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1:mod:`email.encoders`: Encoders
2-------------------------------
3
4.. module:: email.encoders
5   :synopsis: Encoders for email message payloads.
6
7**Source code:** :source:`Lib/email/encoders.py`
8
9--------------
10
11This module is part of the legacy (``Compat32``) email API.  In the
12new API the functionality is provided by the *cte* parameter of
13the :meth:`~email.message.EmailMessage.set_content` method.
14
15The remaining text in this section is the original documentation of the module.
16
17When creating :class:`~email.message.Message` objects from scratch, you often
18need to encode the payloads for transport through compliant mail servers. This
19is especially true for :mimetype:`image/\*` and :mimetype:`text/\*` type messages
20containing binary data.
21
22The :mod:`email` package provides some convenient encodings in its
23:mod:`encoders` module.  These encoders are actually used by the
24:class:`~email.mime.audio.MIMEAudio` and :class:`~email.mime.image.MIMEImage`
25class constructors to provide default encodings.  All encoder functions take
26exactly one argument, the message object to encode.  They usually extract the
27payload, encode it, and reset the payload to this newly encoded value.  They
28should also set the :mailheader:`Content-Transfer-Encoding` header as appropriate.
29
30Note that these functions are not meaningful for a multipart message.  They
31must be applied to individual subparts instead, and will raise a
32:exc:`TypeError` if passed a message whose type is multipart.
33
34Here are the encoding functions provided:
35
36
37.. function:: encode_quopri(msg)
38
39   Encodes the payload into quoted-printable form and sets the
40   :mailheader:`Content-Transfer-Encoding` header to ``quoted-printable`` [#]_.
41   This is a good encoding to use when most of your payload is normal printable
42   data, but contains a few unprintable characters.
43
44
45.. function:: encode_base64(msg)
46
47   Encodes the payload into base64 form and sets the
48   :mailheader:`Content-Transfer-Encoding` header to ``base64``.  This is a good
49   encoding to use when most of your payload is unprintable data since it is a more
50   compact form than quoted-printable.  The drawback of base64 encoding is that it
51   renders the text non-human readable.
52
53
54.. function:: encode_7or8bit(msg)
55
56   This doesn't actually modify the message's payload, but it does set the
57   :mailheader:`Content-Transfer-Encoding` header to either ``7bit`` or ``8bit`` as
58   appropriate, based on the payload data.
59
60
61.. function:: encode_noop(msg)
62
63   This does nothing; it doesn't even set the
64   :mailheader:`Content-Transfer-Encoding` header.
65
66.. rubric:: Footnotes
67
68.. [#] Note that encoding with :meth:`encode_quopri` also encodes all tabs and space
69   characters in the data.
70
71