email.message: Representing an email message¶
Source code: Lib/email/message.py
New in version 3.6: [1]
The central class in the email package is the EmailMessage
class, imported from the email.message module. It is the base class for
the email object model. EmailMessage provides the core
functionality for setting and querying header fields, for accessing message
bodies, and for creating or modifying structured messages.
An email message consists of headers and a payload (which is also referred to as the content). Headers are RFC 5322 or RFC 6532 style field names and values, where the field name and value are separated by a colon. The colon is not part of either the field name or the field value. The payload may be a simple text message, or a binary object, or a structured sequence of sub-messages each with their own set of headers and their own payload. The latter type of payload is indicated by the message having a MIME type such as multipart/* or message/rfc822.
The conceptual model provided by an EmailMessage object is that of an
ordered dictionary of headers coupled with a payload that represents the
RFC 5322 body of the message, which might be a list of sub-EmailMessage
objects. In addition to the normal dictionary methods for accessing the header
names and values, there are methods for accessing specialized information from
the headers (for example the MIME content type), for operating on the payload,
for generating a serialized version of the message, and for recursively walking
over the object tree.
The EmailMessage dictionary-like interface is indexed by the header
names, which must be ASCII values. The values of the dictionary are strings
with some extra methods. Headers are stored and returned in case-preserving
form, but field names are matched case-insensitively. Unlike a real dict,
there is an ordering to the keys, and there can be duplicate keys. Additional
methods are provided for working with headers that have duplicate keys.
The payload is either a string or bytes object, in the case of simple message
objects, or a list of EmailMessage objects, for MIME container
documents such as multipart/* and message/rfc822
message objects.
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class
email.message.EmailMessage(policy=default)¶ If policy is specified use the rules it specifies to update and serialize the representation of the message. If policy is not set, use the
defaultpolicy, which follows the rules of the email RFCs except for line endings (instead of the RFC mandated\r\n, it uses the Python standard\nline endings). For more information see thepolicydocumentation.-
as_string(unixfrom=False, maxheaderlen=None, policy=None)¶ Return the entire message flattened as a string. When optional unixfrom is true, the envelope header is included in the returned string. unixfrom defaults to
False. For backward compatibility with the baseMessageclass maxheaderlen is accepted, but defaults toNone, which means that by default the line length is controlled by themax_line_lengthof the policy. The policy argument may be used to override the default policy obtained from the message instance. This can be used to control some of the formatting produced by the method, since the specified policy will be passed to theGenerator.Flattening the message may trigger changes to the
EmailMessageif defaults need to be filled in to complete the transformation to a string (for example, MIME boundaries may be generated or modified).Note that this method is provided as a convenience and may not be the most useful way to serialize messages in your application, especially if you are dealing with multiple messages. See
email.generator.Generatorfor a more flexible API for serializing messages. Note also that this method is restricted to producing messages serialized as “7 bit clean” whenutf8isFalse, which is the default.Changed in version 3.6: the default behavior when maxheaderlen is not specified was changed from defaulting to 0 to defaulting to the value of max_line_length from the policy.
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__str__()¶ Equivalent to as_string(policy=self.policy.clone(utf8=True). Allows
str(msg)to produce a string containing the serialized message in a readable format.Changed in version 3.4: the method was changed to use
utf8=True, thus producing an RFC 6531-like message representation, instead of being a direct alias foras_string().
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as_bytes(unixfrom=False, policy=None)¶ Return the entire message flattened as a bytes object. When optional unixfrom is true, the envelope header is included in the returned string. unixfrom defaults to
False. The policy argument may be used to override the default policy obtained from the message instance. This can be used to control some of the formatting produced by the method, since the specified policy will be passed to theBytesGenerator.Flattening the message may trigger changes to the
EmailMessageif defaults need to be filled in to complete the transformation to a string (for example, MIME boundaries may be generated or modified).Note that this method is provided as a convenience and may not be the most useful way to serialize messages in your application, especially if you are dealing with multiple messages. See
email.generator.BytesGeneratorfor a more flexible API for serializing messages.
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__bytes__()¶ Equivalent to
as_bytes(). Allowsbytes(msg)to produce a bytes object containing the serialized message.
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is_multipart()¶ Return
Trueif the message’s payload is a list of sub-EmailMessageobjects, otherwise returnFalse. Whenis_multipart()returnsFalse, the payload should be a string object (which might be a CTE encoded binary payload). Note thatis_multipart()returningTruedoes not necessarily mean that “msg.get_content_maintype() == ‘multipart’” will return theTrue. For example,is_multipartwill returnTruewhen theEmailMessageis of typemessage/rfc822.
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set_unixfrom(unixfrom)¶ Set the message’s envelope header to unixfrom, which should be a string. (See
mboxMessagefor a brief description of this header.)
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get_unixfrom()¶ Return the message’s envelope header. Defaults to
Noneif the envelope header was never set.
The following methods implement the mapping-like interface for accessing the message’s headers. Note that there are some semantic differences between these methods and a normal mapping (i.e. dictionary) interface. For example, in a dictionary there are no duplicate keys, but here there may be duplicate message headers. Also, in dictionaries there is no guaranteed order to the keys returned by
keys(), but in anEmailMessageobject, headers are always returned in the order they appeared in the original message, or in which they were added to the message later. Any header deleted and then re-added is always appended to the end of the header list.These semantic differences are intentional and are biased toward convenience in the most common use cases.
Note that in all cases, any envelope header present in the message is not included in the mapping interface.
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__len__()¶ Return the total number of headers, including duplicates.
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__contains__(name)¶ Return true if the message object has a field named name. Matching is done without regard to case and name does not include the trailing colon. Used for the
inoperator. For example:if 'message-id' in myMessage: print('Message-ID:', myMessage['message-id'])
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__getitem__(name)¶ Return the value of the named header field. name does not include the colon field separator. If the header is missing,
Noneis returned; aKeyErroris never raised.Note that if the named field appears more than once in the message’s headers, exactly which of those field values will be returned is undefined. Use the
get_all()method to get the values of all the extant headers named name.Using the standard (non-
compat32) policies, the returned value is an instance of a subclass ofemail.headerregistry.BaseHeader.
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__setitem__(name, val)¶ Add a header to the message with field name name and value val. The field is appended to the end of the message’s existing headers.
Note that this does not overwrite or delete any existing header with the same name. If you want to ensure that the new header is the only one present in the message with field name name, delete the field first, e.g.:
del msg['subject'] msg['subject'] = 'Python roolz!'
If the
policydefines certain headers to be unique (as the standard policies do), this method may raise aValueErrorwhen an attempt is made to assign a value to such a header when one already exists. This behavior is intentional for consistency’s sake, but do not depend on it as we may choose to make such assignments do an automatic deletion of the existing header in the future.
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__delitem__(name)¶ Delete all occurrences of the field with name name from the message’s headers. No exception is raised if the named field isn’t present in the headers.
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keys()¶ Return a list of all the message’s header field names.
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values()¶ Return a list of all the message’s field values.
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items()¶ Return a list of 2-tuples containing all the message’s field headers and values.
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get(name, failobj=None)¶ Return the value of the named header field. This is identical to
__getitem__()except that optional failobj is returned if the named header is missing (failobj defaults toNone).
Here are some additional useful header related methods:
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get_all(name, failobj=None)¶ Return a list of all the values for the field named name. If there are no such named headers in the message, failobj is returned (defaults to
None).
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add_header(_name, _value, **_params)¶ Extended header setting. This method is similar to
__setitem__()except that additional header parameters can be provided as keyword arguments. _name is the header field to add and _value is the primary value for the header.For each item in the keyword argument dictionary _params, the key is taken as the parameter name, with underscores converted to dashes (since dashes are illegal in Python identifiers). Normally, the parameter will be added as
key="value"unless the value isNone, in which case only the key will be added.If the value contains non-ASCII characters, the charset and language may be explicitly controlled by specifying the value as a three tuple in the format
(CHARSET, LANGUAGE, VALUE), whereCHARSETis a string naming the charset to be used to encode the value,LANGUAGEcan usually be set toNoneor the empty string (see RFC 2231 for other possibilities), andVALUEis the string value containing non-ASCII code points. If a three tuple is not passed and the value contains non-ASCII characters, it is automatically encoded in RFC 2231 format using aCHARSETofutf-8and aLANGUAGEofNone.Here is an example:
msg.add_header('Content-Disposition', 'attachment', filename='bud.gif')
This will add a header that looks like
Content-Disposition: attachment; filename="bud.gif"
An example of the extended interface with non-ASCII characters:
msg.add_header('Content-Disposition', 'attachment', filename=('iso-8859-1', '', 'Fußballer.ppt'))
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replace_header(_name, _value)¶ Replace a header. Replace the first header found in the message that matches _name, retaining header order and field name case of the original header. If no matching header is found, raise a
KeyError.
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get_content_type()¶ Return the message’s content type, coerced to lower case of the form maintype/subtype. If there is no Content-Type header in the message return the value returned by
get_default_type(). If the Content-Type header is invalid, returntext/plain.(According to RFC 2045, messages always have a default type,
get_content_type()will always return a value. RFC 2045 defines a message’s default type to be text/plain unless it appears inside a multipart/digest container, in which case it would be message/rfc822. If the Content-Type header has an invalid type specification, RFC 2045 mandates that the default type be text/plain.)
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get_content_maintype()¶ Return the message’s main content type. This is the maintype part of the string returned by
get_content_type().
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get_content_subtype()¶ Return the message’s sub-content type. This is the subtype part of the string returned by
get_content_type().
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get_default_type()¶ Return the default content type. Most messages have a default content type of text/plain, except for messages that are subparts of multipart/digest containers. Such subparts have a default content type of message/rfc822.
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set_default_type(ctype)¶ Set the default content type. ctype should either be text/plain or message/rfc822, although this is not enforced. The default content type is not stored in the Content-Type header, so it only affects the return value of the
get_content_typemethods when no Content-Type header is present in the message.
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set_param(param, value, header='Content-Type', requote=True, charset=None, language='', replace=False)¶ Set a parameter in the Content-Type header. If the parameter already exists in the header, replace its value with value. When header is
Content-Type(the default) and the header does not yet exist in the message, add it, set its value to text/plain, and append the new parameter value. Optional header specifies an alternative header to Content-Type.If the value contains non-ASCII characters, the charset and language may be explicitly specified using the optional charset and language parameters. Optional language specifies the RFC 2231 language, defaulting to the empty string. Both charset and language should be strings. The default is to use the
utf8charset andNonefor the language.If replace is
False(the default) the header is moved to the end of the list of headers. If replace isTrue, the header will be updated in place.Use of the requote parameter with
EmailMessageobjects is deprecated.Note that existing parameter values of headers may be accessed through the
paramsattribute of the header value (for example,msg['Content-Type'].params['charset'].Changed in version 3.4:
replacekeyword was added.
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del_param(param, header='content-type', requote=True)¶ Remove the given parameter completely from the Content-Type header. The header will be re-written in place without the parameter or its value. Optional header specifies an alternative to Content-Type.
Use of the requote parameter with
EmailMessageobjects is deprecated.
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get_filename(failobj=None)¶ Return the value of the
filenameparameter of the Content-Disposition header of the message. If the header does not have afilenameparameter, this method falls back to looking for thenameparameter on the Content-Type header. If neither is found, or the header is missing, then failobj is returned. The returned string will always be unquoted as peremail.utils.unquote().
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get_boundary(failobj=None)¶ Return the value of the
boundaryparameter of the Content-Type header of the message, or failobj if either the header is missing, or has noboundaryparameter. The returned string will always be unquoted as peremail.utils.unquote().
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set_boundary(boundary)¶ Set the
boundaryparameter of the Content-Type header to boundary.set_boundary()will always quote boundary if necessary. AHeaderParseErroris raised if the message object has no Content-Type header.Note that using this method is subtly different from deleting the old Content-Type header and adding a new one with the new boundary via
add_header(), becauseset_boundary()preserves the order of the Content-Type header in the list of headers.
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get_content_charset(failobj=None)¶ Return the
charsetparameter of the Content-Type header, coerced to lower case. If there is no Content-Type header, or if that header has nocharsetparameter, failobj is returned.
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get_charsets(failobj=None)¶ Return a list containing the character set names in the message. If the message is a 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
charsetparameter in the Content-Type header for the represented subpart. If the subpart has no Content-Type header, nocharsetparameter, or is not of the text main MIME type, then that item in the returned list will be failobj.
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is_attachment()¶ Return
Trueif there is a Content-Disposition header and its (case insensitive) value isattachment,Falseotherwise.Changed in version 3.4.2: is_attachment is now a method instead of a property, for consistency with
is_multipart().
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get_content_disposition()¶ Return the lowercased value (without parameters) of the message’s Content-Disposition header if it has one, or
None. The possible values for this method are inline, attachment orNoneif the message follows RFC 2183.New in version 3.5.
The following methods relate to interrogating and manipulating the content (payload) of the message.
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walk()¶ The
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 usewalk()as the iterator in aforloop; 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 text/plain
walkiterates over the subparts of any part whereis_multipart()returnsTrue, even thoughmsg.get_content_maintype() == 'multipart'may returnFalse. We can see this in our example by making use of the_structuredebug helper function:>>> for part in msg.walk(): ... print(part.get_content_maintype() == 'multipart', ... part.is_multipart()) True True False False False True False False False False False True False False >>> _structure(msg) multipart/report text/plain message/delivery-status text/plain text/plain message/rfc822 text/plain
Here the
messageparts are notmultiparts, but they do contain subparts.is_multipart()returnsTrueandwalkdescends into the subparts.
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get_body(preferencelist=('related', 'html', 'plain'))¶ Return the MIME part that is the best candidate to be the “body” of the message.
preferencelist must be a sequence of strings from the set
related,html, andplain, and indicates the order of preference for the content type of the part returned.Start looking for candidate matches with the object on which the
get_bodymethod is called.If
relatedis not included in preferencelist, consider the root part (or subpart of the root part) of any related encountered as a candidate if the (sub-)part matches a preference.When encountering a
multipart/related, check thestartparameter and if a part with a matching Content-ID is found, consider only it when looking for candidate matches. Otherwise consider only the first (default root) part of themultipart/related.If a part has a Content-Disposition header, only consider the part a candidate match if the value of the header is
inline.If none of the candidates matches any of the preferences in preferencelist, return
None.Notes: (1) For most applications the only preferencelist combinations that really make sense are
('plain',),('html', 'plain'), and the default('related', 'html', 'plain'). (2) Because matching starts with the object on whichget_bodyis called, callingget_bodyon amultipart/relatedwill return the object itself unless preferencelist has a non-default value. (3) Messages (or message parts) that do not specify a Content-Type or whose Content-Type header is invalid will be treated as if they are of typetext/plain, which may occasionally causeget_bodyto return unexpected results.
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iter_attachments()¶ Return an iterator over all of the immediate sub-parts of the message that are not candidate “body” parts. That is, skip the first occurrence of each of
text/plain,text/html,multipart/related, ormultipart/alternative(unless they are explicitly marked as attachments via Content-Disposition: attachment), and return all remaining parts. When applied directly to amultipart/related, return an iterator over the all the related parts except the root part (ie: the part pointed to by thestartparameter, or the first part if there is nostartparameter or thestartparameter doesn’t match the Content-ID of any of the parts). When applied directly to amultipart/alternativeor a non-multipart, return an empty iterator.
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iter_parts()¶ Return an iterator over all of the immediate sub-parts of the message, which will be empty for a non-
multipart. (See alsowalk().)
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get_content(*args, content_manager=None, **kw)¶ Call the
get_content()method of the content_manager, passing self as the message object, and passing along any other arguments or keywords as additional arguments. If content_manager is not specified, use thecontent_managerspecified by the currentpolicy.
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set_content(*args, content_manager=None, **kw)¶ Call the
set_content()method of the content_manager, passing self as the message object, and passing along any other arguments or keywords as additional arguments. If content_manager is not specified, use thecontent_managerspecified by the currentpolicy.
Convert a non-
multipartmessage into amultipart/relatedmessage, moving any existing Content- headers and payload into a (new) first part of themultipart. If boundary is specified, use it as the boundary string in the multipart, otherwise leave the boundary to be automatically created when it is needed (for example, when the message is serialized).
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make_alternative(boundary=None)¶ Convert a non-
multipartor amultipart/relatedinto amultipart/alternative, moving any existing Content- headers and payload into a (new) first part of themultipart. If boundary is specified, use it as the boundary string in the multipart, otherwise leave the boundary to be automatically created when it is needed (for example, when the message is serialized).
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make_mixed(boundary=None)¶ Convert a non-
multipart, amultipart/related, or amultipart-alternativeinto amultipart/mixed, moving any existing Content- headers and payload into a (new) first part of themultipart. If boundary is specified, use it as the boundary string in the multipart, otherwise leave the boundary to be automatically created when it is needed (for example, when the message is serialized).
If the message is a
multipart/related, create a new message object, pass all of the arguments to itsset_content()method, andattach()it to themultipart. If the message is a non-multipart, callmake_related()and then proceed as above. If the message is any other type ofmultipart, raise aTypeError. If content_manager is not specified, use thecontent_managerspecified by the currentpolicy. If the added part has no Content-Disposition header, add one with the valueinline.
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add_alternative(*args, content_manager=None, **kw)¶ If the message is a
multipart/alternative, create a new message object, pass all of the arguments to itsset_content()method, andattach()it to themultipart. If the message is a non-multipartormultipart/related, callmake_alternative()and then proceed as above. If the message is any other type ofmultipart, raise aTypeError. If content_manager is not specified, use thecontent_managerspecified by the currentpolicy.
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add_attachment(*args, content_manager=None, **kw)¶ If the message is a
multipart/mixed, create a new message object, pass all of the arguments to itsset_content()method, andattach()it to themultipart. If the message is a non-multipart,multipart/related, ormultipart/alternative, callmake_mixed()and then proceed as above. If content_manager is not specified, use thecontent_managerspecified by the currentpolicy. If the added part has no Content-Disposition header, add one with the valueattachment. This method can be used both for explicit attachments (Content-Disposition: attachment andinlineattachments (Content-Disposition: inline), by passing appropriate options to thecontent_manager.
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clear()¶ Remove the payload and all of the headers.
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clear_content()¶ Remove the payload and all of the
Content-headers, leaving all other headers intact and in their original order.
EmailMessageobjects have the following instance attributes:-
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
Parserdiscovers some text after the headers but before the first boundary string, it assigns this text to the message’s preamble attribute. When theGeneratoris 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. Seeemail.parserandemail.generatorfor details.Note that if the message object has no preamble, the preamble attribute will be
None.
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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. As with the
preamble, if there is no epilog text this attribute will beNone.
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defects¶ The defects attribute contains a list of all the problems found when parsing this message. See
email.errorsfor a detailed description of the possible parsing defects.
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class
email.message.MIMEPart(policy=default)¶ This class represents a subpart of a MIME message. It is identical to
EmailMessage, except that no MIME-Version headers are added whenset_content()is called, since sub-parts do not need their own MIME-Version headers.
Footnotes
| [1] | Originally added in 3.4 as a provisional module. Docs for legacy message class moved to email.message.Message: Representing an email message using the compat32 API. |
