I have the following function to parse a utf-8 string from a sequence of bytes
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]
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.
So far, I have the following:
def create_utf8(self, utf8_string):
return utf8_string.encode('utf-8')
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)
If possible, I'd like to adopt a structure for the code similar to the parse_utf8 example. What am I doing wrong?
Thank you for your help!
UPDATE: test driver, now correct
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
I get the following error:
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
In Python, a byte string is just that: a sequence of bytes. It isn't human-readable. Under the hood, everything must be converted to a byte string before it can be stored in a computer. On the other hand, a character string, often just called a "string", is a sequence of characters.
The encode() method is the most commonly used and recommended method to convert Python strings to bytes.
A string is composed of: An 8-byte object header (4-byte SyncBlock and a 4-byte type descriptor)
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÷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)) )
-- output --
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'>
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