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
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) 1. On the other hand, using the Generator on a
Message constructed by program may result in changes to the
Message object as defaults are filled in.
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 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
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:
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.
Return an independent clone of this
Generator instance with the exact same options.
New in version 2.2.2.
As a convenience, see the methods
Message.__str__(), which simplify the generation of a formatted string representation of a message object. For more detail, see
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,
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
[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.
This statement assumes that you use the appropriate setting for the
unixfrom argument, and that you set maxheaderlen=0 (which will preserve whatever the input line lengths were). It is also not strictly true, since in many cases runs of whitespace in headers are collapsed into single blanks. The latter is a bug that will eventually be fixed.
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