email: Generating MIME documents
One of the most common tasks is to generate the flat text of the email message
represented by a message object structure. You will need to do this if you want
to send your message via the smtplib module or the nntplib module,
or print the message on the console. Taking a message object structure and
producing a flat text document is the job of the Generator class.
Again, as with the email.parser module, you aren’t limited to the
functionality of the bundled generator; you could write one from scratch
yourself. However the bundled generator knows how to generate most email in a
standards-compliant way, should handle MIME and non-MIME email messages just
fine, and is designed so that the transformation from flat text, to a message
structure via the Parser class, and back to flat text, is idempotent
(the input is identical to the output).
Here are the public methods of the Generator class, imported from the
email.generator module:
-
class email.generator.Generator(outfp[, mangle_from_[, maxheaderlen]])
The constructor for the Generator class takes a file-like object called
outfp for an argument. outfp must support the write() method and be
usable as the output file in a Python extended print statement.
Optional mangle_from_ is a flag that, when True, puts a > character in
front of any line in the body that starts exactly as From, i.e. From
followed by a space at the beginning of the line. This is the only guaranteed
portable way to avoid having such lines be mistaken for a Unix mailbox format
envelope header separator (see WHY THE CONTENT-LENGTH FORMAT IS BAD for details). mangle_from_
defaults to True, but you might want to set this to False if you are not
writing Unix mailbox format files.
Optional maxheaderlen specifies the longest length for a non-continued header.
When a header line is longer than maxheaderlen (in characters, with tabs
expanded to 8 spaces), the header will be split as defined in the
email.header.Header class. Set to zero to disable header wrapping. The
default is 78, as recommended (but not required) by RFC 2822.
The other public Generator methods are:
-
flatten(msg[, unixfrom])
Print the textual representation of the message object structure rooted at
msg to the output file specified when the Generator instance
was created. Subparts are visited depth-first and the resulting text will
be properly MIME encoded.
Optional unixfrom is a flag that forces the printing of the envelope
header delimiter before the first RFC 2822 header of the root message
object. If the root object has no envelope header, a standard one is
crafted. By default, this is set to False to inhibit the printing of
the envelope delimiter.
Note that for subparts, no envelope header is ever printed.
New in version 2.2.2.
-
clone(fp)
Return an independent clone of this Generator instance with the
exact same options.
New in version 2.2.2.
-
write(s)
- Write the string s to the underlying file object, i.e. outfp passed to
Generator‘s constructor. This provides just enough file-like API
for Generator instances to be used in extended print statements.
As a convenience, see the methods Message.as_string() and
str(aMessage), a.k.a. Message.__str__(), which simplify the generation
of a formatted string representation of a message object. For more detail, see
email.message.
The email.generator module also provides a derived class, called
DecodedGenerator which is like the Generator base class,
except that non-text parts are substituted with a format string
representing the part.
-
class email.generator.DecodedGenerator(outfp[, mangle_from_[, maxheaderlen[, fmt]]])
This class, derived from Generator walks through all the subparts of a
message. If the subpart is of main type text, then it prints the
decoded payload of the subpart. Optional _mangle_from_ and maxheaderlen are
as with the Generator base class.
If the subpart is not of main type text, optional fmt is a format
string that is used instead of the message payload. fmt is expanded with the
following keywords, %(keyword)s format:
- type – Full MIME type of the non-text part
- maintype – Main MIME type of the non-text part
- subtype – Sub-MIME type of the non-text part
- filename – Filename of the non-text part
- description – Description associated with the non-text part
- encoding – Content transfer encoding of the non-text part
The default value for fmt is None, meaning
[Non-text (%(type)s) part of message omitted, filename %(filename)s]
New in version 2.2.2.
Changed in version 2.5: The previously deprecated method __call__() was removed.