Not able to convert HEX to ASCII in python 3.6.3

Question

I tried below methods, but no luck.

method 1:

var contains the hex value

bytes.fromhex(var).decode('ascii')
Traceback (most recent call last): File "<stdin>", line 1, in <module> UnicodeDecodeError: 'ascii' codec can't decode byte 0xdb in position 0: ordinal not in range(128)

method 2:

codecs.decode(var,"hex")

This is returning me in bytes, not in ASCII.

Can someone help on this conversion?

Answer 1

Did you try:

chr(var)

This should give you the character for an ASCII code.

Answer 2

As it follows from the question I assume using Python 3x.

The reason of your error is the fact, that you try to decode with ASCII the byte '0xdb' which has the value above 127.
You just can't do that - there is no such a byte value in ASCII encoding.

Your options are:

1. Ignore decode errors:

>>> u = 'DB91132598CC' # unicode
>>> b = codecs.decode(u,"hex") # bytes
>>> b
b'\xdb\x91\x13%\x98\xcc'
>>> result = b.decode("ascii", errors="ignore") # unicode
>>> result
'\x13%'

2. Use different encoding:

>>> result = b.decode("cp1252") # for example 
>>> result
'Û‘\x13%˜Ì'

If you want only ASCII chars in the result use option #1.

Answer 3

>>> var = int('7A', 16) #var is an integer now
>>> chr(var) #int value to char
'z'

This solution is only for one character. You have to split the string and convert all hex values seperated. Look here how to split it.

Answer 4

have you tried

 codecs.decode(codecs.decode(var,'hex'),'ascii')

Answer 5

The following code:

codecs.decode(var,"hex")

in Python 2.7 results with str:

'\xdb\x91\x13%\x98\xcc\xbfv\xaef\x8bK\x08Qv\xbb\x19\'u"\x1f\xdb\xb5\x0f\xce\x1c9\'\xc0w\xea\xf1\xe3\xda\xc4\xc8\xa8\xe8\x02\x8c?r\x95\xef\x81W\xce\xd5\x97\xa3n\xf1\xc3\xbf\xa4QG{\xff2\xee\xb1\x80l,\xc0D%\x85\x19z+\xcd,C\x92\x14z\xad\xb90f\xd0\xbaZ\xb6\xdb\xfd?o\xce\xb7\x07:\xe6\x1a]J\xa8\xab\xcb\xcf\xf4\xee\xbd\x1a\x16Uh\x9b\xfd~\xab\x82\xd7{\xf7"Ou\xfb\xcd2<\x9b\x9f\xa9\xc0\xb7\xd7\x99\x18\x08x\xa8\x1d]\x07\xcf\x05\xbe9\xee\xf9\x89\xb2\xfc0w\x99},/\x11b\xe5\xb4}\x99\xe4\xb4\x15\xbc\x8c\xe5\xc7UGi1\xbd\x8e\xd1K_\xce\xc1\xc8\xc6TQYF\xabx`\xbb\xbe\xe7\xdc\xcf\xda\xa7\xaaA\x0f\xf6SR\xb1S\xb5\x87(\xd5x\x14\xc6\x10\xf8%(m\x83\x0c0\x84)\xbd\xcf\x11g\x88{\x12^\xfb/\xa3K=\xea\xcd2\x9fWgL\x07\x1b\xefl\x9c\xea\xc0\xc7\xfa\xbbXz\x1do\x8bM\x0bS'

and in Python 3.6 bytes:

b'\xdb\x91\x13%\x98\xcc\xbfv\xaef\x8bK\x08Qv\xbb\x19\'u"\x1f\xdb\xb5\x0f\xce\x1c9\'\xc0w\xea\xf1\xe3\xda\xc4\xc8\xa8\xe8\x02\x8c?r\x95\xef\x81W\xce\xd5\x97\xa3n\xf1\xc3\xbf\xa4QG{\xff2\xee\xb1\x80l,\xc0D%\x85\x19z+\xcd,C\x92\x14z\xad\xb90f\xd0\xbaZ\xb6\xdb\xfd?o\xce\xb7\x07:\xe6\x1a]J\xa8\xab\xcb\xcf\xf4\xee\xbd\x1a\x16Uh\x9b\xfd~\xab\x82\xd7{\xf7"Ou\xfb\xcd2<\x9b\x9f\xa9\xc0\xb7\xd7\x99\x18\x08x\xa8\x1d]\x07\xcf\x05\xbe9\xee\xf9\x89\xb2\xfc0w\x99},/\x11b\xe5\xb4}\x99\xe4\xb4\x15\xbc\x8c\xe5\xc7UGi1\xbd\x8e\xd1K_\xce\xc1\xc8\xc6TQYF\xabx`\xbb\xbe\xe7\xdc\xcf\xda\xa7\xaaA\x0f\xf6SR\xb1S\xb5\x87(\xd5x\x14\xc6\x10\xf8%(m\x83\x0c0\x84)\xbd\xcf\x11g\x88{\x12^\xfb/\xa3K=\xea\xcd2\x9fWgL\x07\x1b\xefl\x9c\xea\xc0\xc7\xfa\xbbXz\x1do\x8bM\x0bS'

The reason is that in Python 2.7

str == bytes #True

while in Python 3.6

str == bytes #False

Python 2 strings are byte strings, while Python 3 strings are unicode strings. Both results are actually the same, but byte string in Python 3 is of type bytes not str and literal representation is prefixed with b.
This has nothing to do with ASCII encoding as none of the output variables (regardless of Python version) is ASCII encoded.
Moreover on Python 2.7 you will also get this error:

codecs.decode(var, 'hex').decode('ascii')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xdb in position 0: ordinal not in range(128)

I actually pasted it from Python 2.7 interpreter but you can check yourself.
Your output string can't be decoded with ascii codec in any version of Python because it's simply not ascii encoded string in any case.