diff --git a/smartcard/Card.py b/smartcard/Card.py
index b82fad52..a261c744 100644
--- a/smartcard/Card.py
+++ b/smartcard/Card.py
@@ -21,7 +21,6 @@
 along with pyscard; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 """
-from smartcard.Exceptions import CardConnectionException, NoCardException
 from smartcard.reader.Reader import Reader
 from smartcard.System import readers
 from smartcard.util import toHexString
diff --git a/smartcard/CardConnection.py b/smartcard/CardConnection.py
index 607185e0..15bb52b2 100644
--- a/smartcard/CardConnection.py
+++ b/smartcard/CardConnection.py
@@ -24,8 +24,6 @@
 """
 
 from smartcard.CardConnectionEvent import CardConnectionEvent
-from smartcard.Exceptions import SmartcardException
-from smartcard.Observer import Observer
 from smartcard.Observer import Observable
 
 
diff --git a/smartcard/CardMonitoring.py b/smartcard/CardMonitoring.py
index e0273a93..30991e30 100644
--- a/smartcard/CardMonitoring.py
+++ b/smartcard/CardMonitoring.py
@@ -32,12 +32,9 @@
 from time import sleep
 import traceback
 
-from smartcard.System import readers
-from smartcard.Exceptions import CardRequestTimeoutException
 from smartcard.Observer import Observer
 from smartcard.Observer import Observable
 
-from smartcard.CardType import AnyCardType
 from smartcard.CardRequest import CardRequest
 
 _START_ON_DEMAND_ = False
@@ -216,7 +213,6 @@ def __getattr__(self, name):
 
 
 if __name__ == "__main__":
-    from smartcard.CardMonitoring import CardMonitor
     print 'insert or remove cards in the next 10 seconds'
 
     # a simple card observer that prints added/removed cards
diff --git a/smartcard/CardService.py b/smartcard/CardService.py
index b310f19a..0a2cf27a 100644
--- a/smartcard/CardService.py
+++ b/smartcard/CardService.py
@@ -30,7 +30,6 @@
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 """
 
-from smartcard.Exceptions import SmartcardException
 from smartcard.scard import *
 
 
diff --git a/smartcard/CardType.py b/smartcard/CardType.py
index 722a1cd1..d88ad047 100644
--- a/smartcard/CardType.py
+++ b/smartcard/CardType.py
@@ -21,6 +21,7 @@
 along with pyscard; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 """
+from smartcard.Exceptions import InvalidATRMaskLengthException
 from smartcard.System import readers
 from smartcard.util import toHexString
 
diff --git a/smartcard/ClassLoader.py b/smartcard/ClassLoader.py
index 3b232152..3cc59c56 100644
--- a/smartcard/ClassLoader.py
+++ b/smartcard/ClassLoader.py
@@ -9,10 +9,6 @@
 License: PSF license (http://docs.python.org/license.html).
 """
 
-import sys
-import types
-
-
 def get_mod(modulePath):
     """Import a module."""
     return __import__(modulePath, globals(), locals(), [''])
diff --git a/smartcard/ExclusiveConnectCardConnection.py b/smartcard/ExclusiveConnectCardConnection.py
index 8d1f0cbf..ee3524ce 100644
--- a/smartcard/ExclusiveConnectCardConnection.py
+++ b/smartcard/ExclusiveConnectCardConnection.py
@@ -21,7 +21,6 @@
 along with pyscard; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 """
-from smartcard.CardConnection import CardConnection
 from smartcard.CardConnectionDecorator import CardConnectionDecorator
 from smartcard.Exceptions import CardConnectionException
 from smartcard.scard import SCardConnect, SCardDisconnect
diff --git a/smartcard/ExclusiveTransmitCardConnection.py b/smartcard/ExclusiveTransmitCardConnection.py
index bbffa4da..ca836373 100644
--- a/smartcard/ExclusiveTransmitCardConnection.py
+++ b/smartcard/ExclusiveTransmitCardConnection.py
@@ -21,13 +21,11 @@
 along with pyscard; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 """
-from smartcard.CardConnection import CardConnection
 from smartcard.CardConnectionDecorator import CardConnectionDecorator
 from smartcard.Exceptions import CardConnectionException
 from smartcard.scard import SCardBeginTransaction, SCardEndTransaction
 from smartcard.scard import SCARD_LEAVE_CARD
 from smartcard.scard import SCardGetErrorMessage
-from smartcard.pcsc import PCSCCardConnection
 import smartcard.pcsc
 
 
diff --git a/smartcard/Observer.py b/smartcard/Observer.py
index b5f2b4ca..ce1d94fc 100644
--- a/smartcard/Observer.py
+++ b/smartcard/Observer.py
@@ -19,7 +19,7 @@
 
 class Observer(object):
 
-    def update(observable, arg):
+    def update(self, observable, arg):
         '''Called when the observed object is
         modified. You call an Observable object's
         notifyObservers method to notify all the
diff --git a/smartcard/PassThruCardService.py b/smartcard/PassThruCardService.py
index d22a48a3..25715354 100644
--- a/smartcard/PassThruCardService.py
+++ b/smartcard/PassThruCardService.py
@@ -53,7 +53,6 @@ def supports(cardname):
     SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
     DF_TELECOM = [0x7F, 0x10]
     from smartcard.System import readers
-    from smartcard.CardConnection import CardConnection
     cc = readers()[0].createConnection()
     cs = PassThruCardService(cc)
     cs.connection.connect()
diff --git a/smartcard/ReaderMonitoring.py b/smartcard/ReaderMonitoring.py
index 62aab450..cebcb07c 100644
--- a/smartcard/ReaderMonitoring.py
+++ b/smartcard/ReaderMonitoring.py
@@ -28,12 +28,11 @@
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 """
 
-from threading import Thread, Event, enumerate
+from threading import Thread, Event
 from time import sleep
 import traceback
 
 import smartcard.System
-from smartcard.Exceptions import ListReadersException
 from smartcard.Observer import Observer
 from smartcard.Observer import Observable
 from smartcard.Synchronization import *
@@ -196,7 +195,6 @@ def stop(self):
         self.join()
 
 if __name__ == "__main__":
-    from smartcard.ReaderMonitoring import ReaderMonitor
     print 'insert or remove readers in the next 20 seconds'
 
     # a simple reader observer that prints added/removed readers
diff --git a/smartcard/Session.py b/smartcard/Session.py
index a700eddb..78515999 100644
--- a/smartcard/Session.py
+++ b/smartcard/Session.py
@@ -24,7 +24,6 @@
 """
 
 from smartcard.Exceptions import InvalidReaderException, NoReadersException
-from smartcard.CardConnection import CardConnection
 from smartcard.PassThruCardService import PassThruCardService
 from smartcard.System import readers
 
@@ -110,8 +109,3 @@ def getATR(self):
     def __repr__(self):
         """Returns a string representation of the session."""
         return "<Session instance: readerName=%s>" % self.readerName
-
-
-if __name__ == '__main__':
-    """Small sample illustrating the use of Session.py."""
-    pass
diff --git a/smartcard/guid.py b/smartcard/guid.py
index c8715a72..497f25bf 100644
--- a/smartcard/guid.py
+++ b/smartcard/guid.py
@@ -60,7 +60,6 @@ def GUIDToStr(g):
 
 if __name__ == "__main__":
     """Small sample illustrating the use of guid.py."""
-    import smartcard.guid
     dummycardguid1 = strToGUID('{AD4F1667-EA75-4124-84D4-641B3B197C65}')
     print dummycardguid1
     print GUIDToStr(dummycardguid1)
diff --git a/smartcard/pcsc/PCSCCardConnection.py b/smartcard/pcsc/PCSCCardConnection.py
index 08ea84a9..fee3234b 100644
--- a/smartcard/pcsc/PCSCCardConnection.py
+++ b/smartcard/pcsc/PCSCCardConnection.py
@@ -25,7 +25,6 @@
 from smartcard.CardConnection import CardConnection
 from smartcard.Exceptions import (CardConnectionException,
     NoCardException, SmartcardException)
-from smartcard.Observer import Observable
 
 from smartcard.scard import *
 
@@ -240,8 +239,8 @@ def doGetAttrib(self, attribId):
     """Small sample illustrating the use of CardConnection."""
     SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
     DF_TELECOM = [0x7F, 0x10]
-    from smartcard.pcsc.PCSCReader import readers
-    cc = readers()[0].createConnection()
+    from smartcard.pcsc.PCSCReader import PCSCReader
+    cc = PCSCReader.readers()[0].createConnection()
     cc.connect()
     print "%r %x %x" % cc.transmit(SELECT + DF_TELECOM)
 
diff --git a/smartcard/pcsc/PCSCPart10.py b/smartcard/pcsc/PCSCPart10.py
index 927bc3a1..dbd99985 100644
--- a/smartcard/pcsc/PCSCPart10.py
+++ b/smartcard/pcsc/PCSCPart10.py
@@ -227,8 +227,8 @@ def getTlvProperties(cardConnection, featureList=None, controlCode=None):
 
 if __name__ == '__main__':
     """Small sample illustrating the use of PCSCPart10."""
-    from smartcard.pcsc.PCSCReader import readers
-    cc = readers()[0].createConnection()
+    from smartcard.pcsc.PCSCReader import PCSCReader
+    cc = PCSCReader.readers()[0].createConnection()
     cc.connect(mode=SCARD_SHARE_DIRECT)
 
     #print cc.control( CM_IOCTL_GET_FEATURE_REQUEST )
diff --git a/smartcard/pyro/PyroReader.py b/smartcard/pyro/PyroReader.py
index 7023cc89..a6fe396f 100644
--- a/smartcard/pyro/PyroReader.py
+++ b/smartcard/pyro/PyroReader.py
@@ -25,9 +25,8 @@
 import Pyro.core
 import Pyro.naming
 
-from smartcard.Exceptions import CardConnectionException, NoCardException
+from smartcard.Exceptions import NoCardException
 from smartcard.reader.Reader import Reader
-from smartcard.reader.ReaderFactory import ReaderFactory
 
 
 class PyroReader(Reader):
diff --git a/smartcard/pyro/server/PyroDaemon.py b/smartcard/pyro/server/PyroDaemon.py
index 89b5d1ae..90eac204 100644
--- a/smartcard/pyro/server/PyroDaemon.py
+++ b/smartcard/pyro/server/PyroDaemon.py
@@ -85,8 +85,8 @@ def __init__(self):
         Thread.__init__(self)
         self.setDaemon(True)
         self.setName('smartcard.pyro.server.PyroDaemonThread')
-        self.daemon = PyroDaemon()
+        self._daemon = PyroDaemon()
 
     def run(self):
         """Starts Pyro daemon."""
-        self.daemon.start()
+        self._daemon.start()
diff --git a/smartcard/pyro/server/PyroEventServer.py b/smartcard/pyro/server/PyroEventServer.py
index 90c4d998..2503e082 100644
--- a/smartcard/pyro/server/PyroEventServer.py
+++ b/smartcard/pyro/server/PyroEventServer.py
@@ -92,7 +92,6 @@ def __call__(self, signame, sf):
 
 
 if __name__ == '__main__':
-    import sys
     from smartcard.pyro.server.PyroNameServer import PyroNameServer
     pn = PyroNameServer(sys.argv[1:])
     pn.start()
diff --git a/smartcard/pyro/server/RemoteCardConnection.py b/smartcard/pyro/server/RemoteCardConnection.py
index 9df373ee..2b092b7c 100644
--- a/smartcard/pyro/server/RemoteCardConnection.py
+++ b/smartcard/pyro/server/RemoteCardConnection.py
@@ -26,10 +26,7 @@
 import Pyro.core
 import Pyro.naming
 
-from smartcard.CardConnection import CardConnection
 from smartcard.CardConnectionDecorator import CardConnectionDecorator
-from smartcard.Exceptions import CardConnectionException, NoCardException
-from smartcard.Observer import Observable
 
 
 class RemoteCardConnection(CardConnectionDecorator, Pyro.core.ObjBase):
diff --git a/smartcard/pyro/server/RemoteReaderServer.py b/smartcard/pyro/server/RemoteReaderServer.py
index f29096de..f3e715fe 100644
--- a/smartcard/pyro/server/RemoteReaderServer.py
+++ b/smartcard/pyro/server/RemoteReaderServer.py
@@ -32,10 +32,6 @@
     import sys
     sys.exit()
 
-import signal
-import time
-
-import smartcard.System
 from smartcard.reader.Reader import Reader
 from smartcard.ReaderMonitoring import ReaderMonitor, ReaderObserver
 from smartcard.pyro.server.RemoteCardConnection import RemoteCardConnection
diff --git a/smartcard/reader/ReaderGroups.py b/smartcard/reader/ReaderGroups.py
index 4e6cfbc1..64475944 100644
--- a/smartcard/reader/ReaderGroups.py
+++ b/smartcard/reader/ReaderGroups.py
@@ -67,9 +67,6 @@ def __onremoveitem__(self, item):
     def __iter__(self):
         return ulist.__iter__(self)
 
-    def next(self):
-        return ulist.__next__(self)
-
     #
     # abstract methods implemented in subclasses
     #
diff --git a/smartcard/sw/ErrorChecker.py b/smartcard/sw/ErrorChecker.py
index d29f0478..1296ff22 100644
--- a/smartcard/sw/ErrorChecker.py
+++ b/smartcard/sw/ErrorChecker.py
@@ -36,7 +36,7 @@ class ErrorChecker(object):
     pattern.
     """
 
-    def __call__(data, sw1, sw2):
+    def __call__(self, data, sw1, sw2):
         """Called to test data, sw1 and sw2 for error.
 
         @param data:       apdu response data
diff --git a/smartcard/util/__init__.py b/smartcard/util/__init__.py
index 2a8233a8..68fe0ba6 100644
--- a/smartcard/util/__init__.py
+++ b/smartcard/util/__init__.py
@@ -99,7 +99,7 @@ def toBytes(bytestring):
     """
     import struct
     import re
-    packedstring = ''.join(re.split('\W+', bytestring))
+    packedstring = ''.join(re.split(r'\W+', bytestring))
     try:
         return reduce(lambda x, y: x + [int(y, 16)],
                         struct.unpack('2s' * (len(packedstring) / 2),
@@ -204,9 +204,6 @@ def toHexString(bytes=[], format=0):
 
     from string import rstrip
 
-    for byte in tuple(bytes):
-        pass
-
     if type(bytes) is not list:
         raise TypeError('not a list of bytes')
 
diff --git a/smartcard/wx/APDUHexValidator.py b/smartcard/wx/APDUHexValidator.py
index dd090ddf..4e16ceb6 100644
--- a/smartcard/wx/APDUHexValidator.py
+++ b/smartcard/wx/APDUHexValidator.py
@@ -48,7 +48,7 @@ def Clone(self):
 
     def Validate(self, win):
         tc = self.GetWindow()
-        val = tc.GetValue()
+        value = tc.GetValue()
 
         if not apduregexp.match(value):
             return False
diff --git a/smartcard/wx/CardAndReaderTreePanel.py b/smartcard/wx/CardAndReaderTreePanel.py
index 0841ec1d..8106ef9f 100644
--- a/smartcard/wx/CardAndReaderTreePanel.py
+++ b/smartcard/wx/CardAndReaderTreePanel.py
@@ -408,9 +408,9 @@ def __init__(self, parent, appstyle, clientpanel):
     def OnDestroy(self, event):
         """Called on panel destruction."""
         # deregister observers
-        if hasattr(self, cardmonitor):
+        if hasattr(self, 'cardmonitor'):
             self.cardmonitor.deleteObserver(self.cardtreecardobserver)
-        if hasattr(self, readermonitor):
+        if hasattr(self, 'readermonitor'):
             self.readermonitor.deleteObserver(self.readertreereaderobserver)
             self.cardmonitor.deleteObserver(self.readertreecardobserver)
         event.Skip()
diff --git a/smartcard/wx/ReaderToolbar.py b/smartcard/wx/ReaderToolbar.py
index 946dfab0..fd353be8 100644
--- a/smartcard/wx/ReaderToolbar.py
+++ b/smartcard/wx/ReaderToolbar.py
@@ -77,12 +77,12 @@ def __init__(self, parent):
             bmpReader = wx.Bitmap(ICO_READER, wx.BITMAP_TYPE_ICO)
         else:
             bmpReader = wx.ArtProvider_GetBitmap(
-                wx.ART_HELP_BOOK, wx.ART_OTHER, isz)
+                wx.ART_HELP_BOOK, wx.ART_OTHER, tsize)
         if None != ICO_SMARTCARD:
             bmpCard = wx.Bitmap(ICO_SMARTCARD, wx.BITMAP_TYPE_ICO)
         else:
             bmpCard = wx.ArtProvider_GetBitmap(
-                wx.ART_HELP_BOOK, wx.ART_OTHER, isz)
+                wx.ART_HELP_BOOK, wx.ART_OTHER, tsize)
         self.readercombobox = ReaderComboBox(self)
 
         # create and add controls
diff --git a/smartcard/wx/SimpleSCardAppFrame.py b/smartcard/wx/SimpleSCardAppFrame.py
index cd5166cc..193c8a56 100644
--- a/smartcard/wx/SimpleSCardAppFrame.py
+++ b/smartcard/wx/SimpleSCardAppFrame.py
@@ -26,10 +26,11 @@
 
 import os.path
 import wx
+
 import smartcard.wx
-import APDUTracerPanel
-import CardAndReaderTreePanel
-import ReaderToolbar
+from smartcard.wx import APDUTracerPanel
+from smartcard.wx import CardAndReaderTreePanel
+from smartcard.wx import ReaderToolbar
 
 import smartcard
 from smartcard.wx.SimpleSCardAppEventObserver import \