extracted default plaform values to a method

hpib.py

@@ -22,16 +22,8 @@ class PrologixGpibUsb(PortDevice):
     def __init__(self, port="", timeout=1, portFormat="%d", maxDeviceNum=9, verbose=False,
                  findDevices=False):
         if port == "":
-            if platform.system() == "Linux":
-                port = "/dev/ttyUSB0"
-                portFormat = "%d"
-                maxDeviceNum = 99
-            elif platform.system() == "Darwin":
-                port = "/dev/ttys000"
-                portFormat = "%03d"
-                maxDeviceNum = 999
-            else:
-                raise NotImplementedError("Windows is not supported")
+            maxDeviceNum, port, portFormat = self._set_default_platform_values()
+
         if verbose:
             print "Looking for ports such as %s in range %d on %s" % \
                   ( port, maxDeviceNum, platform.system() )
@@ -73,6 +65,19 @@ class PrologixGpibUsb(PortDevice):
             self._devices = "Not scanned."
         self._hpib_address = -1
 
+    def _set_default_platform_values(self):
+        if platform.system() == "Linux":
+            port = "/dev/ttyUSB0"
+            port_format = "%d"
+            max_device_num = 99
+        elif platform.system() == "Darwin":
+            port = "/dev/ttys000"
+            port_format = "%03d"
+            max_device_num = 999
+        else:
+            raise NotImplementedError("Windows is not supported")
+        return max_device_num, port, port_format
+
     def command(self, hpib_address, command):
         if hpib_address != self._hpib_address:
             command = "++addr " + str(hpib_address) + chr(10) + command