email.charset
: Representing character sets
¶
源代码： Lib/email/charset.py
This module is part of the legacy (
Compat32
) email API. In the new API only the aliases table is used.
The remaining text in this section is the original documentation of the module.
This module provides a class
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
package.
Import this class from the
email.charset
模块。
email.charset.
Charset
(
input_charset=DEFAULT_CHARSET
)
¶
Map character sets to their email properties.
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
character set.
Charset
instances have the following data attributes:
input_charset
¶
The initial character set specified. Common aliases are converted to their
official
email names (e.g.
latin_1
is converted to
iso-8859-1
). Defaults to 7-bit
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
instances also have the following methods:
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.
Returns the string
quoted-printable
if
body_encoding
is
QP
, returns the string
base64
if
body_encoding
is
BASE64
, and returns the string
7bit
否则。
get_output_charset
(
)
¶
Return the output character set.
This is the
output_charset
attribute if that is not
None
, otherwise it is
input_charset
.
header_encode
(
string
)
¶
Header-encode the string string .
The type of encoding (base64 or quoted-printable) will be based on the header_encoding 属性。
header_encode_lines
(
string
,
maxlengths
)
¶
Header-encode a string by converting it first to bytes.
This is similar to
header_encode()
except that the string is fit into maximum line lengths as given by the argument
maxlengths
, which must be an iterator: each element returned from this iterator will provide the next maximum line length.
body_encode
(
string
)
¶
Body-encode the string string .
The type of encoding (base64 or quoted-printable) will be based on the body_encoding 属性。
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__()
is an alias for
__str__()
.
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=None
,
body_enc=None
,
output_charset=None
)
¶
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
.