Unicode 指南

发布版本

1.12

本文介绍了 Python 对表示文本数据的 Unicode 规范的支持,并对各种 Unicode 常见使用问题做了解释。

Unicode 概述

定义

如今的程序需要能够处理各种各样的字符。应用程序通常做了国际化处理,用户可以选择不同的语言显示信息和输出数据。同一个程序可能需要以英语、法语、日语、希伯来语或俄语输出错误信息。网页内容可能由这些语言书写,并且可能包含不同的表情符号。Python 的字符串类型采用 Unicode 标准来表示字符,使得 Python 程序能够正常处理所有这些不同的字符。

Unicode 规范(https://www.unicode.org/)旨在罗列人类语言所用到的所有字符,并赋予每个字符唯一的编码。该规范一直在进行修订和更新,不断加入新的语种和符号。

一个 字符 是文本的最小组件。‘A’、‘B’、‘C’ 等都是不同的字符。‘È’ 和 ‘Í’ 也一样。字符会随着语言或者上下文的变化而变化。比如,‘Ⅰ’ 是一个表示 “罗马数字 1” 的字符,它与大写字母 ‘I’ 不同。他们往往看起来相同,但这是两个有着不同含义的字符。

Unicode 标准描述了字符是如何用 码位(code point) 表示的。码位的取值范围是 0 到 0x10FFFF 的整数(大约 110 万个值,实际分配的数字 没有那么多)。在 Unicode 标准和本文中,码位采用 U+265E 的形式,表示值为 0x265e 的字符(十进制为 9822)。

Unicode 标准中包含了许多表格,列出了很多字符及其对应的码位。

0061    'a'; LATIN SMALL LETTER A
0062    'b'; LATIN SMALL LETTER B
0063    'c'; LATIN SMALL LETTER C
...
007B    '{'; LEFT CURLY BRACKET
...
2167    'Ⅷ'; ROMAN NUMERAL EIGHT
2168    'Ⅸ'; ROMAN NUMERAL NINE
...
265E    '♞'; BLACK CHESS KNIGHT
265F    '♟'; BLACK CHESS PAWN
...
1F600   '😀'; GRINNING FACE
1F609   '😉'; WINKING FACE
...

严格地说,上述定义暗示了以下说法是没有意义的:“这是字符 U+265E”。U+265E 只是一个码位,代表某个特定的字符;这里它代表了字符 “国际象棋黑骑士” '♞'。在非正式的上下文中,有时会忽略码位和字符的区别。

一个字符在屏幕或纸上被表示为一组图形元素,被称为 字形(glyph) 。比如,大写字母 A 的字形,是两笔斜线和一笔横线,而具体的细节取决于所使用的字体。大部分 Python 代码不必担心字形,找到正确的显示字形通常是交给 GUI 工具包或终端的字体渲染程序来完成。

编码

上一段可以归结为:一个 Unicode 字符串是一系列码位(从 0 到 0x10FFFF 或者说十进制的 1,114,111 的数字)组成的序列。这一序列在内存中需被表示为一组 码元(code unit)码元 会映射成包含八个二进制位的字节。将 Unicode 字符串翻译成字节序列的规则称为 字符编码 ,或者 编码

大家首先会想到的编码可能是用 32 位的整数作为代码位,然后采用 CPU 对 32 位整数的表示法。字符串 “Python” 用这种表示法可能会如下所示:

   P           y           t           h           o           n
0x50 00 00 00 79 00 00 00 74 00 00 00 68 00 00 00 6f 00 00 00 6e 00 00 00
   0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

这种表示法非常直白,但也存在 一些问题。

  1. 不具可移植性;不同的处理器的字节序不同。

  2. 非常浪费空间。 在大多数文本中,大部分码位都小于 127 或 255,因此字节 0x00 占用了大量空间。相较于 ASCII 表示法所需的 6 个字节,以上字符串需要占用 24 个字节。RAM 用量的增加没那么要紧(台式计算机有成 GB 的 RAM,而字符串通常不会有那么大),但要把磁盘和网络带宽的用量增加 4 倍是无法忍受的。

  3. 与现有的 C 函数(如 strlen() )不兼容,因此需要采用一套新的宽字符串函数。

因此这种编码用得不多,人们转而选择其他更高效、更方便的编码,比如 UTF-8。

UTF-8 是最常用的编码之一,Python 往往默认会采用它。UTF 代表“Unicode Transformation Format”,'8' 表示编码采用 8 位数。(UTF-16 和 UTF-32 编码也是存在的,但其使用频率不如 UTF-8。)UTF-8 的规则如下:

  1. 如果码位 < 128,则直接用对应的字节值表示。

  2. 如果码位 >= 128,则转换为 2、3、4 个字节的序列,每个字节值都位于 128 和 255 之间。

UTF-8 有几个很方便的特性:

  1. 可以处理任何 Unicode 码位。

  2. Unicode 字符串被转换为一个字节序列,仅在表示空(null )字符(U+0000)时才会包含零值的字节。这意味着 strcpy() 之类的C 函数可以处理 UTF-8 字符串,而且用那些不能处理字符串结束符之外的零值字节的协议也能发送。

  3. ASCII 字符串也是也是也是合法的 UTF-8 文本。

  4. UTF-8 相当紧凑;大多数常用字符均可用一两个字节表示。

  5. 如果字节数据被损坏或丢失,则可以找出下一个 UTF-8 码点的开始位置并重新开始同步。随机的 8 位数据也不太可能像是有效的 UTF-8 编码。

  6. UTF-8 是一种面向字节的编码。编码规定了每个字符由一个或多个字节的序列表示。这避免了整数和双字节编码(如 UTF-16 和 UTF-32)可能出现的字节顺序问题,那时的字节序列会因执行编码的硬件而异。

引用文献

Unicode Consortium 站点 包含 Unicode 规范的字符图表、词汇表和 PDF 版本。请做好准备,有些内容读起来有点难度。该网站上还提供了 Unicode 起源和发展的`年表 <https://www.unicode.org/history/>`_ 。

在 Computerphile 的 Youtube 频道上,Tom Scott 简要地`讨论了 Unicode 和 UTF-8 <https://www.youtube.com/watch?v=MijmeoH9LT4>`_(9 分 36 秒)的历史。

为了帮助理解该标准,Jukka Korpela 编写了阅读 Unicode 字符表的`介绍性指南 <http://jkorpela.fi/unicode/guide.html>`_ 。

Joel Spolsky 撰写了另一篇不错的介绍性文章 <https://www.joelonsoftware.com/2003/10/08/the-absolute-minimum-every-software-developer-absolutely-positively-must-know-about-unicode-and-character- set-no-excuses/>`_ 。如果本文没让您弄清楚,那应在继续之前先试着读读这篇文章。

Wikipedia 条目通常也有帮助;请参阅“字符编码”和 UTF-8 的条目,例如:

Python's Unicode Support

现在您已经了解了 Unicode 的基础知识,可以看下 Python 的 Unicode 特性。

The String Type

从 Python 3.0 开始, str 类型包含了 Unicode 字符,这意味着用``"unicode rocks!"'unicode rocks!'`` 或三重引号字符串语法创建的任何字符串都会存储为 Unicode。

Python 源代码的默认编码是 UTF-8,因此可以直接在字符串中包含 Unicode 字符:

try:
    with open('/tmp/input.txt', 'r') as f:
        ...
except OSError:
    # 'File not found' error message.
    print("Fichier non trouvé")

旁注:Python 3 还支持在标识符中使用 Unicode 字符:

répertoire = "/tmp/records.log"
with open(répertoire, "w") as f:
    f.write("test\n")

如果无法在编辑器中输入某个字符,或出于某种原因想只保留 ASCII 编码的源代码,则还可以在字符串中使用转义序列。(根据系统的不同,可能会看到真的大写 Delta 字体而不是 u 转义符。):

>>> "\N{GREEK CAPITAL LETTER DELTA}"  # Using the character name
'\u0394'
>>> "\u0394"                          # Using a 16-bit hex value
'\u0394'
>>> "\U00000394"                      # Using a 32-bit hex value
'\u0394'

此外,可以用 bytesdecode() 方法创建一个字符串。 该方法可以接受 encoding 参数,比如可以为 UTF-8 ,以及可选的 errors 参数。

若无法根据编码规则对输入字符串进行编码,errors 参数指定了响应策略。 该参数的合法值可以是 'strict' (触发 UnicodeDecodeError 异常)、'replace' (用 U+FFFDREPLACEMENT CHARACTER)、'ignore' (只是将字符从 Unicode 结果中去掉),或 'backslashreplace' (插入一个 \xNN 转义序列)。 以下示例演示了这些不同的参数:

>>> b'\x80abc'.decode("utf-8", "strict")  
Traceback (most recent call last):
    ...
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 0:
  invalid start byte
>>> b'\x80abc'.decode("utf-8", "replace")
'\ufffdabc'
>>> b'\x80abc'.decode("utf-8", "backslashreplace")
'\\x80abc'
>>> b'\x80abc'.decode("utf-8", "ignore")
'abc'

编码格式以包含编码格式名称的字符串来指明。 Python 有大约 100 种不同的编码格式;清单详见 Python 库参考文档 标准编码。 一些编码格式有多个名称,比如 'latin-1''iso_8859_1''8859 都是指同一种编码。

利用内置函数 chr() 还可以创建单字符的 Unicode 字符串,该函数可接受整数参数,并返回包含对应码位的长度为 1 的 Unicode 字符串。内置函数 ord() 是其逆操作,参数为单个字符的 Unicode 字符串,并返回码位值:

>>> chr(57344)
'\ue000'
>>> ord('\ue000')
57344

Converting to Bytes

bytes.decode() 的逆方法是 str.encode() ,它会返回 Unicode 字符串的 bytes 形式,已按要求的 encoding 进行了编码。

参数 errors 的意义与 decode() 方法相同,但支持更多可能的handler。除了 'strict''ignore''replace' (这时会插入问号替换掉无法编码的字符),还有 'xmlcharrefreplace' (插入一个 XML 字符引用)、 backslashreplace (插入一个 \uNNNN 转义序列)和 namereplace (插入一个 \N{...} 转义序列 )。

以下例子演示了各种不同的结果:

>>> u = chr(40960) + 'abcd' + chr(1972)
>>> u.encode('utf-8')
b'\xea\x80\x80abcd\xde\xb4'
>>> u.encode('ascii')  
Traceback (most recent call last):
    ...
UnicodeEncodeError: 'ascii' codec can't encode character '\ua000' in
  position 0: ordinal not in range(128)
>>> u.encode('ascii', 'ignore')
b'abcd'
>>> u.encode('ascii', 'replace')
b'?abcd?'
>>> u.encode('ascii', 'xmlcharrefreplace')
b'&#40960;abcd&#1972;'
>>> u.encode('ascii', 'backslashreplace')
b'\\ua000abcd\\u07b4'
>>> u.encode('ascii', 'namereplace')
b'\\N{YI SYLLABLE IT}abcd\\u07b4'

用于注册和访问可用编码格式的底层函数,位于 codecs 模块中。 若要实现新的编码格式,则还需要了解 codecs 模块。 不过该模块返回的编码和解码函数通常更为底层一些,不大好用,编写新的编码格式是一项专业的任务,因此本文不会涉及该模块。

Python 源代码中的 Unicode 文字

在 Python 源代码中,可以用 \u 转义序列书写特定的 Unicode 码位,该序列后跟 4 个代表码位的十六进制数字。\U 转义序列用法类似,但要用8 个十六进制数字,而不是 4 个:

>>> s = "a\xac\u1234\u20ac\U00008000"
... #     ^^^^ two-digit hex escape
... #         ^^^^^^ four-digit Unicode escape
... #                     ^^^^^^^^^^ eight-digit Unicode escape
>>> [ord(c) for c in s]
[97, 172, 4660, 8364, 32768]

对大于 127 的码位使用转义序列,数量不多时没什么问题,但如果要用到很多重音字符,这会变得很烦人,类似于程序中的信息是用法语或其他使用重音的语言写的。也可以用内置函数 chr() 拼装字符串,但会更加乏味。

理想情况下,都希望能用母语的编码书写文本。还能用喜好的编辑器编辑 Python 源代码,编辑器要能自然地显示重音符,并在运行时使用正确的字符。

Python supports writing source code in UTF-8 by default, but you can use almost any encoding if you declare the encoding being used. This is done by including a special comment as either the first or second line of the source file:

#!/usr/bin/env python
# -*- coding: latin-1 -*-

u = 'abcdé'
print(ord(u[-1]))

The syntax is inspired by Emacs's notation for specifying variables local to a file. Emacs supports many different variables, but Python only supports 'coding'. The -*- symbols indicate to Emacs that the comment is special; they have no significance to Python but are a convention. Python looks for coding: name or coding=name in the comment.

If you don't include such a comment, the default encoding used will be UTF-8 as already mentioned. See also PEP 263 for more information.

Unicode Properties

The Unicode specification includes a database of information about code points. For each defined code point, the information includes the character's name, its category, the numeric value if applicable (for characters representing numeric concepts such as the Roman numerals, fractions such as one-third and four-fifths, etc.). There are also display-related properties, such as how to use the code point in bidirectional text.

The following program displays some information about several characters, and prints the numeric value of one particular character:

import unicodedata

u = chr(233) + chr(0x0bf2) + chr(3972) + chr(6000) + chr(13231)

for i, c in enumerate(u):
    print(i, '%04x' % ord(c), unicodedata.category(c), end=" ")
    print(unicodedata.name(c))

# Get numeric value of second character
print(unicodedata.numeric(u[1]))

When run, this prints:

0 00e9 Ll LATIN SMALL LETTER E WITH ACUTE
1 0bf2 No TAMIL NUMBER ONE THOUSAND
2 0f84 Mn TIBETAN MARK HALANTA
3 1770 Lo TAGBANWA LETTER SA
4 33af So SQUARE RAD OVER S SQUARED
1000.0

The category codes are abbreviations describing the nature of the character. These are grouped into categories such as "Letter", "Number", "Punctuation", or "Symbol", which in turn are broken up into subcategories. To take the codes from the above output, 'Ll' means 'Letter, lowercase', 'No' means "Number, other", 'Mn' is "Mark, nonspacing", and 'So' is "Symbol, other". See the General Category Values section of the Unicode Character Database documentation for a list of category codes.

Comparing Strings

Unicode adds some complication to comparing strings, because the same set of characters can be represented by different sequences of code points. For example, a letter like 'ê' can be represented as a single code point U+00EA, or as U+0065 U+0302, which is the code point for 'e' followed by a code point for 'COMBINING CIRCUMFLEX ACCENT'. These will produce the same output when printed, but one is a string of length 1 and the other is of length 2.

One tool for a case-insensitive comparison is the casefold() string method that converts a string to a case-insensitive form following an algorithm described by the Unicode Standard. This algorithm has special handling for characters such as the German letter 'ß' (code point U+00DF), which becomes the pair of lowercase letters 'ss'.

>>> street = 'Gürzenichstraße'
>>> street.casefold()
'gürzenichstrasse'

A second tool is the unicodedata module's normalize() function that converts strings to one of several normal forms, where letters followed by a combining character are replaced with single characters. normalize() can be used to perform string comparisons that won't falsely report inequality if two strings use combining characters differently:

import unicodedata

def compare_strs(s1, s2):
    def NFD(s):
        return unicodedata.normalize('NFD', s)

    return NFD(s1) == NFD(s2)

single_char = 'ê'
multiple_chars = '\N{LATIN SMALL LETTER E}\N{COMBINING CIRCUMFLEX ACCENT}'
print('length of first string=', len(single_char))
print('length of second string=', len(multiple_chars))
print(compare_strs(single_char, multiple_chars))

When run, this outputs:

$ python3 compare-strs.py
length of first string= 1
length of second string= 2
True

The first argument to the normalize() function is a string giving the desired normalization form, which can be one of 'NFC', 'NFKC', 'NFD', and 'NFKD'.

The Unicode Standard also specifies how to do caseless comparisons:

import unicodedata

def compare_caseless(s1, s2):
    def NFD(s):
        return unicodedata.normalize('NFD', s)

    return NFD(NFD(s1).casefold()) == NFD(NFD(s2).casefold())

# Example usage
single_char = 'ê'
multiple_chars = '\N{LATIN CAPITAL LETTER E}\N{COMBINING CIRCUMFLEX ACCENT}'

print(compare_caseless(single_char, multiple_chars))

This will print True. (Why is NFD() invoked twice? Because there are a few characters that make casefold() return a non-normalized string, so the result needs to be normalized again. See section 3.13 of the Unicode Standard for a discussion and an example.)

Unicode Regular Expressions

The regular expressions supported by the re module can be provided either as bytes or strings. Some of the special character sequences such as \d and \w have different meanings depending on whether the pattern is supplied as bytes or a string. For example, \d will match the characters [0-9] in bytes but in strings will match any character that's in the 'Nd' category.

The string in this example has the number 57 written in both Thai and Arabic numerals:

import re
p = re.compile(r'\d+')

s = "Over \u0e55\u0e57 57 flavours"
m = p.search(s)
print(repr(m.group()))

When executed, \d+ will match the Thai numerals and print them out. If you supply the re.ASCII flag to compile(), \d+ will match the substring "57" instead.

Similarly, \w matches a wide variety of Unicode characters but only [a-zA-Z0-9_] in bytes or if re.ASCII is supplied, and \s will match either Unicode whitespace characters or [ \t\n\r\f\v].

引用文献

Some good alternative discussions of Python's Unicode support are:

The str type is described in the Python library reference at 文本序列类型 --- str.

The documentation for the unicodedata module.

The documentation for the codecs module.

Marc-André Lemburg gave a presentation titled "Python and Unicode" (PDF slides) at EuroPython 2002. The slides are an excellent overview of the design of Python 2's Unicode features (where the Unicode string type is called unicode and literals start with u).

Reading and Writing Unicode Data

Once you've written some code that works with Unicode data, the next problem is input/output. How do you get Unicode strings into your program, and how do you convert Unicode into a form suitable for storage or transmission?

It's possible that you may not need to do anything depending on your input sources and output destinations; you should check whether the libraries used in your application support Unicode natively. XML parsers often return Unicode data, for example. Many relational databases also support Unicode-valued columns and can return Unicode values from an SQL query.

Unicode data is usually converted to a particular encoding before it gets written to disk or sent over a socket. It's possible to do all the work yourself: open a file, read an 8-bit bytes object from it, and convert the bytes with bytes.decode(encoding). However, the manual approach is not recommended.

One problem is the multi-byte nature of encodings; one Unicode character can be represented by several bytes. If you want to read the file in arbitrary-sized chunks (say, 1024 or 4096 bytes), you need to write error-handling code to catch the case where only part of the bytes encoding a single Unicode character are read at the end of a chunk. One solution would be to read the entire file into memory and then perform the decoding, but that prevents you from working with files that are extremely large; if you need to read a 2 GiB file, you need 2 GiB of RAM. (More, really, since for at least a moment you'd need to have both the encoded string and its Unicode version in memory.)

The solution would be to use the low-level decoding interface to catch the case of partial coding sequences. The work of implementing this has already been done for you: the built-in open() function can return a file-like object that assumes the file's contents are in a specified encoding and accepts Unicode parameters for methods such as read() and write(). This works through open()'s encoding and errors parameters which are interpreted just like those in str.encode() and bytes.decode().

Reading Unicode from a file is therefore simple:

with open('unicode.txt', encoding='utf-8') as f:
    for line in f:
        print(repr(line))

It's also possible to open files in update mode, allowing both reading and writing:

with open('test', encoding='utf-8', mode='w+') as f:
    f.write('\u4500 blah blah blah\n')
    f.seek(0)
    print(repr(f.readline()[:1]))

The Unicode character U+FEFF is used as a byte-order mark (BOM), and is often written as the first character of a file in order to assist with autodetection of the file's byte ordering. Some encodings, such as UTF-16, expect a BOM to be present at the start of a file; when such an encoding is used, the BOM will be automatically written as the first character and will be silently dropped when the file is read. There are variants of these encodings, such as 'utf-16-le' and 'utf-16-be' for little-endian and big-endian encodings, that specify one particular byte ordering and don't skip the BOM.

In some areas, it is also convention to use a "BOM" at the start of UTF-8 encoded files; the name is misleading since UTF-8 is not byte-order dependent. The mark simply announces that the file is encoded in UTF-8. For reading such files, use the 'utf-8-sig' codec to automatically skip the mark if present.

Unicode filenames

Most of the operating systems in common use today support filenames that contain arbitrary Unicode characters. Usually this is implemented by converting the Unicode string into some encoding that varies depending on the system. Today Python is converging on using UTF-8: Python on MacOS has used UTF-8 for several versions, and Python 3.6 switched to using UTF-8 on Windows as well. On Unix systems, there will only be a filesystem encoding if you've set the LANG or LC_CTYPE environment variables; if you haven't, the default encoding is again UTF-8.

The sys.getfilesystemencoding() function returns the encoding to use on your current system, in case you want to do the encoding manually, but there's not much reason to bother. When opening a file for reading or writing, you can usually just provide the Unicode string as the filename, and it will be automatically converted to the right encoding for you:

filename = 'filename\u4500abc'
with open(filename, 'w') as f:
    f.write('blah\n')

Functions in the os module such as os.stat() will also accept Unicode filenames.

The os.listdir() function returns filenames, which raises an issue: should it return the Unicode version of filenames, or should it return bytes containing the encoded versions? os.listdir() can do both, depending on whether you provided the directory path as bytes or a Unicode string. If you pass a Unicode string as the path, filenames will be decoded using the filesystem's encoding and a list of Unicode strings will be returned, while passing a byte path will return the filenames as bytes. For example, assuming the default filesystem encoding is UTF-8, running the following program:

fn = 'filename\u4500abc'
f = open(fn, 'w')
f.close()

import os
print(os.listdir(b'.'))
print(os.listdir('.'))

will produce the following output:

$ python listdir-test.py
[b'filename\xe4\x94\x80abc', ...]
['filename\u4500abc', ...]

The first list contains UTF-8-encoded filenames, and the second list contains the Unicode versions.

Note that on most occasions, you should can just stick with using Unicode with these APIs. The bytes APIs should only be used on systems where undecodable file names can be present; that's pretty much only Unix systems now.

Tips for Writing Unicode-aware Programs

This section provides some suggestions on writing software that deals with Unicode.

The most important tip is:

Software should only work with Unicode strings internally, decoding the input data as soon as possible and encoding the output only at the end.

If you attempt to write processing functions that accept both Unicode and byte strings, you will find your program vulnerable to bugs wherever you combine the two different kinds of strings. There is no automatic encoding or decoding: if you do e.g. str + bytes, a TypeError will be raised.

When using data coming from a web browser or some other untrusted source, a common technique is to check for illegal characters in a string before using the string in a generated command line or storing it in a database. If you're doing this, be careful to check the decoded string, not the encoded bytes data; some encodings may have interesting properties, such as not being bijective or not being fully ASCII-compatible. This is especially true if the input data also specifies the encoding, since the attacker can then choose a clever way to hide malicious text in the encoded bytestream.

Converting Between File Encodings

The StreamRecoder class can transparently convert between encodings, taking a stream that returns data in encoding #1 and behaving like a stream returning data in encoding #2.

For example, if you have an input file f that's in Latin-1, you can wrap it with a StreamRecoder to return bytes encoded in UTF-8:

new_f = codecs.StreamRecoder(f,
    # en/decoder: used by read() to encode its results and
    # by write() to decode its input.
    codecs.getencoder('utf-8'), codecs.getdecoder('utf-8'),

    # reader/writer: used to read and write to the stream.
    codecs.getreader('latin-1'), codecs.getwriter('latin-1') )

Files in an Unknown Encoding

What can you do if you need to make a change to a file, but don't know the file's encoding? If you know the encoding is ASCII-compatible and only want to examine or modify the ASCII parts, you can open the file with the surrogateescape error handler:

with open(fname, 'r', encoding="ascii", errors="surrogateescape") as f:
    data = f.read()

# make changes to the string 'data'

with open(fname + '.new', 'w',
          encoding="ascii", errors="surrogateescape") as f:
    f.write(data)

The surrogateescape error handler will decode any non-ASCII bytes as code points in a special range running from U+DC80 to U+DCFF. These code points will then turn back into the same bytes when the surrogateescape error handler is used to encode the data and write it back out.

引用文献

One section of Mastering Python 3 Input/Output, a PyCon 2010 talk by David Beazley, discusses text processing and binary data handling.

The PDF slides for Marc-André Lemburg's presentation "Writing Unicode-aware Applications in Python" discuss questions of character encodings as well as how to internationalize and localize an application. These slides cover Python 2.x only.

The Guts of Unicode in Python is a PyCon 2013 talk by Benjamin Peterson that discusses the internal Unicode representation in Python 3.3.

致谢

The initial draft of this document was written by Andrew Kuchling. It has since been revised further by Alexander Belopolsky, Georg Brandl, Andrew Kuchling, and Ezio Melotti.

Thanks to the following people who have noted errors or offered suggestions on this article: Éric Araujo, Nicholas Bastin, Nick Coghlan, Marius Gedminas, Kent Johnson, Ken Krugler, Marc-André Lemburg, Martin von Löwis, Terry J. Reedy, Serhiy Storchaka, Eryk Sun, Chad Whitacre, Graham Wideman.