增量编码和解码
¶
The
IncrementalEncoder
and
IncrementalDecoder
classes provide the basic interface for incremental encoding and decoding. Encoding/decoding the input isn’t done with one call to the stateless encoder/decoder function, but with multiple calls to the
encode()
/
decode()
method of the incremental encoder/decoder. The incremental encoder/decoder keeps track of the encoding/decoding process during method calls.
The joined output of calls to the
encode()
/
decode()
method is the same as if all the single inputs were joined into one, and this input was encoded/decoded with the stateless encoder/decoder.
IncrementalEncoder 对象
¶
The
IncrementalEncoder
class is used for encoding an input in multiple steps. It defines the following methods which every incremental encoder must define in order to be compatible with the Python codec registry.
-
class
codecs.
IncrementalEncoder
(
errors
=
'strict'
)
¶
-
构造函数为
IncrementalEncoder
实例。
All incremental encoders must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The
IncrementalEncoder
may implement different error handling schemes by providing the
errors
keyword argument. See
错误处理程序
了解可能值。
The
errors
argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the
IncrementalEncoder
对象。
-
encode
(
object
,
final
=
False
)
¶
-
编码
object
(taking the current state of the encoder into account) and returns the resulting encoded object. If this is the last call to
encode()
final
must be true (the default is false).
-
reset
(
)
¶
-
Reset the encoder to the initial state. The output is discarded: call
.encode(object, final=True)
, passing an empty byte or text string if necessary, to reset the encoder and to get the output.
-
getstate
(
)
¶
-
Return the current state of the encoder which must be an integer. The implementation should make sure that
0
is the most common state. (States that are more complicated than integers can be converted into an integer by marshaling/pickling the state and encoding the bytes of the resulting string into an integer.)
-
setstate
(
state
)
¶
-
Set the state of the encoder to
state
.
state
must be an encoder state returned by
getstate()
.
IncrementalDecoder 对象
¶
The
IncrementalDecoder
class is used for decoding an input in multiple steps. It defines the following methods which every incremental decoder must define in order to be compatible with the Python codec registry.
-
class
codecs.
IncrementalDecoder
(
errors
=
'strict'
)
¶
-
构造函数为
IncrementalDecoder
实例。
All incremental decoders must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The
IncrementalDecoder
may implement different error handling schemes by providing the
errors
keyword argument. See
错误处理程序
了解可能值。
The
errors
argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the
IncrementalDecoder
对象。
-
decode
(
object
,
final
=
False
)
¶
-
解码
object
(taking the current state of the decoder into account) and returns the resulting decoded object. If this is the last call to
decode()
final
must be true (the default is false). If
final
is true the decoder must decode the input completely and must flush all buffers. If this isn’t possible (e.g. because of incomplete byte sequences at the end of the input) it must initiate error handling just like in the stateless case (which might raise an exception).
-
reset
(
)
¶
-
将解码器重置到初始状态。
-
getstate
(
)
¶
-
Return the current state of the decoder. This must be a tuple with two items, the first must be the buffer containing the still undecoded input. The second must be an integer and can be additional state info. (The implementation should make sure that
0
is the most common additional state info.) If this additional state info is
0
it must be possible to set the decoder to the state which has no input buffered and
0
as the additional state info, so that feeding the previously buffered input to the decoder returns it to the previous state without producing any output. (Additional state info that is more complicated than integers can be converted into an integer by marshaling/pickling the info and encoding the bytes of the resulting string into an integer.)
-
setstate
(
state
)
¶
-
Set the state of the decoder to
state
.
state
must be a decoder state returned by
getstate()
.
流编码和解码
¶
The
StreamWriter
and
StreamReader
classes provide generic working interfaces which can be used to implement new encoding submodules very easily. See
encodings.utf_8
for an example of how this is done.
StreamWriter 对象
¶
The
StreamWriter
类是子类化的
Codec
and defines the following methods which every stream writer must define in order to be compatible with the Python codec registry.
-
class
codecs.
StreamWriter
(
stream
,
errors
=
'strict'
)
¶
-
构造函数为
StreamWriter
实例。
All stream writers must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The
stream
argument must be a file-like object open for writing text or binary data, as appropriate for the specific codec.
The
StreamWriter
may implement different error handling schemes by providing the
errors
keyword argument. See
错误处理程序
for the standard error handlers the underlying stream codec may support.
The
errors
argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the
StreamWriter
对象。
-
write
(
object
)
¶
-
Writes the object’s contents encoded to the stream.
-
writelines
(
list
)
¶
-
Writes the concatenated iterable of strings to the stream (possibly by reusing the
write()
method). Infinite or very large iterables are not supported. The standard bytes-to-bytes codecs do not support this method.
-
reset
(
)
¶
-
Resets the codec buffers used for keeping internal state.
Calling this method should ensure that the data on the output is put into a clean state that allows appending of new fresh data without having to rescan the whole stream to recover state.
In addition to the above methods, the
StreamWriter
must also inherit all other methods and attributes from the underlying stream.
StreamReader 对象
¶
The
StreamReader
类是子类化的
Codec
and defines the following methods which every stream reader must define in order to be compatible with the Python codec registry.
-
class
codecs.
StreamReader
(
stream
,
errors
=
'strict'
)
¶
-
构造函数为
StreamReader
实例。
All stream readers must provide this constructor interface. They are free to add additional keyword arguments, but only the ones defined here are used by the Python codec registry.
The
stream
argument must be a file-like object open for reading text or binary data, as appropriate for the specific codec.
The
StreamReader
may implement different error handling schemes by providing the
errors
keyword argument. See
错误处理程序
for the standard error handlers the underlying stream codec may support.
The
errors
argument will be assigned to an attribute of the same name. Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the
StreamReader
对象。
The set of allowed values for the
errors
argument can be extended with
register_error()
.
-
read
(
size
=
-1
,
chars
=
-1
,
firstline
=
False
)
¶
-
Decodes data from the stream and returns the resulting object.
The
chars
argument indicates the number of decoded code points or bytes to return. The
read()
method will never return more data than requested, but it might return less, if there is not enough available.
The
size
argument indicates the approximate maximum number of encoded bytes or code points to read for decoding. The decoder can modify this setting as appropriate. The default value -1 indicates to read and decode as much as possible. This parameter is intended to prevent having to decode huge files in one step.
The
firstline
flag indicates that it would be sufficient to only return the first line, if there are decoding errors on later lines.
The method should use a greedy read strategy meaning that it should read as much data as is allowed within the definition of the encoding and the given size, e.g. if optional encoding endings or state markers are available on the stream, these should be read too.
-
readline
(
size
=
None
,
keepends
=
True
)
¶
-
Read one line from the input stream and return the decoded data.
size
, if given, is passed as size argument to the stream’s
read()
方法。
若
keepends
is false line-endings will be stripped from the lines returned.
-
readlines
(
sizehint
=
None
,
keepends
=
True
)
¶
-
Read all lines available on the input stream and return them as a list of lines.
Line-endings are implemented using the codec’s
decode()
method and are included in the list entries if
keepends
为 True。
sizehint
, if given, is passed as the
size
argument to the stream’s
read()
方法。
-
reset
(
)
¶
-
Resets the codec buffers used for keeping internal state.
Note that no stream repositioning should take place. This method is primarily intended to be able to recover from decoding errors.
In addition to the above methods, the
StreamReader
must also inherit all other methods and attributes from the underlying stream.
StreamReaderWriter 对象
¶
The
StreamReaderWriter
is a convenience class that allows wrapping streams which work in both read and write modes.
The design is such that one can use the factory functions returned by the
lookup()
function to construct the instance.
-
class
codecs.
StreamReaderWriter
(
stream
,
Reader
,
Writer
,
errors
=
'strict'
)
¶
-
创建
StreamReaderWriter
实例。
stream
must be a file-like object.
Reader
and
Writer
must be factory functions or classes providing the
StreamReader
and
StreamWriter
interface resp. Error handling is done in the same way as defined for the stream readers and writers.
StreamReaderWriter
instances define the combined interfaces of
StreamReader
and
StreamWriter
classes. They inherit all other methods and attributes from the underlying stream.
StreamWriter 对象
¶
The
StreamRecoder
translates data from one encoding to another, which is sometimes useful when dealing with different encoding environments.
The design is such that one can use the factory functions returned by the
lookup()
function to construct the instance.
-
class
codecs.
StreamRecoder
(
stream
,
encode
,
decode
,
Reader
,
Writer
,
errors
=
'strict'
)
¶
-
创建
StreamRecoder
instance which implements a two-way conversion:
encode
and
decode
work on the frontend — the data visible to code calling
read()
and
write()
，而
Reader
and
Writer
work on the backend — the data in
stream
.
You can use these objects to do transparent transcodings, e.g., from Latin-1 to UTF-8 and back.
The
stream
自变量必须是像文件对象。
The
encode
and
decode
arguments must adhere to the
Codec
接口。
Reader
and
Writer
must be factory functions or classes providing objects of the
StreamReader
and
StreamWriter
interface respectively.
Error handling is done in the same way as defined for the stream readers and writers.
StreamRecoder
instances define the combined interfaces of
StreamReader
and
StreamWriter
classes. They inherit all other methods and attributes from the underlying stream.
编码和 Unicode
¶
Strings are stored internally as sequences of code points in range
U+0000
–
U+10FFFF
。(见
PEP 393
for more details about the implementation.) Once a string object is used outside of CPU and memory, endianness and how these arrays are stored as bytes become an issue. As with other codecs, serialising a string into a sequence of bytes is known as
encoding
, and recreating the string from the sequence of bytes is known as
decoding
. There are a variety of different text serialisation codecs, which are collectivity referred to as
文本编码
.
The simplest text encoding (called
'latin-1'
or
'iso-8859-1'
) maps the code points 0–255 to the bytes
0x0
–
0xff
, which means that a string object that contains code points above
U+00FF
can’t be encoded with this codec. Doing so will raise a
UnicodeEncodeError
that looks like the following (although the details of the error message may differ):
UnicodeEncodeError: 'latin-1' codec can't encode character '\u1234' in
position 3: ordinal not in range(256)
.
There’s another group of encodings (the so called charmap encodings) that choose a different subset of all Unicode code points and how these code points are mapped to the bytes
0x0
–
0xff
. To see how this is done simply open e.g.
encodings/cp1252.py
(which is an encoding that is used primarily on Windows). There’s a string constant with 256 characters that shows you which character is mapped to which byte value.
All of these encodings can only encode 256 of the 1114112 code points defined in Unicode. A simple and straightforward way that can store each Unicode code point, is to store each code point as four consecutive bytes. There are two possibilities: store the bytes in big endian or in little endian order. These two encodings are called
UTF-32-BE
and
UTF-32-LE
respectively. Their disadvantage is that if e.g. you use
UTF-32-BE
on a little endian machine you will always have to swap bytes on encoding and decoding.
UTF-32
avoids this problem: bytes will always be in natural endianness. When these bytes are read by a CPU with a different endianness, then bytes have to be swapped though. To be able to detect the endianness of a
UTF-16
or
UTF-32
byte sequence, there’s the so called BOM (“Byte Order Mark”). This is the Unicode character
U+FEFF
. This character can be prepended to every
UTF-16
or
UTF-32
byte sequence. The byte swapped version of this character (
0xFFFE
) is an illegal character that may not appear in a Unicode text. So when the first character in a
UTF-16
or
UTF-32
byte sequence appears to be a
U+FFFE
the bytes have to be swapped on decoding. Unfortunately the character
U+FEFF
had a second purpose as a
ZERO WIDTH NO-BREAK SPACE
: a character that has no width and doesn’t allow a word to be split. It can e.g. be used to give hints to a ligature algorithm. With Unicode 4.0 using
U+FEFF
作为
ZERO WIDTH NO-BREAK SPACE
has been deprecated (with
U+2060
(
WORD JOINER
) assuming this role). Nevertheless Unicode software still must be able to handle
U+FEFF
in both roles: as a BOM it’s a device to determine the storage layout of the encoded bytes, and vanishes once the byte sequence has been decoded into a string; as a
ZERO WIDTH
NO-BREAK SPACE
it’s a normal character that will be decoded like any other.
There’s another encoding that is able to encode the full range of Unicode characters: UTF-8. UTF-8 is an 8-bit encoding, which means there are no issues with byte order in UTF-8. Each byte in a UTF-8 byte sequence consists of two parts: marker bits (the most significant bits) and payload bits. The marker bits are a sequence of zero to four
1
bits followed by a
0
bit. Unicode characters are encoded like this (with x being payload bits, which when concatenated give the Unicode character):
|
范围
|
编码
|
|
U-00000000
…
U-0000007F
|
0xxxxxxx
|
|
U-00000080
…
U-000007FF
|
110xxxxx 10xxxxxx
|
|
U-00000800
…
U-0000FFFF
|
1110xxxx 10xxxxxx 10xxxxxx
|
|
U-00010000
…
U-0010FFFF
|
11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
|
The least significant bit of the Unicode character is the rightmost x bit.
As UTF-8 is an 8-bit encoding no BOM is required and any
U+FEFF
character in the decoded string (even if it’s the first character) is treated as a
ZERO
WIDTH NO-BREAK SPACE
.
Without external information it’s impossible to reliably determine which encoding was used for encoding a string. Each charmap encoding can decode any random byte sequence. However that’s not possible with UTF-8, as UTF-8 byte sequences have a structure that doesn’t allow arbitrary byte sequences. To increase the reliability with which a UTF-8 encoding can be detected, Microsoft invented a variant of UTF-8 (that Python calls
"utf-8-sig"
) for its Notepad program: Before any of the Unicode characters is written to the file, a UTF-8 encoded BOM (which looks like this as a byte sequence:
0xef
,
0xbb
,
0xbf
) is written. As it’s rather improbable that any charmap encoded file starts with these byte values (which would e.g. map to
LATIN SMALL LETTER I WITH DIAERESIS
RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
INVERTED QUESTION MARK
in iso-8859-1), this increases the probability that a
utf-8-sig
encoding can be correctly guessed from the byte sequence. So here the BOM is not used to be able to determine the byte order used for generating the byte sequence, but as a signature that helps in guessing the encoding. On encoding the utf-8-sig codec will write
0xef
,
0xbb
,
0xbf
as the first three bytes to the file. On decoding
utf-8-sig
will skip those three bytes if they appear as the first three bytes in the file. In UTF-8, the use of the BOM is discouraged and should generally be avoided.
标准编码
¶
Python comes with a number of codecs built-in, either implemented as C functions or with dictionaries as mapping tables. The following table lists the codecs by name, together with a few common aliases, and the languages for which the encoding is likely used. Neither the list of aliases nor the list of languages is meant to be exhaustive. Notice that spelling alternatives that only differ in case or use a hyphen instead of an underscore are also valid aliases; therefore, e.g.
'utf-8'
is a valid alias for the
'utf_8'
编解码器。
CPython 实现细节：
Some common encodings can bypass the codecs lookup machinery to improve performance. These optimization opportunities are only recognized by CPython for a limited set of (case insensitive) aliases: utf-8, utf8, latin-1, latin1, iso-8859-1, iso8859-1, mbcs (Windows only), ascii, us-ascii, utf-16, utf16, utf-32, utf32, and the same using underscores instead of dashes. Using alternative aliases for these encodings may result in slower execution.
3.6 版改变：
Optimization opportunity recognized for us-ascii.
Many of the character sets support the same languages. They vary in individual characters (e.g. whether the EURO SIGN is supported or not), and in the assignment of characters to code positions. For the European languages in particular, the following variants typically exist:
|
编解码器
|
别名
|
语言
|
|
ascii
|
646, us-ascii
|
English
|
|
big5
|
big5-tw, csbig5
|
繁体中文
|
|
big5hkscs
|
big5-hkscs, hkscs
|
繁体中文
|
|
cp037
|
IBM037, IBM039
|
English
|
|
cp273
|
273, IBM273, csIBM273
|
德语
Added in version 3.4.
|
|
cp424
|
EBCDIC-CP-HE, IBM424
|
希伯来语
|
|
cp437
|
437, IBM437
|
English
|
|
cp500
|
EBCDIC-CP-BE, EBCDIC-CP-CH, IBM500
|
西欧
|
|
cp720
|
|
阿拉伯语
|
|
cp737
|
|
希腊语
|
|
cp775
|
IBM775
|
波罗的语
|
|
cp850
|
850, IBM850
|
西欧
|
|
cp852
|
852, IBM852
|
中东欧
|
|
cp855
|
855, IBM855
|
Bulgarian, Byelorussian, Macedonian, Russian, Serbian
|
|
cp856
|
|
希伯来语
|
|
cp857
|
857, IBM857
|
土耳其语
|
|
cp858
|
858, IBM858
|
西欧
|
|
cp860
|
860, IBM860
|
葡萄牙语
|
|
cp861
|
861, CP-IS, IBM861
|
冰岛语
|
|
cp862
|
862, IBM862
|
希伯来语
|
|
cp863
|
863, IBM863
|
加拿大
|
|
cp864
|
IBM864
|
阿拉伯语
|
|
cp865
|
865, IBM865
|
Danish, Norwegian
|
|
cp866
|
866, IBM866
|
俄语
|
|
cp869
|
869, CP-GR, IBM869
|
希腊语
|
|
cp874
|
|
泰语
|
|
cp875
|
|
希腊语
|
|
cp932
|
932, ms932, mskanji, ms-kanji, windows-31j
|
日语
|
|
cp949
|
949, ms949, uhc
|
韩语
|
|
cp950
|
950, ms950
|
繁体中文
|
|
cp1006
|
|
乌尔都语
|
|
cp1026
|
ibm1026
|
土耳其语
|
|
cp1125
|
1125, ibm1125, cp866u, ruscii
|
乌克兰语
Added in version 3.4.
|
|
cp1140
|
ibm1140
|
西欧
|
|
cp1250
|
windows-1250
|
中东欧
|
|
cp1251
|
windows-1251
|
Bulgarian, Byelorussian, Macedonian, Russian, Serbian
|
|
cp1252
|
windows-1252
|
西欧
|
|
cp1253
|
windows-1253
|
希腊语
|
|
cp1254
|
windows-1254
|
土耳其语
|
|
cp1255
|
windows-1255
|
希伯来语
|
|
cp1256
|
windows-1256
|
阿拉伯语
|
|
cp1257
|
windows-1257
|
波罗的语
|
|
cp1258
|
windows-1258
|
越南语
|
|
euc_jp
|
eucjp, ujis, u-jis
|
日语
|
|
euc_jis_2004
|
jisx0213, eucjis2004
|
日语
|
|
euc_jisx0213
|
eucjisx0213
|
日语
|
|
euc_kr
|
euckr, korean, ksc5601, ks_c-5601, ks_c-5601-1987, ksx1001, ks_x-1001
|
韩语
|
|
gb2312
|
chinese, csiso58gb231280, euc-cn, euccn, eucgb2312-cn, gb2312-1980, gb2312-80, iso-ir-58
|
简体中文
|
|
gbk
|
936, cp936, ms936
|
Unified Chinese
|
|
gb18030
|
gb18030-2000
|
Unified Chinese
|
|
hz
|
hzgb, hz-gb, hz-gb-2312
|
简体中文
|
|
iso2022_jp
|
csiso2022jp, iso2022jp, iso-2022-jp
|
日语
|
|
iso2022_jp_1
|
iso2022jp-1, iso-2022-jp-1
|
日语
|
|
iso2022_jp_2
|
iso2022jp-2, iso-2022-jp-2
|
Japanese, Korean, Simplified Chinese, Western Europe, Greek
|
|
iso2022_jp_2004
|
iso2022jp-2004, iso-2022-jp-2004
|
日语
|
|
iso2022_jp_3
|
iso2022jp-3, iso-2022-jp-3
|
日语
|
|
iso2022_jp_ext
|
iso2022jp-ext, iso-2022-jp-ext
|
日语
|
|
iso2022_kr
|
csiso2022kr, iso2022kr, iso-2022-kr
|
韩语
|
|
latin_1
|
iso-8859-1, iso8859-1, 8859, cp819, latin, latin1, L1
|
西欧
|
|
iso8859_2
|
iso-8859-2, latin2, L2
|
中东欧
|
|
iso8859_3
|
iso-8859-3, latin3, L3
|
Esperanto, Maltese
|
|
iso8859_4
|
iso-8859-4, latin4, L4
|
波罗的语
|
|
iso8859_5
|
iso-8859-5, cyrillic
|
Bulgarian, Byelorussian, Macedonian, Russian, Serbian
|
|
iso8859_6
|
iso-8859-6, arabic
|
阿拉伯语
|
|
iso8859_7
|
iso-8859-7, greek, greek8
|
希腊语
|
|
iso8859_8
|
iso-8859-8, hebrew
|
希伯来语
|
|
iso8859_9
|
iso-8859-9, latin5, L5
|
土耳其语
|
|
iso8859_10
|
iso-8859-10, latin6, L6
|
Nordic languages
|
|
iso8859_11
|
iso-8859-11, thai
|
泰语
|
|
iso8859_13
|
iso-8859-13, latin7, L7
|
波罗的语
|
|
iso8859_14
|
iso-8859-14, latin8, L8
|
Celtic languages
|
|
iso8859_15
|
iso-8859-15, latin9, L9
|
西欧
|
|
iso8859_16
|
iso-8859-16, latin10, L10
|
东南欧
|
|
johab
|
cp1361, ms1361
|
韩语
|
|
koi8_r
|
|
俄语
|
|
koi8_t
|
|
Tajik
Added in version 3.5.
|
|
koi8_u
|
|
乌克兰语
|
|
kz1048
|
kz_1048, strk1048_2002, rk1048
|
Kazakh
Added in version 3.5.
|
|
mac_cyrillic
|
maccyrillic
|
Bulgarian, Byelorussian, Macedonian, Russian, Serbian
|
|
mac_greek
|
macgreek
|
希腊语
|
|
mac_iceland
|
maciceland
|
冰岛语
|
|
mac_latin2
|
maclatin2, maccentraleurope, mac_centeuro
|
中东欧
|
|
mac_roman
|
macroman, macintosh
|
西欧
|
|
mac_turkish
|
macturkish
|
土耳其语
|
|
ptcp154
|
csptcp154, pt154, cp154, cyrillic-asian
|
Kazakh
|
|
shift_jis
|
csshiftjis, shiftjis, sjis, s_jis
|
日语
|
|
shift_jis_2004
|
shiftjis2004, sjis_2004, sjis2004
|
日语
|
|
shift_jisx0213
|
shiftjisx0213, sjisx0213, s_jisx0213
|
日语
|
|
utf_32
|
U32, utf32
|
所有语言
|
|
utf_32_be
|
UTF-32BE
|
所有语言
|
|
utf_32_le
|
UTF-32LE
|
所有语言
|
|
utf_16
|
U16, utf16
|
所有语言
|
|
utf_16_be
|
UTF-16BE
|
所有语言
|
|
utf_16_le
|
UTF-16LE
|
所有语言
|
|
utf_7
|
U7, unicode-1-1-utf-7
|
所有语言
|
|
utf_8
|
U8, UTF, utf8, cp65001
|
所有语言
|
|
utf_8_sig
|
|
所有语言
|
3.4 版改变：
The utf-16* and utf-32* encoders no longer allow surrogate code points (
U+D800
–
U+DFFF
) to be encoded. The utf-32* decoders no longer decode byte sequences that correspond to surrogate code points.
3.8 版改变：
cp65001
现在是别名化的
utf_8
.
Python 特定编码
¶
A number of predefined codecs are specific to Python, so their codec names have no meaning outside Python. These are listed in the tables below based on the expected input and output types (note that while text encodings are the most common use case for codecs, the underlying codec infrastructure supports arbitrary data transforms rather than just text encodings). For asymmetric codecs, the stated meaning describes the encoding direction.
文本编码
¶
以下编解码器提供
str
to
bytes
编码和
像字节对象
to
str
解码，类似 Unicode 文本编码。
|
编解码器
|
别名
|
含义
|
|
idna
|
|
实现
RFC 3490
，另请参阅
encodings.idna
. Only
errors='strict'
is supported.
|
|
mbcs
|
ansi, dbcs
|
Windows only: Encode the operand according to the ANSI codepage (CP_ACP).
|
|
oem
|
|
Windows only: Encode the operand according to the OEM codepage (CP_OEMCP).
Added in version 3.6.
|
|
palmos
|
|
Encoding of PalmOS 3.5.
|
|
punycode
|
|
实现
RFC 3492
. Stateful codecs are not supported.
|
|
raw_unicode_escape
|
|
Latin-1 encoding with
\uXXXX
and
\UXXXXXXXX
for other code points. Existing backslashes are not escaped in any way. It is used in the Python pickle protocol.
|
|
undefined
|
|
Raise an exception for all conversions, even empty strings. The error handler is ignored.
|
|
unicode_escape
|
|
Encoding suitable as the contents of a Unicode literal in ASCII-encoded Python source code, except that quotes are not escaped. Decode from Latin-1 source code. Beware that Python source code actually uses UTF-8 by default.
|
3.8 版改变：
移除 unicode_internal 编解码器。
文本变换
¶
以下编解码器提供文本变换：
str
to
str
mapping. It is not supported by
str.encode()
(which only produces
bytes
输出)。
|
编解码器
|
别名
|
含义
|
|
rot_13
|
rot13
|
Return the Caesar-cypher encryption of the operand.
|
Added in version 3.2:
Restoration of the
rot_13
文本变换。
3.4 版改变：
Restoration of the
rot13
别名。
本模块实现
RFC 3490
(Internationalized Domain Names in Applications) and
RFC 3492
(Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)). It builds upon the
punycode
编码和
stringprep
.
If you need the IDNA 2008 standard from
RFC 5891
and
RFC 5895
, use the third-party
idna
模块。
These RFCs together define a protocol to support non-ASCII characters in domain names. A domain name containing non-ASCII characters (such as
www.Alliancefrançaise.nu
) is converted into an ASCII-compatible encoding (ACE, such as
www.xn--alliancefranaise-npb.nu
). The ACE form of the domain name is then used in all places where arbitrary characters are not allowed by the protocol, such as DNS queries, HTTP
fields, and so on. This conversion is carried out in the application; if possible invisible to the user: The application should transparently convert Unicode domain labels to IDNA on the wire, and convert back ACE labels to Unicode before presenting them to the user.
Python supports this conversion in several ways: the
idna
codec performs conversion between Unicode and ACE, separating an input string into labels based on the separator characters defined in
section 3.1 of RFC 3490
and converting each label to ACE as required, and conversely separating an input byte string into labels based on the
.
separator and converting any ACE labels found into unicode. Furthermore, the
socket
module transparently converts Unicode host names to ACE, so that applications need not be concerned about converting host names themselves when they pass them to the socket module. On top of that, modules that have host names as function parameters, such as
http.client
and
ftplib
, accept Unicode host names (
http.client
then also transparently sends an IDNA hostname in the
field if it sends that field at all).
When receiving host names from the wire (such as in reverse name lookup), no automatic conversion to Unicode is performed: applications wishing to present such host names to the user should decode them to Unicode.
模块
encodings.idna
also implements the nameprep procedure, which performs certain normalizations on host names, to achieve case-insensitivity of international domain names, and to unify similar characters. The nameprep functions can be used directly if desired.
-
encodings.idna.
nameprep
(
label
)
¶
-
Return the nameprepped version of
label
. The implementation currently assumes query strings, so
AllowUnassigned
为 True。
-
encodings.idna.
ToASCII
(
label
)
¶
-
Convert a label to ASCII, as specified in
RFC 3490
.
UseSTD3ASCIIRules
is assumed to be false.
-
encodings.idna.
ToUnicode
(
label
)
¶
-
Convert a label to Unicode, as specified in
RFC 3490
.
This module implements the ANSI codepage (CP_ACP).
可用性
：Windows。
3.2 版改变：
在 3.2 之前，
errors
自变量被忽略；
'replace'
始终用于编码，和
'ignore'
以解码。
3.3 版改变：
支持任何错误处理程序。
This module implements a variant of the UTF-8 codec. On encoding, a UTF-8 encoded BOM will be prepended to the UTF-8 encoded bytes. For the stateful encoder this is only done once (on the first write to the byte stream). On decoding, an optional UTF-8 encoded BOM at the start of the data will be skipped.
