diff --git a/PrinterConnection.py b/PrinterConnection.py
index 28630dc0c5..a2021ca67d 100644
--- a/PrinterConnection.py
+++ b/PrinterConnection.py
@@ -149,8 +149,7 @@ class PrinterConnection(SignalEmitter):
     def updateFirmware(self, file_name):
         self._firmware_file_name = file_name
         self._update_firmware_thread.start()
-        
-    
+
     ##  Private connect function run by thread. Can be started by calling connect.
     def _connect(self): 
         self._is_connecting = True
@@ -378,6 +377,7 @@ class PrinterConnection(SignalEmitter):
                         self.sendCommand("M105 T%d" % self._temperature_requested_extruder_index)
                     else:
                         self.sendCommand("M105")
+
     ##  Send next Gcode in the gcode list            
     def _sendNextGcodeLine(self):
         if self._gcode_position >= len(self._gcode):
diff --git a/USBPrinterManager.py b/USBPrinterManager.py
index 8f2ba5e90a..300f6e7ef6 100644
--- a/USBPrinterManager.py
+++ b/USBPrinterManager.py
@@ -19,6 +19,7 @@ from UM.i18n import i18nCatalog
 
 i18n_catalog = i18nCatalog('plugins')
 
+
 class USBPrinterManager(QObject, SignalEmitter, Extension):
     def __init__(self, parent = None):
         super().__init__(parent)
@@ -48,26 +49,25 @@ class USBPrinterManager(QObject, SignalEmitter, Extension):
             self._firmware_view.show()
     
     
-    def spawnControlInterface(self,serial_port):
+    def spawnControlInterface(self, serial_port):
         if self._control_view is None:
             self._control_view = QQuickView()
             self._control_view.engine().rootContext().setContextProperty('manager',self)
             self._control_view.setSource(QUrl("plugins/USBPrinting/ControlWindow.qml"))
             self._control_view.show()
-            
-    
+
     processingProgress = pyqtSignal(float, arguments = ['amount'])
-    @pyqtProperty(float,notify = processingProgress)
+    @pyqtProperty(float, notify=processingProgress)
     def progress(self):
         return self._progress
-    
+
     pyqtExtruderTemperature = pyqtSignal(float, arguments = ['amount'])
-    @pyqtProperty(float,notify = pyqtExtruderTemperature)
+    @pyqtProperty(float, notify=pyqtExtruderTemperature)
     def extruderTemperature(self):
         return self._extruder_temp
     
     pyqtBedTemperature = pyqtSignal(float, arguments = ['amount'])
-    @pyqtProperty(float,notify = pyqtBedTemperature)
+    @pyqtProperty(float, notify=pyqtBedTemperature)
     def bedTemperature(self):
         return self._bed_temp
     
@@ -268,15 +268,15 @@ class USBPrinterManager(QObject, SignalEmitter, Extension):
                 i=0
                 while True:
                     values = winreg.EnumValue(key, i)
-                    if not base_list or 'USBSER' in values[0]:
-                        base_list+=[values[1]]
+                    if 'USBSER' in values[0]:
+                        base_list += [values[1]]
                     i+=1
             except:
                 pass
         
         if base_list:
             base_list = base_list + glob.glob('/dev/ttyUSB*') + glob.glob('/dev/ttyACM*') + glob.glob("/dev/cu.usb*")
-            base_list = filter(lambda s: not 'Bluetooth' in s, base_list) #Filter because mac sometimes puts them in the list
+            base_list = filter(lambda s: 'Bluetooth' not in s, base_list) #Filter because mac sometimes puts them in the list
             #prev = profile.getMachineSetting('serial_port_auto')
             #if prev in base_list:
             #    base_list.remove(prev)
diff --git a/avr_isp/ispBase.py b/avr_isp/ispBase.py
index bfed45f0ac..1ba1317f91 100644
--- a/avr_isp/ispBase.py
+++ b/avr_isp/ispBase.py
@@ -57,8 +57,10 @@ class IspBase():
         """
         raise IspError("Called undefined verifyFlash")
 
+
 class IspError(BaseException):
     def __init__(self, value):
         self.value = value
+
     def __str__(self):
         return repr(self.value)
diff --git a/avr_isp/stk500v2.py b/avr_isp/stk500v2.py
index 1af5416a40..c0e3b0ec89 100644
--- a/avr_isp/stk500v2.py
+++ b/avr_isp/stk500v2.py
@@ -3,7 +3,10 @@ STK500v2 protocol implementation for programming AVR chips.
 The STK500v2 protocol is used by the ArduinoMega2560 and a few other Arduino platforms to load firmware.
 This is a python 3 conversion of the code created by David Braam for the Cura project.
 """
-import os, struct, sys, time
+import os
+import struct
+import sys
+import time
 
 from serial import Serial
 from serial import SerialException
@@ -11,6 +14,7 @@ from serial import SerialTimeoutException
 
 from . import ispBase, intelHex
 
+
 class Stk500v2(ispBase.IspBase):
     def __init__(self):
         self.serial = None
@@ -55,8 +59,8 @@ class Stk500v2(ispBase.IspBase):
             self.serial.close()
             self.serial = None
 
-	#Leave ISP does not reset the serial port, only resets the device, and returns the serial port after disconnecting it from the programming interface.
-	#	This allows you to use the serial port without opening it again.
+    #Leave ISP does not reset the serial port, only resets the device, and returns the serial port after disconnecting it from the programming interface.
+    #	This allows you to use the serial port without opening it again.
     def leaveISP(self):
         if self.serial is not None:
             if self.sendMessage([0x11]) != [0x11, 0x00]: