Python:将utf-8字符串转换为字节字符串

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问题描述

我具有以下功能，可从字节序列中解析utf-8字符串

I have the following function to parse a utf-8 string from a sequence of bytes

注意-'length_size'是表示utf-8字符串长度的字节数

Note -- 'length_size' is the number of bytes it take to represent the length of the utf-8 string

def parse_utf8(self, bytes, length_size):

    length = bytes2int(bytes[0:length_size])
    value = ''.join(['%c' % b for b in bytes[length_size:length_size+length]])
    return value


def bytes2int(raw_bytes, signed=False):
    """
    Convert a string of bytes to an integer (assumes little-endian byte order)
    """
    if len(raw_bytes) == 0:
        return None
    fmt = {1:'B', 2:'H', 4:'I', 8:'Q'}[len(raw_bytes)]
    if signed:
        fmt = fmt.lower()
    return struct.unpack('<'+fmt, raw_bytes)[0]

我想反写该函数-即一个将采用utf-8编码的字符串并将其表示形式返回为字节字符串的函数.

I'd like to write the function in reverse -- i.e. a function that will take a utf-8 encoded string and return it's representation as a byte string.

到目前为止，我有以下内容:

So far, I have the following:

def create_utf8(self, utf8_string):
    return utf8_string.encode('utf-8')

尝试对其进行测试时遇到以下错误:

I run into the following error when attempting to test it:

  File "writer.py", line 229, in create_utf8
return utf8_string.encode('utf-8')
UnicodeDecodeError: 'ascii' codec can't decode byte 0x98 in position 0: ordinal not in range(128)

如果可能的话，我想为代码采用类似于parse_utf8示例的结构.我在做什么错了?

If possible, I'd like to adopt a structure for the code similar to the parse_utf8 example. What am I doing wrong?

谢谢您的帮助！

更新:测试驱动程序，现在正确了

def random_utf8_seq(self, length):
    # from http://www.w3.org/2001/06/utf-8-test/postscript-utf-8.html
    test_charset = u" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ ¡¢£¤¥¦§¨©ª«¬ ®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿĂăĄąĆćČčĎďĐđĘęĚěĹĺĽľŁłŃńŇňŐőŒœŔŕŘřŚśŞşŠšŢţŤťŮůŰűŸŹźŻżŽžƒˆˇ˘˙˛˜˝–—‘’‚""„†‡•…‰‹›€™"

    utf8_seq = u""

    for i in range(length):
        utf8_seq += random.choice(test_charset)

    return utf8_seq

我收到以下错误:

input_str = self.random_utf8_seq(200)
  File "writer.py", line 226, in random_utf8_seq
print unicode(utf8_seq, "utf-8")
  UnicodeDecodeError: 'utf8' codec can't decode byte 0xbb in position 0: invalid start byte

推荐答案

如果要使用utf-8 =>字节串转换，则可以使用 str.encode ，但首先需要在示例中正确标记源字符串的类型-带有 u 的unicode前缀:

If utf-8 => bytestring conversion is what do you want then you may use str.encode, but first you need to properly mark the type of source string in your example - prefix with u for unicode:

# coding: utf-8
import random

    def random_utf8_seq(length):
        # from http://www.w3.org/2001/06/utf-8-test/postscript-utf-8.html
        test_charset = u" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ ¡¢£¤¥¦§¨©ª«¬ ®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿĂăĄąĆćČčĎďĐđĘęĚěĹĺĽľŁłŃńŇňŐőŒœŔŕŘřŚśŞşŠšŢţŤťŮůŰűŸŹźŻżŽžƒˆˇ˘˙˛˜˝–—‘’‚""„†‡•…‰‹›€™"

        utf8_seq = u''

        for i in range(length):
            utf8_seq += random.choice(test_charset)

        print utf8_seq.encode('utf-8')
        return utf8_seq.encode('utf-8')

    print( type(random_utf8_seq(200)) )

-输出-

õ3×sÔP{Ć.s(Ë°˙ě÷xÓ@bűV—û´ő¢uZÓČn˜0|_"Ðyø`êš·ÏÝhunÍÅ=ä?
óP{tlÇűpb¸7s´ňƒG—čøň\zčłŢXÂYqLĆúěă(ÿî ¥PyÐÔŇn×œ¦Ì˝+•ì›
ŻÛ°Ñ^ÝC÷ŢŐIñJĹţÒył"MťÆ‹ČČ4þ!»šåŮ@Öhň-
ÈLGĄ¢ß˛Đ¯.ªÆź˘Ř^ĽÛŹËaĂŕ¹#¢éüÜńlÊqš=VřU…‚–MŽÎÉèoÙŹŠ¨Ð
<type 'str'>

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