Make compatible with python3

hpib.py

@@ -2,6 +2,7 @@ import serial
 import time
 import re
 import platform
+import sys
 
 
 class PortDevice(object):
@@ -69,14 +70,20 @@ class PrologixGpibUsb(PortDevice):
         if self._serialPort is None:
             raise serial.SerialException("Cannot find port")
 
+    def _write_serial(self, commandString):
+        if sys.version_info >= (3,0):
+            self._serialPort.write(bytes(commandString, 'utf-8'))
+        else:
+            self._serialPort.write(commandString)
+
     def _initialize_prologix_gpi(self):
-        self._serialPort.write("++savecfg 0" + chr(10))
-        self._serialPort.write("++auto 0" + chr(10))
-        self._serialPort.write("++eoi 1" + chr(10))
-        self._serialPort.write("++eos 2" + chr(10))
-        self._serialPort.write("++eot_enable 0" + chr(10))
-        self._serialPort.write("++eot_char 0" + chr(10))
-        self._serialPort.write("++read_tmo_ms 500" + chr(10))
+        self._write_serial("++savecfg 0" + chr(10))
+        self._write_serial("++auto 0" + chr(10))
+        self._write_serial("++eoi 1" + chr(10))
+        self._write_serial("++eos 2" + chr(10))
+        self._write_serial("++eot_enable 0" + chr(10))
+        self._write_serial("++eot_char 0" + chr(10))
+        self._write_serial("++read_tmo_ms 500" + chr(10))
 
     def _find_devices(self):
         self._devices = []
@@ -84,7 +91,7 @@ class PrologixGpibUsb(PortDevice):
             commandStr = "++addr " + str(address) + chr(10) + \
                          "*idn?" + chr(10) + \
                          "++read" + chr(10)
-            self._serialPort.write(commandStr)
+            self._write_serial(commandStr)
             returnStr = self._serialPort.readline()
             if returnStr != "":
                 self._devices += [address, returnStr]
@@ -94,7 +101,7 @@ class PrologixGpibUsb(PortDevice):
             command = "++addr " + str(hpib_address) + chr(10) + command
             self._hpib_address = hpib_address
 
-        self._serialPort.write(command + chr(10))
+        self._write_serial(command + chr(10))
 
     def query(self, hpib_address, query, count=80):
         if hpib_address != self._hpib_address:
@@ -102,13 +109,13 @@ class PrologixGpibUsb(PortDevice):
             self._hpib_address = hpib_address
 
         query += chr(10) + "++read eoi" + chr(10)
-        self._serialPort.write(query)
+        self._write_serial(query)
         line = self._serialPort.readline()
         return line[:-1]
 
     def set_local(self, hpib_address):
         # self._commandStr = "++addr "+str(hpib_address)+chr(10)+"loc "+str(hpib_address)+chr(10)
-        # self._commandCount = self._serialPort.write(self._commandStr)
+        # self._commandCount = self._write_serial(self._commandStr)
         return
 
     def get_devices(self):
@@ -126,22 +133,22 @@ class GPIB_232_485CT_A(PortDevice):
 
     def command(self, hpib_address, command):
         self._commandStr = "wr " + str(hpib_address) + chr(10) + command + chr(13)
-        self._commandCount = self._serialPort.write(self._commandStr)
+        self._commandCount = self._write_serial(self._commandStr)
 
     def query(self, hpib_address, query, count=80):
         # flushInput should not be necessary
         # self._serialPort.flushInput()
         self._commandStr = "wr " + str(hpib_address) + chr(10) + query + chr(13)
-        self._commandCount = self._serialPort.write(self._commandStr)
+        self._commandCount = self._write_serial(self._commandStr)
         self._queryStr = "rd #"+str(count)+" "+str(hpib_address)+chr(13)
-        self._queryCount = self._serialPort.write(self._queryStr)
+        self._queryCount = self._write_serial(self._queryStr)
         self._returnStr = self._serialPort.read(count)
         self._returnCnt = int(self._serialPort.readline())
         return self._returnStr[:self._returnCnt-1]
 
     def set_local(self, hpib_address):
         self._commandStr = "loc "+str(hpib_address)+chr(13)
-        self._commandCount = self._serialPort.write(self._commandStr)
+        self._commandCount = self._write_serial(self._commandStr)
 
 
 class HpibDevice(object):