simplify hex conversion code

rfid.py

@@ -127,7 +127,7 @@ def connect(ip, timeout=5, port=60000):
 
     @staticmethod
     def crc_16_ibm(data):
-        """Returns hex string with CRC values added to positions 4 through 8.
+        """Returns hex byte string with CRC values added to positions 4 through 8.
         This CRC value is required by the controller or it will not process the
         request.
 
@@ -156,7 +156,7 @@ def crc_16_ibm(data):
         endian = struct.pack("<H", code)
         data_list[4:8] = binascii.hexlify(endian).decode("utf8")
 
-        return "".join(data_list)
+        return bytearray.fromhex("".join(data_list))
 
     def add_user(self, badge, doors):
         if not isinstance(badge, int):
@@ -184,7 +184,6 @@ def add_user(self, badge, doors):
             + self.controller_serial
             + "00000200ffffffff"
         )
-        add_packet1 = bytearray.fromhex(add_packet1)
 
         self.s.send(self.start_transaction)
         self.s.send(add_packet1)
@@ -207,7 +206,6 @@ def add_user(self, badge, doors):
             + doors_enabled
             + "00000000"
         )
-        add_packet2 = bytearray.fromhex(add_packet2)
 
         self.s.send(self.start_transaction)
         self.s.send(add_packet2)
@@ -233,7 +231,6 @@ def remove_user(self, badge):
             + badge
             + "00000000204e460521149f3b0000000000000000"
         )
-        remove_packet = bytearray.fromhex(remove_packet)
 
         self.s.send(self.start_transaction)
         self.s.send(remove_packet)
@@ -260,7 +257,6 @@ def open_door(self, door_number):
             + door_number
             + "000000"
         )
-        open_door_packet = bytearray.fromhex(open_door_packet)
 
         self.s.send(self.start_transaction)
         self.s.send(open_door_packet)

tests.py

@@ -2,8 +2,7 @@
 
 from mock import patch
 
-from rfid import (RFIDClient, comma_format_to_ten_digit,
-                  ten_digit_to_comma_format)
+from rfid import RFIDClient, comma_format_to_ten_digit, ten_digit_to_comma_format
 
 TEST_CONTROLLER_IP = "192.168.1.20"
 TEST_CONTROLLER_SERIAL = 123106461
@@ -91,7 +90,10 @@ def test_crc_16_ibm(self):
             + "00000200ffffffff"
         )
         result = RFIDClient.crc_16_ibm(test_data)
-        expected_result = "201066f228000000000000009d74560700000200ffffffff"
+        expected_result = (
+            b" \x10f\xf2(\x00\x00\x00\x00\x00\x00\x00\x9dtV\x07\x00\x00\x02"
+            b"\x00\xff\xff\xff\xff"
+        )
         self.assertEqual(result, expected_result)
 
     @patch(