contains non-ASCII characters,
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it can be specified as a three tuple in the format
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``(CHARSET, LANGUAGE, VALUE)``, where ``CHARSET`` is a string naming the
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charset to be used to encode the value, ``LANGUAGE`` can usually be set
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to ``None`` or the empty string (see :rfc:`2231` for other possibilities),
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and ``VALUE`` is the string value containing non-ASCII code points. If
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a three tuple is not passed and the value contains non-ASCII characters,
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it is automatically encoded in :rfc:`2231` format using a ``CHARSET``
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of ``utf-8`` and a ``LANGUAGE`` of ``None``.
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Here's an example::
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msg.add_header('Content-Disposition', 'attachment', filename='bud.gif')
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This will add a header that looks like ::
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Content-Disposition: attachment; filename="bud.gif"
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An example with non-ASCII characters::
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msg.add_header('Content-Disposition', 'attachment',
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filename=('iso-8859-1', '', 'Fußballer.ppt'))
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Which produces ::
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Content-Disposition: attachment; filename*="iso-8859-1''Fu%DFballer.ppt"
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.. method:: replace_header(_name, _value)
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Replace a header. Replace the first header found in the message that
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matches *_name*, retaining header order and field name case. If no
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matching header was found, a :exc:`KeyError` is raised.
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.. method:: get_content_type()
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Return the message's content type. The returned string is coerced to
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lower case of the form :mimetype:`maintype/subtype`. If there was no
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:mailheader:`Content-Type` header in the message the default type as given
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by :meth:`get_default_type` will be returned. Since according to
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:rfc:`2045`, messages always have a default type, :meth:`get_content_type`
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will always return a value.
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:rfc:`2045` defines a message's default type to be :mimetype:`text/plain`
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unless it appears inside a :mimetype:`multipart/digest` container, in
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which case it would be :mimetype:`message/rfc822`. If the
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:mailheader:`Content-Type` header has an invalid type specification,
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:rfc:`2045` mandates that the default type be :mimetype:`text/plain`.
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.. method:: get_content_maintype()
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Return the message's main content type. This is the :mimetype:`maintype`
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part of the string returned by :meth:`get_content_type`.
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.. method:: get_content_subtype()
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Return the message's sub-content type. This is the :mimetype:`subtype`
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part of the string returned by :meth:`get_content_type`.
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.. method:: get_default_type()
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Return the default content type. Most messages have a default content
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type of :mimetype:`text/plain`, except for messages that are subparts of
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:mimetype:`multipart/digest` containers. Such subparts have a default
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content type of :mimetype:`message/rfc822`.
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.. method:: set_default_type(ctype)
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Set the default content type. *ctype* should either be
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:mimetype:`text/plain` or :mimetype:`message/rfc822`, although this is not
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enforced. The default content type is not stored in the
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:mailheader:`Content-Type` header.
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.. method:: get_params(failobj=None, header='content-type', unquote=True)
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Return the message's :mailheader:`Content-Type` parameters, as a list.
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The elements of the returned list are 2-tuples of key/value pairs, as
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split on the ``'='`` sign. The left hand side of the ``'='`` is the key,
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while the right hand side is the value. If there is no ``'='`` sign in
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the parameter the value is the empty string, otherwise the value is as
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described in :meth:`get_param` and is unquoted if optional *unquote* is
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``True`` (the default).
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Optional *failobj* is the object to return if there is no
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:mailheader:`Content-Type` header. Optional *header* is the header to
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search instead of :mailheader:`Content-Type`.
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.. method:: get_param(param, failobj=None, header='content-type', unquote=True)
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Return the value of the :mailheader:`Content-Type` header's parameter
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*param* as a string. If the message has no :mailheader:`Content-Type`
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header or if there is no such parameter, then *failobj* is returned
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(defaults to ``None``).
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Optional *header* if given, specifies the message header to use instead of
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:mailheader:`Content-Type`.
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Parameter keys are always compared case insensitively. The return value
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can either be a string, or a 3-tuple if the parameter was :rfc:`2231`
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encoded. When it's a 3-tuple, the elements of the value are of the form
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``(CHARSET, LANGUAGE, VALUE)``. Note that both ``CHARSET`` and
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``LANGUAGE`` can be ``None``, in which case you should consider ``VALUE``
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to be encoded in the ``us-ascii`` charset. You can usually ignore
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``LANGUAGE``.
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If your application doesn't care whether the parameter was encoded as in
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:rfc:`2231`, you can collapse the parameter value by calling
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:func:`email.utils.collapse_rfc2231_value`, passing in the return value
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from :meth:`get_param`. This will return a suitably decoded Unicode
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string when the value is a tuple, or the original string unquoted if it
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isn't. For example::
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rawparam = msg.get_param('foo')
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param = email.utils.collapse_rfc2231_value(rawparam)
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In any case, the parameter value (either the returned string, or the
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``VALUE`` item in the 3-tuple) is always unquoted, unless *unquote* is set
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to ``False``.
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.. method:: set_param(param, value, header='Content-Type', requote=True, charset=None, language='')
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Set a parameter in the :mailheader:`Content-Type` header. If the
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parameter already exists in the header, its value will be replaced with
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*value*. If the :mailheader:`Content-Type` header as not yet been defined
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for this message, it will be set to :mimetype:`text/plain` and the new
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parameter value will be appended as per :rfc:`2045`.
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Optional *header* specifies an alternative header to
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:mailheader:`Content-Type`, and all parameters will be quoted as necessary
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unless optional *requote* is ``False`` (the default is ``True``).
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If optional *charset* is specified, the parameter will be encoded
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according to :rfc:`2231`. Optional *language* specifies the RFC 2231
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language, defaulting to the empty string. Both *charset* and *language*
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should be strings.
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.. method:: del_param(param, header='content-type', requote=True)
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Remove the given parameter completely from the :mailheader:`Content-Type`
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header. The header will be re-written in place without the parameter or
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its value. All values will be quoted as necessary unless *requote* is
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``False`` (the default is ``True``). Optional *header* specifies an
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alternative to :mailheader:`Content-Type`.
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.. method:: set_type(type, header='Content-Type', requote=True)
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Set the main type and subtype for the :mailheader:`Content-Type`
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header. *type* must be a string in the form :mimetype:`maintype/subtype`,
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otherwise a :exc:`ValueError` is raised.
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This method replaces the :mailheader:`Content-Type` header, keeping all
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the parameters in place. If *requote* is ``False``, this leaves the
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existing header's quoting as is, otherwise the parameters will be quoted
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(the default).
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An alternative header can be specified in the *header* argument. When the
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:mailheader:`Content-Type` header is set a :mailheader:`MIME-Version`
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header is also added.
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.. method:: get_filename(failobj=None)
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Return the value of the ``filename`` parameter of the
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:mailheader:`Content-Disposition` header of the message. If the header
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does not have a ``filename`` parameter, this method falls back to looking
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for the ``name`` parameter on the :mailheader:`Content-Type` header. If
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neither is found, or the header is missing, then *failobj* is returned.
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The returned string will always be unquoted as per
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:func:`email.utils.unquote`.
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.. method:: get_boundary(failobj=None)
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Return the value of the ``boundary`` parameter of the
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:mailheader:`Content-Type` header of the message, or *failobj* if either
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the header is missing, or has no ``boundary`` parameter. The returned
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string will always be unquoted as per :func:`email.utils.unquote`.
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.. method:: set_boundary(boundary)
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Set the ``boundary`` parameter of the :mailheader:`Content-Type` header to
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*boundary*. :meth:`set_boundary` will always quote *boundary* if
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necessary. A :exc:`HeaderParseError` is raised if the message object has
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no :mailheader:`Content-Type` header.
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Note that using this method is subtly different than deleting the old
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|
:mailheader:`Content-Type` header and adding a new one with the new
|
|
boundary via :meth:`add_header`, because :meth:`set_boundary` preserves
|
|
the order of the :mailheader:`Content-Type` header in the list of
|
|
headers. However, it does *not* preserve any continuation lines which may
|
|
have been present in the original :mailheader:`Content-Type` header.
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|
|
.. method:: get_content_charset(failobj=None)
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|
|
Return the ``charset`` parameter of the :mailheader:`Content-Type` header,
|
|
coerced to lower case. If there is no :mailheader:`Content-Type` header, or if
|
|
that header has no ``charset`` parameter, *failobj* is returned.
|
|
|
|
Note that this method differs from :meth:`get_charset` which returns the
|
|
:class:`~email.charset.Charset` instance for the default encoding of the message body.
|
|
|
|
|
|
.. method:: get_charsets(failobj=None)
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|
|
|
Return a list containing the character set names in the message. If the
|
|
message is a :mimetype:`multipart`, then the list will contain one element
|
|
for each subpart in the payload, otherwise, it will be a list of length 1.
|
|
|
|
Each item in the list will be a string which is the value of the
|
|
``charset`` parameter in the :mailheader:`Content-Type` header for the
|
|
represented subpart. However, if the subpart has no
|
|
:mailheader:`Content-Type` header, no ``charset`` parameter, or is not of
|
|
the :mimetype:`text` main MIME type, then that item in the returned list
|
|
will be *failobj*.
|
|
|
|
|
|
.. method:: walk()
|
|
|
|
The :meth:`walk` method is an all-purpose generator which can be used to
|
|
iterate over all the parts and subparts of a message object tree, in
|
|
depth-first traversal order. You will typically use :meth:`walk` as the
|
|
iterator in a ``for`` loop; each iteration returns the next subpart.
|
|
|
|
Here's an example that prints the MIME type of every part of a multipart
|
|
message structure::
|
|
|
|
>>> for part in msg.walk():
|
|
... print(part.get_content_type())
|
|
multipart/report
|
|
text/plain
|
|
message/delivery-status
|
|
text/plain
|
|
text/plain
|
|
message/rfc822
|
|
|
|
:class:`Message` objects can also optionally contain two instance attributes,
|
|
which can be used when generating the plain text of a MIME message.
|
|
|
|
|
|
.. attribute:: preamble
|
|
|
|
The format of a MIME document allows for some text between the blank line
|
|
following the headers, and the first multipart boundary string. Normally,
|
|
this text is never visible in a MIME-aware mail reader because it falls
|
|
outside the standard MIME armor. However, when viewing the raw text of
|
|
the message, or when viewing the message in a non-MIME aware reader, this
|
|
text can become visible.
|
|
|
|
The *preamble* attribute contains this leading extra-armor text for MIME
|
|
documents. When the :class:`~email.parser.Parser` discovers some text
|
|
after the headers but before the first boundary string, it assigns this
|
|
text to the message's *preamble* attribute. When the
|
|
:class:`~email.generator.Generator` is writing out the plain text
|
|
representation of a MIME message, and it finds the
|
|
message has a *preamble* attribute, it will write this text in the area
|
|
between the headers and the first boundary. See :mod:`email.parser` and
|
|
:mod:`email.generator` for details.
|
|
|
|
Note that if the message object has no preamble, the *preamble* attribute
|
|
will be ``None``.
|
|
|
|
|
|
.. attribute:: epilogue
|
|
|
|
The *epilogue* attribute acts the same way as the *preamble* attribute,
|
|
except that it contains text that appears between the last boundary and
|
|
the end of the message.
|
|
|
|
You do not need to set the epilogue to the empty string in order for the
|
|
:class:`Generator` to print a newline at the end of the file.
|
|
|
|
|
|
.. attribute:: defects
|
|
|
|
The *defects* attribute contains a list of all the problems found when
|
|
parsing this message. See :mod:`email.errors` for a detailed description
|
|
of the possible parsing defects.
|