email.message
The Message
class is very similar to the ~email.message.EmailMessage
class, without the methods added by that class, and with the default behavior of certain other methods being slightly different. We also document here some methods that, while supported by the ~email.message.EmailMessage
class, are not recommended unless you are dealing with legacy code.
The philosophy and structure of the two classes is otherwise the same.
This document describes the behavior under the default (for Message
) policy ~email.policy.Compat32
. If you are going to use another policy, you should be using the ~email.message.EmailMessage
class instead.
An email message consists of headers and a payload. Headers must be 5322
style 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 a Message
object is that of an ordered dictionary of headers with additional methods for accessing both specialized information from the headers, for accessing the payload, for generating a serialized version of the message, and for recursively walking over the object tree. Note that duplicate headers are supported but special methods must be used to access them.
The Message
pseudo-dictionary is indexed by the header names, which must be ASCII values. The values of the dictionary are strings that are supposed to contain only ASCII characters; there is some special handling for non-ASCII input, but it doesn't always produce the correct results. Headers are stored and returned in case-preserving form, but field names are matched case-insensitively. There may also be a single envelope header, also known as the Unix-From header or the From_
header. The payload is either a string or bytes, in the case of simple message objects, or a list of Message
objects, for MIME container documents (e.g. multipart/\*
and message/rfc822
).
Here are the methods of the Message
class:
If policy is specified (it must be an instance of a ~email.policy
class) use the rules it specifies to update and serialize the representation of the message. If policy is not set, use the compat32
<email.policy.Compat32>
policy, which maintains backward compatibility with the Python 3.2 version of the email package. For more information see the ~email.policy
documentation.
3.3 The policy keyword argument was added.
as_string(unixfrom=False, maxheaderlen=0, 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 reasons, maxheaderlen defaults to 0
, so if you want a different value you must override it explicitly (the value specified for max_line_length in the policy will be ignored by this method). 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 the Generator
.
Flattening the message may trigger changes to the Message
if 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 always format the message the way you want. For example, by default it does not do the mangling of lines that begin with From
that is required by the Unix mbox format. For more flexibility, instantiate a ~email.generator.Generator
instance and use its ~email.generator.Generator.flatten
method directly. For example:
from io import StringIO
from email.generator import Generator
fp = StringIO()
g = Generator(fp, mangle_from_=True, maxheaderlen=60)
g.flatten(msg)
text = fp.getvalue()
If the message object contains binary data that is not encoded according to RFC standards, the non-compliant data will be replaced by unicode "unknown character" code points. (See also .as_bytes
and ~email.generator.BytesGenerator
.)
3.4 the policy keyword argument was added.
__str__()
Equivalent to .as_string()
. Allows str(msg)
to produce a string containing the formatted message.
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 the BytesGenerator
.
Flattening the message may trigger changes to the Message
if 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 always format the message the way you want. For example, by default it does not do the mangling of lines that begin with From
that is required by the Unix mbox format. For more flexibility, instantiate a ~email.generator.BytesGenerator
instance and use its ~email.generator.BytesGenerator.flatten
method directly. For example:
from io import BytesIO
from email.generator import BytesGenerator
fp = BytesIO()
g = BytesGenerator(fp, mangle_from_=True, maxheaderlen=60)
g.flatten(msg)
text = fp.getvalue()
3.4
__bytes__()
Equivalent to .as_bytes()
. Allows bytes(msg)
to produce a bytes object containing the formatted message.
3.4
is_multipart()
Return True
if the message's payload is a list of sub-Message
objects, otherwise return False
. When is_multipart
returns False
, the payload should be a string object (which might be a CTE encoded binary payload). (Note that is_multipart
returning True
does not necessarily mean that "msg.get_content_maintype() == 'multipart'" will return the True
. For example, is_multipart
will return True
when the Message
is of type message/rfc822
.)
set_unixfrom(unixfrom)
Set the message's envelope header to unixfrom, which should be a string.
get_unixfrom()
Return the message's envelope header. Defaults to None
if the envelope header was never set.
attach(payload)
Add the given payload to the current payload, which must be None
or a list of Message
objects before the call. After the call, the payload will always be a list of Message
objects. If you want to set the payload to a scalar object (e.g. a string), use set_payload
instead.
This is a legacy method. On the ~email.emailmessage.EmailMessage
class its functionality is replaced by ~email.message.EmailMessage.set_content
and the related make
and add
methods.
get_payload(i=None, decode=False)
Return the current payload, which will be a list of Message
objects when is_multipart
is True
, or a string when is_multipart
is False
. If the payload is a list and you mutate the list object, you modify the message's payload in place.
With optional argument i, get_payload
will return the i-th element of the payload, counting from zero, if is_multipart
is True
. An IndexError
will be raised if i is less than 0 or greater than or equal to the number of items in the payload. If the payload is a string (i.e. is_multipart
is False
) and i is given, a TypeError
is raised.
Optional decode is a flag indicating whether the payload should be decoded or not, according to the Content-Transfer-Encoding
header. When True
and the message is not a multipart, the payload will be decoded if this header's value is quoted-printable
or base64
. If some other encoding is used, or Content-Transfer-Encoding
header is missing, the payload is returned as-is (undecoded). In all cases the returned value is binary data. If the message is a multipart and the decode flag is True
, then None
is returned. If the payload is base64 and it was not perfectly formed (missing padding, characters outside the base64 alphabet), then an appropriate defect will be added to the message's defect property (~email.errors.InvalidBase64PaddingDefect
or ~email.errors.InvalidBase64CharactersDefect
, respectively).
When decode is False
(the default) the body is returned as a string without decoding the Content-Transfer-Encoding
. However, for a Content-Transfer-Encoding
of 8bit, an attempt is made to decode the original bytes using the charset
specified by the Content-Type
header, using the replace
error handler. If no charset
is specified, or if the charset
given is not recognized by the email package, the body is decoded using the default ASCII charset.
This is a legacy method. On the ~email.emailmessage.EmailMessage
class its functionality is replaced by ~email.message.EmailMessage.get_content
and ~email.message.EmailMessage.iter_parts
.
set_payload(payload, charset=None)
Set the entire message object's payload to payload. It is the client's responsibility to ensure the payload invariants. Optional charset sets the message's default character set; see set_charset
for details.
This is a legacy method. On the ~email.emailmessage.EmailMessage
class its functionality is replaced by ~email.message.EmailMessage.set_content
.
set_charset(charset)
Set the character set of the payload to charset, which can either be a ~email.charset.Charset
instance (see email.charset
), a string naming a character set, or None
. If it is a string, it will be converted to a ~email.charset.Charset
instance. If charset is None
, the charset
parameter will be removed from the Content-Type
header (the message will not be otherwise modified). Anything else will generate a TypeError
.
If there is no existing MIME-Version
header one will be added. If there is no existing Content-Type
header, one will be added with a value of text/plain
. Whether the Content-Type
header already exists or not, its charset
parameter will be set to charset.output_charset. If charset.input_charset and charset.output_charset differ, the payload will be re-encoded to the output_charset. If there is no existing Content-Transfer-Encoding
header, then the payload will be transfer-encoded, if needed, using the specified ~email.charset.Charset
, and a header with the appropriate value will be added. If a Content-Transfer-Encoding
header already exists, the payload is assumed to already be correctly encoded using that Content-Transfer-Encoding
and is not modified.
This is a legacy method. On the ~email.emailmessage.EmailMessage
class its functionality is replaced by the charset parameter of the email.emailmessage.EmailMessage.set_content
method.
get_charset()
Return the ~email.charset.Charset
instance associated with the message's payload.
This is a legacy method. On the ~email.emailmessage.EmailMessage
class it always returns None
.
The following methods implement a mapping-like interface for accessing the message's 2822
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 a Message
object, headers are always returned in the order they appeared in the original message, or were added to the message later. Any header deleted and then re-added are always appended to the end of the header list.
These semantic differences are intentional and are biased toward maximal convenience.
Note that in all cases, any envelope header present in the message is not included in the mapping interface.
In a model generated from bytes, any header values that (in contravention of the RFCs) contain non-ASCII bytes will, when retrieved through this interface, be represented as ~email.header.Header
objects with a charset of unknown-8bit
.
__len__()
Return the total number of headers, including duplicates.
__contains__(name)
Return True
if the message object has a field named name. Matching is done case-insensitively and name should not include the trailing colon. Used for the in
operator, e.g.:
if 'message-id' in myMessage:
print('Message-ID:', myMessage['message-id'])
__getitem__(name)
Return the value of the named header field. name should not include the colon field separator. If the header is missing, None
is returned; a KeyError
is 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 named headers.
__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 fields.
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!'
__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.
keys()
Return a list of all the message's header field names.
values()
Return a list of all the message's field values.
items()
Return a list of 2-tuples containing all the message's field headers and values.
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 (defaults to None
).
Here are some additional useful methods:
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
).
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 is None
, in which case only the key will be added. If the value contains non-ASCII characters, it can be specified as a three tuple in the format (CHARSET, LANGUAGE, VALUE)
, where CHARSET
is a string naming the charset to be used to encode the value, LANGUAGE
can usually be set to None
or the empty string (see 2231
for other possibilities), and VALUE
is 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 2231
format using a CHARSET
of utf-8
and a LANGUAGE
of None
.
Here's 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 with non-ASCII characters:
msg.add_header('Content-Disposition', 'attachment',
filename=('iso-8859-1', '', 'Fußballer.ppt'))
Which produces :
Content-Disposition: attachment; filename*="iso-8859-1''Fu%DFballer.ppt"
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. If no matching header was found, a KeyError
is raised.
get_content_type()
Return the message's content type. The returned string is coerced to lower case of the form maintype/subtype
. If there was no Content-Type
header in the message the default type as given by get_default_type
will be returned. Since according to 2045
, messages always have a default type, get_content_type
will always return a value.
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, 2045
mandates that the default type be text/plain
.
get_content_maintype()
Return the message's main content type. This is the maintype
part of the string returned by get_content_type
.
get_content_subtype()
Return the message's sub-content type. This is the subtype
part of the string returned by get_content_type
.
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
.
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.
get_params(failobj=None, header='content-type', unquote=True)
Return the message's Content-Type
parameters, as a list. The elements of the returned list are 2-tuples of key/value pairs, as split on the '='
sign. The left hand side of the '='
is the key, while the right hand side is the value. If there is no '='
sign in the parameter the value is the empty string, otherwise the value is as described in get_param
and is unquoted if optional unquote is True
(the default).
Optional failobj is the object to return if there is no Content-Type
header. Optional header is the header to search instead of Content-Type
.
This is a legacy method. On the ~email.emailmessage.EmailMessage
class its functionality is replaced by the params property of the individual header objects returned by the header access methods.
get_param(param, failobj=None, header='content-type', unquote=True)
Return the value of the Content-Type
header's parameter param as a string. If the message has no Content-Type
header or if there is no such parameter, then failobj is returned (defaults to None
).
Optional header if given, specifies the message header to use instead of Content-Type
.
Parameter keys are always compared case insensitively. The return value can either be a string, or a 3-tuple if the parameter was 2231
encoded. When it's a 3-tuple, the elements of the value are of the form (CHARSET, LANGUAGE, VALUE)
. Note that both CHARSET
and LANGUAGE
can be None
, in which case you should consider VALUE
to be encoded in the us-ascii
charset. You can usually ignore LANGUAGE
.
If your application doesn't care whether the parameter was encoded as in 2231
, you can collapse the parameter value by calling email.utils.collapse_rfc2231_value
, passing in the return value from get_param
. This will return a suitably decoded Unicode string when the value is a tuple, or the original string unquoted if it isn't. For example:
rawparam = msg.get_param('foo')
param = email.utils.collapse_rfc2231_value(rawparam)
In any case, the parameter value (either the returned string, or the VALUE
item in the 3-tuple) is always unquoted, unless unquote is set to False
.
This is a legacy method. On the ~email.emailmessage.EmailMessage
class its functionality is replaced by the params property of the individual header objects returned by the header access methods.
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, its value will be replaced with value. If the Content-Type
header as not yet been defined for this message, it will be set to text/plain
and the new parameter value will be appended as per 2045
.
Optional header specifies an alternative header to Content-Type
, and all parameters will be quoted as necessary unless optional requote is False
(the default is True
).
If optional charset is specified, the parameter will be encoded according to 2231
. Optional language specifies the RFC 2231 language, defaulting to the empty string. Both charset and language should be strings.
If replace is False
(the default) the header is moved to the end of the list of headers. If replace is True
, the header will be updated in place.
3.4 replace
keyword was added.
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. All values will be quoted as necessary unless requote is False
(the default is True
). Optional header specifies an alternative to Content-Type
.
set_type(type, header='Content-Type', requote=True)
Set the main type and subtype for the Content-Type
header. type must be a string in the form maintype/subtype
, otherwise a ValueError
is raised.
This method replaces the Content-Type
header, keeping all the parameters in place. If requote is False
, this leaves the existing header's quoting as is, otherwise the parameters will be quoted (the default).
An alternative header can be specified in the header argument. When the Content-Type
header is set a MIME-Version
header is also added.
This is a legacy method. On the ~email.emailmessage.EmailMessage
class its functionality is replaced by the make_
and add_
methods.
get_filename(failobj=None)
Return the value of the filename
parameter of the Content-Disposition
header of the message. If the header does not have a filename
parameter, this method falls back to looking for the name
parameter 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 per email.utils.unquote
.
get_boundary(failobj=None)
Return the value of the boundary
parameter of the Content-Type
header of the message, or failobj if either the header is missing, or has no boundary
parameter. The returned string will always be unquoted as per email.utils.unquote
.
set_boundary(boundary)
Set the boundary
parameter of the Content-Type
header to boundary. set_boundary
will always quote boundary if necessary. A ~email.errors.HeaderParseError
is raised if the message object has no Content-Type
header.
Note that using this method is subtly different than deleting the old Content-Type
header and adding a new one with the new boundary via add_header
, because set_boundary
preserves the order of the Content-Type
header in the list of headers. However, it does not preserve any continuation lines which may have been present in the original Content-Type
header.
get_content_charset(failobj=None)
Return the charset
parameter of the Content-Type
header, coerced to lower case. If there is no Content-Type
header, or if that header has no charset
parameter, failobj is returned.
Note that this method differs from get_charset
which returns the ~email.charset.Charset
instance for the default encoding of the message body.
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 charset
parameter in the Content-Type
header for the represented subpart. However, if the subpart has no Content-Type
header, no charset
parameter, or is not of the text
main MIME type, then that item in the returned list will be failobj.
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 or None
if the message follows 2183
.
3.5
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 use 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:
import email from email import message_from_binary_file from os.path import join, dirname lib_dir = dirname(dirname(email.__file__)) file_path = join(lib_dir, 'test/test_email/data/msg_16.txt') with open(file_path, 'rb') as f: msg = message_from_binary_file(f) from email.iterators import _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
walk
iterates over the subparts of any part where is_multipart
returns True
, even though msg.get_content_maintype() == 'multipart'
may return False
. We can see this in our example by making use of the _structure
debug 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 message
parts are not multiparts
, but they do contain subparts. is_multipart()
returns True
and walk
descends into the subparts.
Message
objects can also optionally contain two instance attributes, which can be used when generating the plain text of a MIME message.
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 ~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 ~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 email.parser
and email.generator
for details.
Note that if the message object has no preamble, the preamble attribute will be None
.
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 ~email.generator.Generator
to print a newline at the end of the file.
defects
The defects attribute contains a list of all the problems found when parsing this message. See email.errors
for a detailed description of the possible parsing defects.