7.8. `codecs` — 编解码器注册和基类 ¶

This module defines base classes for standard Python codecs (encoders and decoders) and provides access to the internal Python codec registry which manages the codec and error handling lookup process.

It defines the following functions:

codecs. encode ( obj [ , encoding [ , errors ] ] ) ¶

codecs. decode ( obj [ , encoding [ , errors ] ] ) ¶

codecs. register ( search_function ) ¶

codecs. lookup ( encoding ) ¶

To simplify access to the various codecs, the module provides these additional functions which use lookup() for the codec lookup:

codecs. getencoder ( encoding ) ¶

codecs. getdecoder ( encoding ) ¶

codecs. getincrementalencoder ( encoding ) ¶

codecs. getincrementaldecoder ( encoding ) ¶

codecs. getreader ( encoding ) ¶

codecs. getwriter ( encoding ) ¶

codecs. register_error ( 名称 , error_handler ) ¶

codecs. lookup_error ( 名称 ) ¶

codecs. strict_errors ( exception ) ¶

codecs. replace_errors ( exception ) ¶

codecs. ignore_errors ( exception ) ¶

codecs. xmlcharrefreplace_errors ( exception ) ¶

codecs. backslashreplace_errors ( exception ) ¶

To simplify working with encoded files or stream, the module also defines these utility functions:

codecs. open ( filename , mode [ , encoding [ , errors [ , buffering ] ] ] ) ¶

codecs. EncodedFile ( file , input [ , output [ , errors ] ] ) ¶

codecs. iterencode ( iterable , encoding [ , errors ] ) ¶

codecs. iterdecode ( iterable , encoding [ , errors ] ) ¶

The module also provides the following constants which are useful for reading and writing to platform dependent files:

codecs. BOM ¶
codecs. BOM_BE ¶
codecs. BOM_LE ¶
codecs. BOM_UTF8 ¶
codecs. BOM_UTF16 ¶
codecs. BOM_UTF16_BE ¶
codecs. BOM_UTF16_LE ¶
codecs. BOM_UTF32 ¶
codecs. BOM_UTF32_BE ¶
codecs. BOM_UTF32_LE ¶

7.8.1. 编解码器基类 ¶

The codecs module defines a set of base classes which define the interface and can also be used to easily write your own codecs for use in Python.

Each codec has to define four interfaces to make it usable as codec in Python: stateless encoder, stateless decoder, stream reader and stream writer. The stream reader and writers typically reuse the stateless encoder/decoder to implement the file protocols.

The Codec class defines the interface for stateless encoders/decoders.

To simplify and standardize error handling, the encode() and decode() methods may implement different error handling schemes by providing the errors string argument. The following string values are defined and implemented by all standard Python codecs:

值	含义
`'strict'`	引发 `UnicodeError` (or a subclass); this is the default.
`'ignore'`	Ignore the character and continue with the next.
`'replace'`	Replace with a suitable replacement character; Python will use the official U+FFFD REPLACEMENT CHARACTER for the built-in Unicode codecs on decoding and ‘?’ on encoding.
`'xmlcharrefreplace'`	Replace with the appropriate XML character reference (only for encoding).
`'backslashreplace'`	Replace with backslashed escape sequences (only for encoding).

The set of allowed values can be extended via register_error() .

7.8.1.1. Codec Objects ¶

The Codec class defines these methods which also define the function interfaces of the stateless encoder and decoder:

Codec. encode ( input [ , errors ] ) ¶

Codec. decode ( input [ , errors ] ) ¶

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.

7.8.1.2. IncrementalEncoder 对象 ¶

2.5 版新增。

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 ] ) ¶

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. These parameters are predefined:

'strict' 引发 ValueError (or a subclass); this is the default.
'ignore' Ignore the character and continue with the next.
'replace' Replace with a suitable replacement character
'xmlcharrefreplace' Replace with the appropriate XML character reference
'backslashreplace' Replace with backslashed escape sequences.

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。

The set of allowed values for the errors argument can be extended with register_error() .

encode ( 对象 [ , final ] ) ¶

reset ( ) ¶: Reset the encoder to the initial state.

7.8.1.3. 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 ] ) ¶

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. These parameters are predefined:

'strict' 引发 ValueError (or a subclass); this is the default.
'ignore' Ignore the character and continue with the next.
'replace' Replace with a suitable replacement character.

The set of allowed values for the errors argument can be extended with register_error() .

decode ( 对象 [ , final ] ) ¶

reset ( ) ¶: 将解码器重置到初始状态。

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.

7.8.1.4. 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 ] ) ¶

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.

stream must be a file-like object open for writing binary data.

The StreamWriter may implement different error handling schemes by providing the errors keyword argument. These parameters are predefined:

'strict' 引发 ValueError (or a subclass); this is the default.
'ignore' Ignore the character and continue with the next.
'replace' Replace with a suitable replacement character
'xmlcharrefreplace' Replace with the appropriate XML character reference
'backslashreplace' Replace with backslashed escape sequences.

The set of allowed values for the errors argument can be extended with register_error() .

write ( 对象 ) ¶: Writes the object’s contents encoded to the stream.

writelines ( list ) ¶: Writes the concatenated list of strings to the stream (possibly by reusing the write() 方法)。

reset ( ) ¶

Flushes and resets the codec buffers used for keeping 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.

7.8.1.5. 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 ] ) ¶

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.

stream must be a file-like object open for reading (binary) data.

The StreamReader may implement different error handling schemes by providing the errors keyword argument. These parameters are defined:

'strict' 引发 ValueError (or a subclass); this is the default.
'ignore' Ignore the character and continue with the next.
'replace' Replace with a suitable replacement character.

The set of allowed values for the errors argument can be extended with register_error() .

read ( [ size [ , chars [ , firstline ] ] ] ) ¶

Decodes data from the stream and returns the resulting object.

chars indicates the number of characters to read from the stream. read() will never return more than chars characters, but it might return less, if there are not enough characters available.

size indicates the approximate maximum number of bytes to read from the stream for decoding purposes. The decoder can modify this setting as appropriate. The default value -1 indicates to read and decode as much as possible. size is intended to prevent having to decode huge files in one step.

firstline 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.

2.4 版改变： chars argument added.

Changed in version 2.4.2: firstline argument added.

readline ( [ size [ , keepends ] ] ) ¶

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.

2.4 版改变： keepends argument added.

readlines ( [ sizehint [ , keepends ] ] ) ¶

Read all lines available on the input stream and return them as a list of lines.

Line-endings are implemented using the codec’s decoder 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 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.

The next two base classes are included for convenience. They are not needed by the codec registry, but may provide useful in practice.

7.8.1.6. StreamReaderWriter 对象 ¶

The StreamReaderWriter 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 ) ¶: 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.

7.8.1.7. StreamWriter 对象 ¶

The StreamRecoder provide a frontend - backend view of encoding data 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 ) ¶

创建 StreamRecoder instance which implements a two-way conversion: encode and decode work on the frontend (the input to read() and output of write() ) while Reader and Writer work on the backend (reading and writing to the stream).

You can use these objects to do transparent direct recodings from e.g. Latin-1 to UTF-8 and back.

stream must be a file-like object.

encode , decode must adhere to the Codec 接口。 Reader , Writer must be factory functions or classes providing objects of the StreamReader and StreamWriter interface respectively.

encode and decode are needed for the frontend translation, Reader and Writer for the backend translation. The intermediate format used is determined by the two sets of codecs, e.g. the Unicode codecs will use Unicode as the intermediate encoding.

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.

7.8.2. 编码和 Unicode ¶

Unicode strings are stored internally as sequences of code points (to be precise as Py_UNICODE arrays). Depending on the way Python is compiled (either via --enable-unicode=ucs2 or --enable-unicode=ucs4 , with the former being the default) Py_UNICODE is either a 16-bit or 32-bit data type. Once a Unicode object is used outside of CPU and memory, CPU endianness and how these arrays are stored as bytes become an issue. Transforming a unicode object into a sequence of bytes is called encoding and recreating the unicode object from the sequence of bytes is known as decoding. There are many different methods for how this transformation can be done (these methods are also called encodings). The simplest method is to map the code points 0–255 to the bytes 0x0 – 0xff . This means that a unicode object that contains code points above U+00FF can’t be encoded with this method (which is called 'latin-1' or 'iso-8859-1' ). unicode.encode() 将引发 UnicodeEncodeError that looks like this: UnicodeEncodeError: 'latin-1' codec can't encode character u'\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 an 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 Unicode 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 encoding 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 Unicode 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 Unicode 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 2.5 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.

7.8.3. 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。

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:

ISO 8859 代码集
a Microsoft Windows code page, which is typically derived from an 8859 codeset, but replaces control characters with additional graphic characters
IBM EBCDIC 代码页
IBM PC 代码页，兼容 ASCII

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
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	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
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	West Europe
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_u		乌克兰语
mac_cyrillic	maccyrillic	Bulgarian, Byelorussian, Macedonian, Russian, Serbian
mac_greek	macgreek	希腊语
mac_iceland	maciceland	冰岛语
mac_latin2	maclatin2, maccentraleurope	中东欧
mac_roman	macroman	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	all languages (BMP only)
utf_16_le	UTF-16LE	all languages (BMP only)
utf_7	U7, unicode-1-1-utf-7	所有语言
utf_8	U8, UTF, utf8	所有语言
utf_8_sig		所有语言

7.8.4. 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 purpose describes the encoding direction.

The following codecs provide unicode-to-str encoding 1 and str-to-unicode decoding 2 , similar to the Unicode text encodings.

编解码器	别名	目的
idna		实现 RFC 3490 ，另请参阅 `encodings.idna`
mbcs	dbcs	Windows only: Encode operand according to the ANSI codepage (CP_ACP)
palmos		Encoding of PalmOS 3.5
punycode		实现 RFC 3492
raw_unicode_escape		Produce a string that is suitable as raw Unicode literal in Python source code
rot_13	rot13	Returns the Caesar-cypher encryption of the operand
undefined		Raise an exception for all conversions. Can be used as the system encoding if no automatic coercion between byte and Unicode strings is desired.
unicode_escape		Produce a string that is suitable as Unicode literal in Python source code
unicode_internal		Return the internal representation of the operand

New in version 2.3: The idna and punycode encodings.

The following codecs provide str-to-str encoding and decoding 2 .

编解码器	别名	目的	Encoder/decoder
base64_codec	base64, base-64	Convert operand to multiline MIME base64 (the result always includes a trailing `'\n'` )	`base64.encodestring()` , `base64.decodestring()`
bz2_codec	bz2	使用 bz2 压缩操作数	`bz2.compress()` , `bz2.decompress()`
hex_codec	hex	Convert operand to hexadecimal representation, with two digits per byte	`binascii.b2a_hex()` , `binascii.a2b_hex()`
quopri_codec	quopri, quoted-printable, quotedprintable	Convert operand to MIME quoted printable	`quopri.encode()` with `quotetabs=True` , `quopri.decode()`
string_escape		Produce a string that is suitable as string literal in Python source code
uu_codec	uu	使用 uuencode 转换操作数	`uu.encode()` , `uu.decode()`
zlib_codec	zip, zlib	使用 gzip 压缩操作数	`zlib.compress()` , `zlib.decompress()`

1: str objects are also accepted as input in place of unicode objects. They are implicitly converted to unicode by decoding them using the default encoding. If this conversion fails, it may lead to encoding operations raising UnicodeDecodeError .
2 ( 1 , 2 ): unicode objects are also accepted as input in place of str objects. They are implicitly converted to str by encoding them using the default encoding. If this conversion fails, it may lead to decoding operations raising UnicodeEncodeError .

7.8.5. `encodings.idna` — 应用程序中的国际化域名 ¶

2.3 版新增。

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 .

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 Host 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 (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 httplib and ftplib , accept Unicode host names ( httplib then also transparently sends an IDNA hostname in the Host 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 .

7.8.6. `encodings.utf_8_sig` — 具有 BOM (字节序标记) 签名的 UTF-8 编解码器 ¶

2.5 版新增。

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). For decoding an optional UTF-8 encoded BOM at the start of the data will be skipped.

7.8. codecs — 编解码器注册和基类 ¶

7.8.1. 编解码器基类 ¶

7.8.1.1. Codec Objects ¶

7.8.1.2. IncrementalEncoder 对象 ¶

7.8.1.3. IncrementalDecoder 对象 ¶

7.8.1.4. StreamWriter 对象 ¶

7.8.1.5. StreamReader 对象 ¶

7.8.1.6. StreamReaderWriter 对象 ¶

7.8.1.7. StreamWriter 对象 ¶

7.8.2. 编码和 Unicode ¶

7.8.3. 标准编码 ¶

7.8.4. Python 特定编码 ¶

7.8.5. encodings.idna — 应用程序中的国际化域名 ¶

7.8.6. encodings.utf_8_sig — 具有 BOM (字节序标记) 签名的 UTF-8 编解码器 ¶

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7.8. `codecs` — 编解码器注册和基类 ¶

7.8.5. `encodings.idna` — 应用程序中的国际化域名 ¶

7.8.6. `encodings.utf_8_sig` — 具有 BOM (字节序标记) 签名的 UTF-8 编解码器 ¶