How to avoid the "ValueError: invalid \x escape" error in this special case?

Question

Obviously the wildcard %x is not recognized as a byte hex value, so I get the error "ValueError: invalid \x escape".

How to avoid this? I'm not familiar with python.

for i in xrange(0,length):

  if i % 2 == 0:

    tempArray.append(unpack("B",payload_raw[x])[0]^key)
    x += 1

  else:

    randomByte = random.randint(65,90)
    tempArray.append(randomByte)

    for i in range(0,len(tempArray)):

      tempArray[i]="\x%x"%tempArray[i]

    for i in range(0,len(tempArray),15):

      outArray.append("\n'"+"".join(tempArray[i:i+15])+"'")
      outArray = "".join(outArray)
      devide = "i % 2;"
      open_structure = open(structure).read()
      code = open_structure % (junkA,outArray,junkB,key,length,devide)
      b.write(code)
      b.flush()

Solution 1

chr() will give you the bytestring for a value between 0 and 255.

>>> chr(0xd3)
'\xd3'

Solution 2

Ignacio answer is the correct one, but there is also the Dark side of the Force:

>>> your_string = r'\x48\x65\x6c\x6c\x6f\x2c\x20\x57\x6f\x72\x6c\x64\x21'
>>> your_string.decode('string-escape')
'Hello, World!'

So you could have fixed your problem using a raw literal(r'\x' instead of '\x'), and converting the escapes into characters with the str.decode method.