19.1.13. "email.encoders": Encoders
***********************************

**Source code:** Lib/email/encoders.py

======================================================================

This module is part of the legacy ("Compat32") email API.  In the new
API the functionality is provided by the *cte* parameter of the
"set_content()" method.

本段落中的剩余文本是该模块的原始文档。

When creating "Message" objects from scratch, you often need to encode
the payloads for transport through compliant mail servers. This is
especially true for *image/** and *text/** type messages containing
binary data.

The "email" package provides some convenient encodings in its
"encoders" module.  These encoders are actually used by the
"MIMEAudio" and "MIMEImage" class constructors to provide default
encodings.  All encoder functions take exactly one argument, the
message object to encode.  They usually extract the payload, encode
it, and reset the payload to this newly encoded value.  They should
also set the *Content-Transfer-Encoding* header as appropriate.

请注意，这些函数对于多段消息没有意义。 它们必须应用到各个单独的段上面
，而不是整体。如果直接传递一个多段类型的消息，会产生一个 "TypeError"
错误。

下面是提供的编码函数：

email.encoders.encode_quopri(msg)

   将有效数据编码为quoted-printable形式，并将:mailheader:*Content-
   Transfer-Encoding`标头设置为``quoted-printable`* [1]. 。当大多数实
   际的数据是普通的可打印数据但包含少量不可打印的字符时，这是一个很好
   的编码。

email.encoders.encode_base64(msg)

   Encodes the payload into base64 form and sets the *Content-
   Transfer-Encoding* header to "base64".  This is a good encoding to
   use when most of your payload is unprintable data since it is a
   more compact form than quoted-printable.  The drawback of base64
   encoding is that it renders the text non-human readable.

email.encoders.encode_7or8bit(msg)

   This doesn't actually modify the message's payload, but it does set
   the *Content-Transfer-Encoding* header to either "7bit" or "8bit"
   as appropriate, based on the payload data.

email.encoders.encode_noop(msg)

   这样什么都不会做；它甚至不会设置 *Content-Transfer-Encoding* 标头。

-[ 脚注 ]-

[1] Note that encoding with "encode_quopri()" also encodes all
    tabs and space characters in the data.
