email.charset
：表示字符集
¶
此模块提供类
Charset
for representing character sets and character set conversions in email messages, as well as a character set registry and several convenience methods for manipulating this registry. Instances of
Charset
are used in several other modules within the
email
包。
导入此类从
email.charset
模块。
New in version 2.2.2.
email.charset.
Charset
(
[
input_charset
]
)
¶
将字符集映射到其 Email 特性。
This class provides information about the requirements imposed on email for a specific character set. It also provides convenience routines for converting between character sets, given the availability of the applicable codecs. Given a character set, it will do its best to provide information on how to use that character set in an email message in an RFC-compliant way.
Certain character sets must be encoded with quoted-printable or base64 when used in email headers or bodies. Certain character sets must be converted outright, and are not allowed in email.
可选
input_charset
is as described below; it is always coerced to lower case. After being alias normalized it is also used as a lookup into the registry of character sets to find out the header encoding, body encoding, and output conversion codec to be used for the character set. For example, if
input_charset
is
iso-8859-1
, then headers and bodies will be encoded using quoted-printable and no output conversion codec is necessary. If
input_charset
is
euc-jp
, then headers will be encoded with base64, bodies will not be encoded, but output text will be converted from the
euc-jp
character set to the
iso-2022-jp
字符集。
Charset
实例拥有下列数据属性：
input_charset
¶
The initial character set specified. Common aliases are converted to their
official
email names (e.g.
latin_1
被转换成
iso-8859-1
)。默认为 7 位
us-ascii
.
header_encoding
¶
If the character set must be encoded before it can be used in an email header, this attribute will be set to
Charset.QP
(for quoted-printable),
Charset.BASE64
(for base64 encoding), or
Charset.SHORTEST
for the shortest of QP or BASE64 encoding. Otherwise, it will be
None
.
body_encoding
¶
如同
header_encoding
, but describes the encoding for the mail message’s body, which indeed may be different than the header encoding.
Charset.SHORTEST
is not allowed for
body_encoding
.
output_charset
¶
Some character sets must be converted before they can be used in email headers or bodies. If the
input_charset
is one of them, this attribute will contain the name of the character set output will be converted to. Otherwise, it will be
None
.
input_codec
¶
The name of the Python codec used to convert the
input_charset
to Unicode. If no conversion codec is necessary, this attribute will be
None
.
output_codec
¶
The name of the Python codec used to convert Unicode to the output_charset . If no conversion codec is necessary, this attribute will have the same value as the input_codec .
Charset
实例还拥有下列方法：
get_body_encoding
(
)
¶
Return the content transfer encoding used for body encoding.
This is either the string
quoted-printable
or
base64
depending on the encoding used, or it is a function, in which case you should call the function with a single argument, the Message object being encoded. The function should then set the
Content-Transfer-Encoding
header itself to whatever is appropriate.
返回字符串
quoted-printable
if
body_encoding
is
QP
, returns the string
base64
if
body_encoding
is
BASE64
，及返回字符串
7bit
否则。
convert
(
s
)
¶
Convert the string s 从 input_codec 到 output_codec .
to_splittable
(
s
)
¶
Convert a possibly multibyte string to a safely splittable format. s is the string to split.
Uses the input_codec to try and convert the string to Unicode, so it can be safely split on character boundaries (even for multibyte characters).
Returns the string as-is if it isn’t known how to convert s to Unicode with the input_charset .
Characters that could not be converted to Unicode will be replaced with the Unicode replacement character
'U+FFFD'
.
from_splittable
(
ustr
[
,
to_output
]
)
¶
Convert a splittable string back into an encoded string. ustr is a Unicode string to “unsplit”.
This method uses the proper codec to try and convert the string from Unicode back into an encoded format. Return the string as-is if it is not Unicode, or if it could not be converted from Unicode.
Characters that could not be converted from Unicode will be replaced with an appropriate character (usually
'?'
).
若
to_output
is
True
(the default), uses
output_codec
to convert to an encoded format. If
to_output
is
False
, it uses
input_codec
.
get_output_charset
(
)
¶
返回输出字符集。
这是
output_charset
attribute if that is not
None
, otherwise it is
input_charset
.
encoded_header_len
(
)
¶
Return the length of the encoded header string, properly calculating for quoted-printable or base64 encoding.
header_encode
(
s
[
,
convert
]
)
¶
Header-encode the string s .
若
convert
is
True
, the string will be converted from the input charset to the output charset automatically. This is not useful for multibyte character sets, which have line length issues (multibyte characters must be split on a character, not a byte boundary); use the higher-level
Header
class to deal with these issues (see
email.header
).
convert
默认为
False
.
The type of encoding (base64 or quoted-printable) will be based on the header_encoding 属性。
body_encode
(
s
[
,
convert
]
)
¶
Body-encode the string s .
若
convert
is
True
(the default), the string will be converted from the input charset to output charset automatically. Unlike
header_encode()
, there are no issues with byte boundaries and multibyte charsets in email bodies, so this is usually pretty safe.
The type of encoding (base64 or quoted-printable) will be based on the body_encoding 属性。
The
Charset
class also provides a number of methods to support standard operations and built-in functions.
__str__
(
)
¶
返回
input_charset
as a string coerced to lower case.
__repr__()
是别名化的
__str__()
.
The
email.charset
module also provides the following functions for adding new entries to the global character set, alias, and codec registries:
email.charset.
add_charset
(
charset
[
,
header_enc
[
,
body_enc
[
,
output_charset
]
]
]
)
¶
Add character properties to the global registry.
charset is the input character set, and must be the canonical name of a character set.
可选
header_enc
and
body_enc
是
Charset.QP
for quoted-printable,
Charset.BASE64
for base64 encoding,
Charset.SHORTEST
for the shortest of quoted-printable or base64 encoding, or
None
for no encoding.
SHORTEST
is only valid for
header_enc
。默认为
None
for no encoding.
可选
output_charset
is the character set that the output should be in. Conversions will proceed from input charset, to Unicode, to the output charset when the method
Charset.convert()
is called. The default is to output in the same character set as the input.
Both
input_charset
and
output_charset
must have Unicode codec entries in the module’s character set-to-codec mapping; use
add_codec()
to add codecs the module does not know about. See the
codecs
module’s documentation for more information.
The global character set registry is kept in the module global dictionary
CHARSETS
.
email.charset.
add_alias
(
alias
,
canonical
)
¶
Add a character set alias.
alias
is the alias name, e.g.
latin-1
.
canonical
is the character set’s canonical name, e.g.
iso-8859-1
.
The global charset alias registry is kept in the module global dictionary
ALIASES
.
email.charset.
add_codec
(
charset
,
codecname
)
¶
Add a codec that map characters in the given character set to and from Unicode.
charset
is the canonical name of a character set.
codecname
is the name of a Python codec, as appropriate for the second argument to the
unicode()
built-in, or to the
encode()
method of a Unicode string.