1 :mod:`email`: Representing an email message
2 -------------------------------------------
4 .. module:: email.message
5 :synopsis: The base class representing email messages.
8 The central class in the :mod:`email` package is the :class:`Message` class,
9 imported from the :mod:`email.message` module. It is the base class for the
10 :mod:`email` object model. :class:`Message` provides the core functionality for
11 setting and querying header fields, and for accessing message bodies.
13 Conceptually, a :class:`Message` object consists of *headers* and *payloads*.
14 Headers are :rfc:`2822` style field names and values where the field name and
15 value are separated by a colon. The colon is not part of either the field name
18 Headers are stored and returned in case-preserving form but are matched
19 case-insensitively. There may also be a single envelope header, also known as
20 the *Unix-From* header or the ``From_`` header. The payload is either a string
21 in the case of simple message objects or a list of :class:`Message` objects for
22 MIME container documents (e.g. :mimetype:`multipart/\*` and
23 :mimetype:`message/rfc822`).
25 :class:`Message` objects provide a mapping style interface for accessing the
26 message headers, and an explicit interface for accessing both the headers and
27 the payload. It provides convenience methods for generating a flat text
28 representation of the message object tree, for accessing commonly used header
29 parameters, and for recursively walking over the object tree.
31 Here are the methods of the :class:`Message` class:
36 The constructor takes no arguments.
39 .. method:: as_string([unixfrom])
41 Return the entire message flattened as a string. When optional *unixfrom*
42 is ``True``, the envelope header is included in the returned string.
43 *unixfrom* defaults to ``False``.
45 Note that this method is provided as a convenience and may not always
46 format the message the way you want. For example, by default it mangles
47 lines that begin with ``From``. For more flexibility, instantiate a
48 :class:`Generator` instance and use its :meth:`flatten` method directly.
51 from cStringIO import StringIO
52 from email.generator import Generator
54 g = Generator(fp, mangle_from_=False, maxheaderlen=60)
61 Equivalent to ``as_string(unixfrom=True)``.
64 .. method:: is_multipart()
66 Return ``True`` if the message's payload is a list of sub-\
67 :class:`Message` objects, otherwise return ``False``. When
68 :meth:`is_multipart` returns False, the payload should be a string object.
71 .. method:: set_unixfrom(unixfrom)
73 Set the message's envelope header to *unixfrom*, which should be a string.
76 .. method:: get_unixfrom()
78 Return the message's envelope header. Defaults to ``None`` if the
79 envelope header was never set.
82 .. method:: attach(payload)
84 Add the given *payload* to the current payload, which must be ``None`` or
85 a list of :class:`Message` objects before the call. After the call, the
86 payload will always be a list of :class:`Message` objects. If you want to
87 set the payload to a scalar object (e.g. a string), use
88 :meth:`set_payload` instead.
91 .. method:: get_payload([i[, decode]])
93 Return a reference the current payload, which will be a list of
94 :class:`Message` objects when :meth:`is_multipart` is ``True``, or a
95 string when :meth:`is_multipart` is ``False``. If the payload is a list
96 and you mutate the list object, you modify the message's payload in place.
98 With optional argument *i*, :meth:`get_payload` will return the *i*-th
99 element of the payload, counting from zero, if :meth:`is_multipart` is
100 ``True``. An :exc:`IndexError` will be raised if *i* is less than 0 or
101 greater than or equal to the number of items in the payload. If the
102 payload is a string (i.e. :meth:`is_multipart` is ``False``) and *i* is
103 given, a :exc:`TypeError` is raised.
105 Optional *decode* is a flag indicating whether the payload should be
106 decoded or not, according to the :mailheader:`Content-Transfer-Encoding`
107 header. When ``True`` and the message is not a multipart, the payload will
108 be decoded if this header's value is ``quoted-printable`` or ``base64``.
109 If some other encoding is used, or :mailheader:`Content-Transfer-Encoding`
110 header is missing, or if the payload has bogus base64 data, the payload is
111 returned as-is (undecoded). If the message is a multipart and the
112 *decode* flag is ``True``, then ``None`` is returned. The default for
113 *decode* is ``False``.
116 .. method:: set_payload(payload[, charset])
118 Set the entire message object's payload to *payload*. It is the client's
119 responsibility to ensure the payload invariants. Optional *charset* sets
120 the message's default character set; see :meth:`set_charset` for details.
122 .. versionchanged:: 2.2.2
123 *charset* argument added.
126 .. method:: set_charset(charset)
128 Set the character set of the payload to *charset*, which can either be a
129 :class:`Charset` instance (see :mod:`email.charset`), a string naming a
130 character set, or ``None``. If it is a string, it will be converted to a
131 :class:`Charset` instance. If *charset* is ``None``, the ``charset``
132 parameter will be removed from the :mailheader:`Content-Type`
133 header. Anything else will generate a :exc:`TypeError`.
135 The message will be assumed to be of type :mimetype:`text/\*` encoded with
136 *charset.input_charset*. It will be converted to *charset.output_charset*
137 and encoded properly, if needed, when generating the plain text
138 representation of the message. MIME headers (:mailheader:`MIME-Version`,
139 :mailheader:`Content-Type`, :mailheader:`Content-Transfer-Encoding`) will
142 .. versionadded:: 2.2.2
145 .. method:: get_charset()
147 Return the :class:`Charset` instance associated with the message's
150 .. versionadded:: 2.2.2
152 The following methods implement a mapping-like interface for accessing the
153 message's :rfc:`2822` headers. Note that there are some semantic differences
154 between these methods and a normal mapping (i.e. dictionary) interface. For
155 example, in a dictionary there are no duplicate keys, but here there may be
156 duplicate message headers. Also, in dictionaries there is no guaranteed
157 order to the keys returned by :meth:`keys`, but in a :class:`Message` object,
158 headers are always returned in the order they appeared in the original
159 message, or were added to the message later. Any header deleted and then
160 re-added are always appended to the end of the header list.
162 These semantic differences are intentional and are biased toward maximal
165 Note that in all cases, any envelope header present in the message is not
166 included in the mapping interface.
169 .. method:: __len__()
171 Return the total number of headers, including duplicates.
174 .. method:: __contains__(name)
176 Return true if the message object has a field named *name*. Matching is
177 done case-insensitively and *name* should not include the trailing colon.
178 Used for the ``in`` operator, e.g.::
180 if 'message-id' in myMessage:
181 print 'Message-ID:', myMessage['message-id']
184 .. method:: __getitem__(name)
186 Return the value of the named header field. *name* should not include the
187 colon field separator. If the header is missing, ``None`` is returned; a
188 :exc:`KeyError` is never raised.
190 Note that if the named field appears more than once in the message's
191 headers, exactly which of those field values will be returned is
192 undefined. Use the :meth:`get_all` method to get the values of all the
193 extant named headers.
196 .. method:: __setitem__(name, val)
198 Add a header to the message with field name *name* and value *val*. The
199 field is appended to the end of the message's existing fields.
201 Note that this does *not* overwrite or delete any existing header with the same
202 name. If you want to ensure that the new header is the only one present in the
203 message with field name *name*, delete the field first, e.g.::
206 msg['subject'] = 'Python roolz!'
209 .. method:: __delitem__(name)
211 Delete all occurrences of the field with name *name* from the message's
212 headers. No exception is raised if the named field isn't present in the headers.
215 .. method:: has_key(name)
217 Return true if the message contains a header field named *name*, otherwise
223 Return a list of all the message's header field names.
228 Return a list of all the message's field values.
233 Return a list of 2-tuples containing all the message's field headers and
237 .. method:: get(name[, failobj])
239 Return the value of the named header field. This is identical to
240 :meth:`__getitem__` except that optional *failobj* is returned if the
241 named header is missing (defaults to ``None``).
243 Here are some additional useful methods:
246 .. method:: get_all(name[, failobj])
248 Return a list of all the values for the field named *name*. If there are
249 no such named headers in the message, *failobj* is returned (defaults to
253 .. method:: add_header(_name, _value, **_params)
255 Extended header setting. This method is similar to :meth:`__setitem__`
256 except that additional header parameters can be provided as keyword
257 arguments. *_name* is the header field to add and *_value* is the
258 *primary* value for the header.
260 For each item in the keyword argument dictionary *_params*, the key is
261 taken as the parameter name, with underscores converted to dashes (since
262 dashes are illegal in Python identifiers). Normally, the parameter will
263 be added as ``key="value"`` unless the value is ``None``, in which case
264 only the key will be added.
268 msg.add_header('Content-Disposition', 'attachment', filename='bud.gif')
270 This will add a header that looks like ::
272 Content-Disposition: attachment; filename="bud.gif"
275 .. method:: replace_header(_name, _value)
277 Replace a header. Replace the first header found in the message that
278 matches *_name*, retaining header order and field name case. If no
279 matching header was found, a :exc:`KeyError` is raised.
281 .. versionadded:: 2.2.2
284 .. method:: get_content_type()
286 Return the message's content type. The returned string is coerced to
287 lower case of the form :mimetype:`maintype/subtype`. If there was no
288 :mailheader:`Content-Type` header in the message the default type as given
289 by :meth:`get_default_type` will be returned. Since according to
290 :rfc:`2045`, messages always have a default type, :meth:`get_content_type`
291 will always return a value.
293 :rfc:`2045` defines a message's default type to be :mimetype:`text/plain`
294 unless it appears inside a :mimetype:`multipart/digest` container, in
295 which case it would be :mimetype:`message/rfc822`. If the
296 :mailheader:`Content-Type` header has an invalid type specification,
297 :rfc:`2045` mandates that the default type be :mimetype:`text/plain`.
299 .. versionadded:: 2.2.2
302 .. method:: get_content_maintype()
304 Return the message's main content type. This is the :mimetype:`maintype`
305 part of the string returned by :meth:`get_content_type`.
307 .. versionadded:: 2.2.2
310 .. method:: get_content_subtype()
312 Return the message's sub-content type. This is the :mimetype:`subtype`
313 part of the string returned by :meth:`get_content_type`.
315 .. versionadded:: 2.2.2
318 .. method:: get_default_type()
320 Return the default content type. Most messages have a default content
321 type of :mimetype:`text/plain`, except for messages that are subparts of
322 :mimetype:`multipart/digest` containers. Such subparts have a default
323 content type of :mimetype:`message/rfc822`.
325 .. versionadded:: 2.2.2
328 .. method:: set_default_type(ctype)
330 Set the default content type. *ctype* should either be
331 :mimetype:`text/plain` or :mimetype:`message/rfc822`, although this is not
332 enforced. The default content type is not stored in the
333 :mailheader:`Content-Type` header.
335 .. versionadded:: 2.2.2
338 .. method:: get_params([failobj[, header[, unquote]]])
340 Return the message's :mailheader:`Content-Type` parameters, as a list.
341 The elements of the returned list are 2-tuples of key/value pairs, as
342 split on the ``'='`` sign. The left hand side of the ``'='`` is the key,
343 while the right hand side is the value. If there is no ``'='`` sign in
344 the parameter the value is the empty string, otherwise the value is as
345 described in :meth:`get_param` and is unquoted if optional *unquote* is
346 ``True`` (the default).
348 Optional *failobj* is the object to return if there is no
349 :mailheader:`Content-Type` header. Optional *header* is the header to
350 search instead of :mailheader:`Content-Type`.
352 .. versionchanged:: 2.2.2
353 *unquote* argument added.
356 .. method:: get_param(param[, failobj[, header[, unquote]]])
358 Return the value of the :mailheader:`Content-Type` header's parameter
359 *param* as a string. If the message has no :mailheader:`Content-Type`
360 header or if there is no such parameter, then *failobj* is returned
361 (defaults to ``None``).
363 Optional *header* if given, specifies the message header to use instead of
364 :mailheader:`Content-Type`.
366 Parameter keys are always compared case insensitively. The return value
367 can either be a string, or a 3-tuple if the parameter was :rfc:`2231`
368 encoded. When it's a 3-tuple, the elements of the value are of the form
369 ``(CHARSET, LANGUAGE, VALUE)``. Note that both ``CHARSET`` and
370 ``LANGUAGE`` can be ``None``, in which case you should consider ``VALUE``
371 to be encoded in the ``us-ascii`` charset. You can usually ignore
374 If your application doesn't care whether the parameter was encoded as in
375 :rfc:`2231`, you can collapse the parameter value by calling
376 :func:`email.Utils.collapse_rfc2231_value`, passing in the return value
377 from :meth:`get_param`. This will return a suitably decoded Unicode
378 string whn the value is a tuple, or the original string unquoted if it
381 rawparam = msg.get_param('foo')
382 param = email.Utils.collapse_rfc2231_value(rawparam)
384 In any case, the parameter value (either the returned string, or the
385 ``VALUE`` item in the 3-tuple) is always unquoted, unless *unquote* is set
388 .. versionchanged:: 2.2.2
389 *unquote* argument added, and 3-tuple return value possible.
392 .. method:: set_param(param, value[, header[, requote[, charset[, language]]]])
394 Set a parameter in the :mailheader:`Content-Type` header. If the
395 parameter already exists in the header, its value will be replaced with
396 *value*. If the :mailheader:`Content-Type` header as not yet been defined
397 for this message, it will be set to :mimetype:`text/plain` and the new
398 parameter value will be appended as per :rfc:`2045`.
400 Optional *header* specifies an alternative header to
401 :mailheader:`Content-Type`, and all parameters will be quoted as necessary
402 unless optional *requote* is ``False`` (the default is ``True``).
404 If optional *charset* is specified, the parameter will be encoded
405 according to :rfc:`2231`. Optional *language* specifies the RFC 2231
406 language, defaulting to the empty string. Both *charset* and *language*
409 .. versionadded:: 2.2.2
412 .. method:: del_param(param[, header[, requote]])
414 Remove the given parameter completely from the :mailheader:`Content-Type`
415 header. The header will be re-written in place without the parameter or
416 its value. All values will be quoted as necessary unless *requote* is
417 ``False`` (the default is ``True``). Optional *header* specifies an
418 alternative to :mailheader:`Content-Type`.
420 .. versionadded:: 2.2.2
423 .. method:: set_type(type[, header][, requote])
425 Set the main type and subtype for the :mailheader:`Content-Type`
426 header. *type* must be a string in the form :mimetype:`maintype/subtype`,
427 otherwise a :exc:`ValueError` is raised.
429 This method replaces the :mailheader:`Content-Type` header, keeping all
430 the parameters in place. If *requote* is ``False``, this leaves the
431 existing header's quoting as is, otherwise the parameters will be quoted
434 An alternative header can be specified in the *header* argument. When the
435 :mailheader:`Content-Type` header is set a :mailheader:`MIME-Version`
436 header is also added.
438 .. versionadded:: 2.2.2
441 .. method:: get_filename([failobj])
443 Return the value of the ``filename`` parameter of the
444 :mailheader:`Content-Disposition` header of the message. If the header
445 does not have a ``filename`` parameter, this method falls back to looking
446 for the ``name`` parameter. If neither is found, or the header is
447 missing, then *failobj* is returned. The returned string will always be
448 unquoted as per :meth:`Utils.unquote`.
451 .. method:: get_boundary([failobj])
453 Return the value of the ``boundary`` parameter of the
454 :mailheader:`Content-Type` header of the message, or *failobj* if either
455 the header is missing, or has no ``boundary`` parameter. The returned
456 string will always be unquoted as per :meth:`Utils.unquote`.
459 .. method:: set_boundary(boundary)
461 Set the ``boundary`` parameter of the :mailheader:`Content-Type` header to
462 *boundary*. :meth:`set_boundary` will always quote *boundary* if
463 necessary. A :exc:`HeaderParseError` is raised if the message object has
464 no :mailheader:`Content-Type` header.
466 Note that using this method is subtly different than deleting the old
467 :mailheader:`Content-Type` header and adding a new one with the new
468 boundary via :meth:`add_header`, because :meth:`set_boundary` preserves
469 the order of the :mailheader:`Content-Type` header in the list of
470 headers. However, it does *not* preserve any continuation lines which may
471 have been present in the original :mailheader:`Content-Type` header.
474 .. method:: get_content_charset([failobj])
476 Return the ``charset`` parameter of the :mailheader:`Content-Type` header,
477 coerced to lower case. If there is no :mailheader:`Content-Type` header, or if
478 that header has no ``charset`` parameter, *failobj* is returned.
480 Note that this method differs from :meth:`get_charset` which returns the
481 :class:`Charset` instance for the default encoding of the message body.
483 .. versionadded:: 2.2.2
486 .. method:: get_charsets([failobj])
488 Return a list containing the character set names in the message. If the
489 message is a :mimetype:`multipart`, then the list will contain one element
490 for each subpart in the payload, otherwise, it will be a list of length 1.
492 Each item in the list will be a string which is the value of the
493 ``charset`` parameter in the :mailheader:`Content-Type` header for the
494 represented subpart. However, if the subpart has no
495 :mailheader:`Content-Type` header, no ``charset`` parameter, or is not of
496 the :mimetype:`text` main MIME type, then that item in the returned list
502 The :meth:`walk` method is an all-purpose generator which can be used to
503 iterate over all the parts and subparts of a message object tree, in
504 depth-first traversal order. You will typically use :meth:`walk` as the
505 iterator in a ``for`` loop; each iteration returns the next subpart.
507 Here's an example that prints the MIME type of every part of a multipart
510 >>> for part in msg.walk():
511 ... print part.get_content_type()
514 message/delivery-status
519 .. versionchanged:: 2.5
520 The previously deprecated methods :meth:`get_type`, :meth:`get_main_type`, and
521 :meth:`get_subtype` were removed.
523 :class:`Message` objects can also optionally contain two instance attributes,
524 which can be used when generating the plain text of a MIME message.
527 .. attribute:: preamble
529 The format of a MIME document allows for some text between the blank line
530 following the headers, and the first multipart boundary string. Normally,
531 this text is never visible in a MIME-aware mail reader because it falls
532 outside the standard MIME armor. However, when viewing the raw text of
533 the message, or when viewing the message in a non-MIME aware reader, this
534 text can become visible.
536 The *preamble* attribute contains this leading extra-armor text for MIME
537 documents. When the :class:`Parser` discovers some text after the headers
538 but before the first boundary string, it assigns this text to the
539 message's *preamble* attribute. When the :class:`Generator` is writing
540 out the plain text representation of a MIME message, and it finds the
541 message has a *preamble* attribute, it will write this text in the area
542 between the headers and the first boundary. See :mod:`email.parser` and
543 :mod:`email.generator` for details.
545 Note that if the message object has no preamble, the *preamble* attribute
549 .. attribute:: epilogue
551 The *epilogue* attribute acts the same way as the *preamble* attribute,
552 except that it contains text that appears between the last boundary and
553 the end of the message.
555 .. versionchanged:: 2.5
556 You do not need to set the epilogue to the empty string in order for the
557 :class:`Generator` to print a newline at the end of the file.
560 .. attribute:: defects
562 The *defects* attribute contains a list of all the problems found when
563 parsing this message. See :mod:`email.errors` for a detailed description
564 of the possible parsing defects.
566 .. versionadded:: 2.4