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
15This module is deprecated in Python 3.  The functions provided here
16should not be called explicitly since the :class:`~email.mime.text.MIMEText`
17class sets the content type and CTE header using the *_subtype* and *_charset*
18values passed during the instaniation of that class.
19
20The remaining text in this section is the original documentation of the module.
21
22When creating :class:`~email.message.Message` objects from scratch, you often
23need to encode the payloads for transport through compliant mail servers. This
24is especially true for :mimetype:`image/\*` and :mimetype:`text/\*` type messages
25containing binary data.
26
27The :mod:`email` package provides some convenient encoders in its
28:mod:`encoders` module.  These encoders are actually used by the
29:class:`~email.mime.audio.MIMEAudio` and :class:`~email.mime.image.MIMEImage`
30class constructors to provide default encodings.  All encoder functions take
31exactly one argument, the message object to encode.  They usually extract the
32payload, encode it, and reset the payload to this newly encoded value.  They
33should also set the :mailheader:`Content-Transfer-Encoding` header as appropriate.
34
35Note that these functions are not meaningful for a multipart message.  They
36must be applied to individual subparts instead, and will raise a
37:exc:`TypeError` if passed a message whose type is multipart.
38
39Here are the encoding functions provided:
40
41
42.. function:: encode_quopri(msg)
43
44   Encodes the payload into quoted-printable form and sets the
45   :mailheader:`Content-Transfer-Encoding` header to ``quoted-printable`` [#]_.
46   This is a good encoding to use when most of your payload is normal printable
47   data, but contains a few unprintable characters.
48
49
50.. function:: encode_base64(msg)
51
52   Encodes the payload into base64 form and sets the
53   :mailheader:`Content-Transfer-Encoding` header to ``base64``.  This is a good
54   encoding to use when most of your payload is unprintable data since it is a more
55   compact form than quoted-printable.  The drawback of base64 encoding is that it
56   renders the text non-human readable.
57
58
59.. function:: encode_7or8bit(msg)
60
61   This doesn't actually modify the message's payload, but it does set the
62   :mailheader:`Content-Transfer-Encoding` header to either ``7bit`` or ``8bit`` as
63   appropriate, based on the payload data.
64
65
66.. function:: encode_noop(msg)
67
68   This does nothing; it doesn't even set the
69   :mailheader:`Content-Transfer-Encoding` header.
70
71.. rubric:: Footnotes
72
73.. [#] Note that encoding with :meth:`encode_quopri` also encodes all tabs and space
74   characters in the data.
75
76