Python: Seltsames Verhalten beim Schreiben von Binary

# -*- coding: utf-8 -*-

import sys

import os.path

import binascii

   #h_block_sum = "012345" #working example

   h_test = "bc000100000abc000100000a"  # writes bc000100000d0abc000100000d0a in file ???

   #h_block_sum = "bc000100001abc000100000a" # writes bc000100000abc000100000d0a in file ???

   hb=binascii.a2b_hex(h_test)

   try:

      outputfile = open('test.txt', 'w')

      outputfile.write(hb)

   finally:

      outputfile.close()

   # test content in python

   inputfile = open('test.txt', 'r')

   block = inputfile.read(20)

   str1 = ""

   for ch in block:

      str1 += hex(ord(ch))+" "

   print("Reading Test-Data: "+str1)

   inputfile.close()