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The central class in the email package is the Message
class; it is the base class for the email object model. Message provides the core functionality for setting and querying header
fields, and for accessing message bodies.
Conceptually, a Message object consists of headers and payloads.
Headers are RFC
2822 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.
Headers are stored and returned in case-preserving form but 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 in the case of simple message objects or a list of Message objects for MIME container documents (e.g. multipart/*
and message/rfc822).
Message objects provide a mapping style interface for accessing the
message headers, and an explicit interface for accessing both the headers and the payload. It
provides convenience methods for generating a flat text representation of the message object
tree, for accessing commonly used header parameters, and for recursively walking over the
object tree.
Here are the methods of the Message class:
-
- The constructor takes no arguments.
-
- Return the entire message flatten as a string. When optional unixfrom is
True,
the envelope header is included in the returned string. unixfrom defaults to False.
Note that this method is provided as a convenience and may not always format the
message the way you want. For more flexibility, instantiate a Generator
instance and use its flatten() method directly. For example:
from cStringIO import StringIO
from email.Generator import Generator
fp = StringIO()
g = Generator(fp, mangle_from_=False, maxheaderlen=60)
g.flatten(msg)
text = fp.getvalue()
- Equivalent to as_string(unixfrom=True).
-
- 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.
-
- Set the message's envelope header to unixfrom, which should be a string.
-
- Return the message's envelope header. Defaults to
None if the envelope
header was never set.
-
- 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.
-
| get_payload( |
[i[, decode]]) |
- Return a reference 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
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 header is missing, or if the payload
has bogus base64 data, the payload is returned as-is (undecoded). If the message is a
multipart and the decode flag is True, then None is
returned. The default for decode is False.
-
| set_payload( |
payload[, charset]) |
- 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.
Changed in version 2.2.2: charset argument added.
-
- Set the character set of the payload to charset, which can either be a Charset instance (see email.Charset), a string naming a character set,
or
None. If it is a string, it will be converted to a Charset
instance. If charset is None, the charset parameter
will be removed from the header. Anything
else will generate a TypeError.
The message will be assumed to be of type text/* encoded
with charset.input_charset. It will be converted to charset.output_charset
and encoded properly, if needed, when generating the plain text representation of the
message. MIME headers (, , )
will be added as needed.
New in version 2.2.2.
-
- Return the Charset instance associated with the message's
payload. New in version 2.2.2.
The following methods implement a mapping-like interface for accessing the message's RFC 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.
-
- Return the total number of headers, including duplicates.
-
- 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']
-
- 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.
-
- 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!'
-
- 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.
-
- Return true if the message contains a header field named name, otherwise
return false.
-
- Return a list of all the message's header field names.
-
- Return a list of all the message's field values.
-
- Return a list of 2-tuples containing all the message's field headers and values.
-
- 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]) |
- 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.
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"
-
| 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.
New in version 2.2.2.
-
- Return the message's content type. The returned string is coerced to lower case of the
form maintype/subtype. If there was no header in the message the default type as given by
get_default_type() will be returned. Since 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
header has an invalid type specification, RFC 2045 mandates that the default type
be text/plain.
New in version 2.2.2.
-
- Return the message's main content type. This is the maintype
part of the string returned by get_content_type().
New in version 2.2.2.
-
- Return the message's sub-content type. This is the subtype
part of the string returned by get_content_type().
New in version 2.2.2.
-
- 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.
New in version 2.2.2.
-
- 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
header.
New in version 2.2.2.
-
| get_params( |
[failobj[, header[,
unquote]]]) |
- Return the message's 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 header. Optional header is the header
to search instead of .
Changed in version 2.2.2: unquote argument added.
-
| get_param( |
param[, failobj[, header[,
unquote]]]) |
- Return the value of the header's parameter
param as a string. If the message has no
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 .
Parameter keys are always compared case insensitively. The return value can either be a
string, or a 3-tuple if the parameter was RFC 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.
Your application should be prepared to deal with 3-tuple return values, and can convert
the parameter to a Unicode string like so:
param = msg.get_param('foo')
if isinstance(param, tuple):
param = unicode(param[2], param[0] or 'us-ascii')
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.
Changed in version 2.2.2: unquote argument added,
and 3-tuple return value possible.
-
| set_param( |
param, value[, header[, requote[,
charset[, language]]]]) |
-
Set a parameter in the header. If the
parameter already exists in the header, its value will be replaced with value.
If the 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 RFC 2045.
Optional header specifies an alternative header to ,
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
RFC 2231.
Optional language specifies the RFC 2231 language, defaulting to the empty
string. Both charset and language should be strings.
New in version 2.2.2.
-
| del_param( |
param[, header[, requote]]) |
- Remove the given parameter completely from the
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 .
New in version 2.2.2.
-
| set_type( |
type[, header][, requote]) |
- Set the main type and subtype for the
header. type must be a string in the form maintype/subtype,
otherwise a ValueError is raised.
This method replaces the 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 header is set a
header is also added.
New in version 2.2.2.
-
- Return the value of the
filename parameter of the
header of the message, or failobj if either the header is missing, or has no filename
parameter. The returned string will always be unquoted as per Utils.unquote().
-
- Return the value of the
boundary parameter of the
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 Utils.unquote().
-
- Set the
boundary parameter of the
header to boundary. set_boundary() will always quote boundary
if necessary. A HeaderParseError is raised if the message
object has no header.
Note that using this method is subtly different than deleting the old header and adding a new one with the new boundary
via add_header(), because set_boundary()
preserves the order of the header in the
list of headers. However, it does not preserve any continuation lines which may
have been present in the original header.
-
| get_content_charset( |
[failobj]) |
- Return the
charset parameter of the
header, coerced to lower case. If there is no
header, or if that header has no charset parameter, failobj is
returned.
Note that this method differs from get_charset() which returns
the Charset instance for the default encoding of the message body.
New in version 2.2.2.
-
- 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 header for the represented
subpart. However, if the subpart has no
header, no charset parameter, or is not of the text
main MIME type, then that item in the returned list will be failobj.
-
- 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:
>>> for part in msg.walk():
>>> print part.get_content_type()
multipart/report
text/plain
message/delivery-status
text/plain
text/plain
message/rfc822
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 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 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.
One note: when generating the flat text for a multipart
message that has no epilogue (using the standard Generator
class), no newline is added after the closing boundary line. If the message object has an epilogue
and its value does not start with a newline, a newline is printed after the closing
boundary. This seems a little clumsy, but it makes the most practical sense. The upshot is
that if you want to ensure that a newline get printed after your closing multipart boundary, set the epilogue to the empty
string.
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