Python：將utf-8字符串轉換為字節字符串

Question

我有以下函數來解析字節序列中的utf-8字符串

注 - 'length_size'是表示utf-8字符串長度所需的字節數

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]

我想反向編寫函數 - 即一個函數將采用utf-8編碼的字符串並將其表示作為字節字符串返回。

到目前為止，我有以下內容：

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

嘗試測試時遇到以下錯誤：

  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)

如果可能的話，我想采用類似於parse_utf8示例的代碼結構。 我究竟做錯了什么？

謝謝您的幫助！

更新：測試驅動程序，現在正確

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÷øùúûüýþÿĂ㥹ĆćČčĎďĐđĘęĚěĹ弾ŁłŃńŇňŐőŒœŔŕŘřŚśŞşŠšŢţŤťŮůŰűŸŹźŻżŽžƒˆˇ˘˙˛˜˝–—‘’‚“”„†‡•…‰‹›€™"

    utf8_seq = u""

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

    return utf8_seq

我收到以下錯誤：

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

Answer 1

如果您想要utf-8 => bytestring轉換，那么您可以使用str.encode ，但首先需要在示例中正確標記源字符串的類型 - 使用u作為unicode的前綴：

# 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÷øùúûüýþÿĂ㥹ĆćČčĎďĐđĘęĚěĹ弾ŁłŃńŇňŐőŒœŔŕŘřŚśŞşŠšŢţŤťŮůŰűŸŹźŻżŽžƒˆˇ˘˙˛˜˝–—‘’‚“”„†‡•…‰‹›€™"

        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)) )

- 輸出 -

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