How to format bytes from strings to hex values - python

I am reading in a binary file with big5 encoded characters. When I read a double byte sequence, they would appear as a list of bytes e.g.
>>> bytes = ['0xa6', '0x7b']
If I modify these string bytes:
>>> big5_str = ''
>>> for hexVal in bytes:
>>> newHexVal = '\\' + hexVal[1:]
>>> big5_str += newHexVal
so they appear as:
>>> print big5_str
>>> '\xa6\x7b'
but big5_str actually has the escape '\' still in the string:
>>> big5_str
>>> '\\xa6\\x7b'
and if i decode using big5, I only get the same string back (due to the double-backslash):
>>> print byte_string.decode('big5')
>>> '\xa6\x7b'
If I explicitly code the the byte sequence as the hex values:
>>> bytes2 = '\xa6\x7b'
>>> print bytes2.decode('big5')
>>> 州
My question is, how can I read these bytes, format them in '\x**' format them so that they are recognized as bytes, not strings, using a non-escaped backslash?

Related

Convert hex to decimal/string in python

So I wrote this small socket program to send a udp packet and receive the response
sock.sendto(data, (MCAST_GRP, MCAST_PORT))
msgFromServer = sock.recvfrom(1024)
banner=msgFromServer[0]
print(msgFromServer[0])
#name = msgFromServer[0].decode('ascii', 'ignore')
#print(name)
Response is
b'\xff\xff\xff\xffI\x11server banner\x00map\x00game\x00Counter-Strike: Global Offensive\x00\xda\x02\x00\x10\x00dl\x01\x011.38.2.2\x00\xa1\x87iempty,secure\x00\xda\x02\x00\x00\x00\x00\x00\x00'
Now the thing is I wanted to convert all hex value to decimal,
I tried the decode; but then I endup loosing all the hex values.
How can I convert all the hex values to decimal in my case
example: \x13 = 19
EDIT: I guess better way to iterate my question is
How do I convert only the hex values to decimal in the given response
There are two problems here:
handling the non-ASCII bytes
handling \xhh sequences which are legitimate characters in Python strings
We can address both with a mix of regular expressions and string methods.
First, decode the bytes to ASCII using the backslashreplace error handler to avoid losing the non-ASCII bytes.
>>> import re
>>>
>>> decoded = msgFromServer[0].decode('ascii', errors='backslashreplace')
>>> decoded
'\\xff\\xff\\xff\\xffI\x11server banner\x00map\x00game\x00Counter-Strike: Global Offensive\x00\\xda\x02\x00\x10\x00dl\x01\x011.38.2.2\x00\\xa1\\x87iempty,secure\x00\\xda\x02\x00\x00\x00\x00\x00\x00'
Next, use a regular expression to replace the non-ASCII '\\xhh' sequences with their numeric equivalents:
>>> temp = re.sub(r'\\x([a-fA-F0-9]{2})', lambda m: str(int(m.group(1), 16)), decoded)
>>> temp
'255255255255I\x11server banner\x00map\x00game\x00Counter-Strike: Global Offensive\x00218\x02\x00\x10\x00dl\x01\x011.38.2.2\x00161135iempty,secure\x00218\x02\x00\x00\x00\x00\x00\x00'
Finally, map \xhh escape sequences to their decimal values using str.translate:
>>> tt = str.maketrans({x: str(x) for x in range(32)})
>>> final = temp.translate(tt)
>>> final
'255255255255I17server banner0map0game0Counter-Strike: Global Offensive021820160dl111.38.2.20161135iempty,secure02182000000'
You can first convert the bytes representation to hex using the bytes.hex method and then cast it into an integer with the appropriate base with int(x, base)
>>> b'\x13'.hex()
'13'
>>> int(b'\x13'.hex(), 16)
19
Assume v contains the response, what you are asking for is
[int(i) for i in v]
I suspect it's not what you want, it is what I read from the question

How to programmatically retrieve the unicode char from hexademicals?

Given a list of hexadecimals that corresponds to the unicode, how to programmatically retrieve the unicode char?
E.g. Given the list:
>>> l = ['9359', '935A', '935B']
how to achieve this list:
>>> u = [u'\u9359', u'\u935A', u'\u935B']
>>> u
['鍙', '鍚', '鍛']
I've tried this but it throws a SyntaxError:
>>> u'\u' + l[0]
File "<stdin>", line 1
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 0-1: truncated \uXXXX escape
\uhhhh escapes are only valid in string literals, you can't use those to turn arbitrary hex values into characters. In other words, they are part of a larger syntax, and can't be used stand-alone.
Decode the hex value to an integer and pass it to the chr() function (or, on Python 2, the unichr() function):
[chr(int(v, 16)) for v in l] #
You could ask Python to interpret a string containing literal \uhhhh text as a Unicode string literal with the unicode_escape codec, but feels like overkill for individual codepoints:
[(b'\\u' + v.encode('ascii')).decode('unicode_escape') for v in l]
Note the double backslash in the prefix added, and that we have to create byte strings for this to work at all.
Demo:
>>> l = ['9359', '935A', '935B']
>>> [chr(int(v, 16)) for v in l]
['鍙', '鍚', '鍛']
>>> [(b'\\u' + v.encode('ascii')).decode('unicode_escape') for v in l]
['鍙', '鍚', '鍛']

How can I print unicode without using u'\uXXXX'

I'm trying to make a program to iterate through japanese characters (Python 2.7) and return/yield them in a printable format, but I cannot convert the hexadecimal numbers (3040-309f) into a format that can print the characters. I have found that using u'\u' works, but when I attempt to convert the numbers into that format using unicode('\u3040'), it is different from u'\u3040'. The code explains it better.
>>> s1 = u'\u309d'
>>> s2 = unicode("\u209d")
>>> print type(s1) == type(s2)
True
>>> print s1 == s2
False
>>> print s1, s2
ゝ \u209d
I have tried using UTF-8 and latin-1 for s2 as the second argument, but It does nothing. Also, I found that you can do u'\u{0}'.format(u'3040'), but I cannot make u'3040' in my iterator, and u'\u{0}'.format(unicode('3040') raises an error.
In byte string literals, the \uhhhh escape sequence is not interpreted, so you get a literal 6 characters instead.
Converting that to Unicode only decodes the string as ASCII data, not as a Python escape sequence.
You could decode from the unicode_escape encoding instead:
>>> "\u209d".decode('unicode_escape')
u'\u209d'
>>> print "\u209d".decode('unicode_escape')
₝
There are several downsides to this, however. Any other \ escape sequences also get decoded:
>>> '\\n'
'\\n'
>>> '\\n'.decode('unicode_escape')
u'\n'
so you may have to replace backslashes with doubled backslashes first to come back on top with those literal backslashes retained:
>>> '\\n'.replace('\\', '\\\\').decode('unicode_escape')
u'\\n'
But be very careful that you are not in fact trying to treat JSON data as Python string literals. JSON also uses the same escape sequence format but should instead be treated as JSON; decode with json.loads() instead:
>>> import json
>>> json.loads('"\u209d"')
u'\u209d'

Decode unicode string in python

I'd like to decode the following string:
t\u028c\u02c8m\u0251\u0279o\u028a\u032f
It should be the IPA of 'tomorrow' as given in a JSON string from http://rhymebrain.com/talk?function=getWordInfo&word=tomorrow
My understanding is that it should be something like:
x = 't\u028c\u02c8m\u0251\u0279o\u028a\u032f'
print x.decode()
I have tried the solutions from here , here , here, and here (and several other that more or less apply), and several permutations of its parts, but I can't get it to work.
Thank you
You need a u before your string (in Python 2.x, which you appear to be using) to indicate that this is a unicode string:
>>> x = u't\u028c\u02c8m\u0251\u0279o\u028a\u032f' # note the u
>>> print x
tʌˈmɑɹoʊ̯
If you have already stored the string in a variable, you can use the following constructor to convert the string into unicode:
>>> s = 't\u028c\u02c8m\u0251\u0279o\u028a\u032f' # your string has a unicode-escape encoding but is not unicode
>>> x = unicode(s, encoding='unicode-escape')
>>> print x
tʌˈmɑɹoʊ̯
>>> x
u't\u028c\u02c8m\u0251\u0279o\u028a\u032f' # a unicode string

Convert UTF-8 octets to unicode code points

I have a set of UTF-8 octets and I need to convert them back to unicode code points. How can I do this in python.
e.g. UTF-8 octet ['0xc5','0x81'] should be converted to 0x141 codepoint.
Python 3.x:
In Python 3.x, str is the class for Unicode text, and bytes is for containing octets.
If by "octets" you really mean strings in the form '0xc5' (rather than '\xc5') you can convert to bytes like this:
>>> bytes(int(x,0) for x in ['0xc5', '0x81'])
b'\xc5\x81'
You can then convert to str (ie: Unicode) using the str constructor...
>>> str(b'\xc5\x81', 'utf-8')
'Ł'
...or by calling .decode('utf-8') on the bytes object:
>>> b'\xc5\x81'.decode('utf-8')
'Ł'
>>> hex(ord('Ł'))
'0x141'
Pre-3.x:
Prior to 3.x, the str type was a byte array, and unicode was for Unicode text.
Again, if by "octets" you really mean strings in the form '0xc5' (rather than '\xc5') you can convert them like this:
>>> ''.join(chr(int(x,0)) for x in ['0xc5', '0x81'])
'\xc5\x81'
You can then convert to unicode using the constructor...
>>> unicode('\xc5\x81', 'utf-8')
u'\u0141'
...or by calling .decode('utf-8') on the str:
>>> '\xc5\x81'.decode('utf-8')
u'\u0141'
In lovely 3.x, where all strs are Unicode, and bytes are what strs used to be:
>>> s = str(bytes([0xc5, 0x81]), 'utf-8')
>>> s
'Ł'
>>> ord(s)
321
>>> hex(ord(s))
'0x141'
Which is what you asked for.
l = ['0xc5','0x81']
s = ''.join([chr(int(c, 16)) for c in l]).decode('utf8')
s
>>> u'\u0141'
>>> "".join((chr(int(x,16)) for x in ['0xc5','0x81'])).decode("utf8")
u'\u0141'

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