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
Unix-From header, also known as the envelope header or the
From_ header. The payload is either a string in the case of
simple message objects, a list of Message objects for
multipart MIME documents, or a single Message instance for
message/rfc822 type objects.
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:
From_header) to unixfrom, which should be a string.
Noneif the Unix-From header was never set.
None(i.e. never before set), then after this method is called, the payload will be the argument payload.
If the object's payload was already a list (i.e. is_multipart() returns 1), then payload is appended to the end of the existing payload list.
For any other type of existing payload, add_payload() will transform the new payload into a list consisting of the old payload and payload, but only if the document is already a MIME multipart document. This condition is satisfied if the message's Content-Type: header's main type is either multipart, or there is no Content-Type: header. In any other situation, MultipartConversionError is raised.
With optional i, get_payload() will return the i-th element of the payload, counting from zero, if is_multipart() returns 1. 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 scalar (i.e. is_multipart() returns 0) 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). If the message is
a multipart and the decode flag is true, then
The following methods implement a mapping-like interface for accessing the message object'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, there is an explicit order. These semantic differences are intentional and are biased toward maximal convenience.
Note that in all cases, any optional Unix-From header the message may have is not included in the mapping interface.
if 'message-id' in myMessage: print 'Message-ID:', myMessage['message-id']
Noneis 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.
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, first use __delitem__() to delete all named fields, e.g.:
del msg['subject'] msg['subject'] = 'Python roolz!'
Here are some additional useful methods:
If there are no such named headers in the message, failobj is
returned (defaults to
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"
If there is no Content-Type: header in the message,
failobj is returned (defaults to
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:.
Optional header if given, specifies the message header to use instead of Content-Type:.
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.
filenameparameter of the Content-Disposition: header of the message, or failobj if either the header is missing, or has no
filenameparameter. The returned string will always be unquoted as per Utils.unquote().
boundaryparameter of the Content-Type: header of the message, or failobj if either the header is missing, or has no
boundaryparameter. The returned string will always be unquoted as per Utils.unquote().
boundaryparameter of the Content-Type: header to boundary. set_boundary() will always quote boundary so you should not quote it yourself. A 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.
for ... inloop; each iteration returns the next subpart.
Here's an example that prints the MIME type of every part of a message object tree:
>>> for part in msg.walk(): >>> print part.get_type('text/plain') 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.
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.
Note that if the message object has no preamble, the
preamble attribute will be
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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