diff --git a/bin/mn b/bin/mn
index df82b89..4c5cf3d 100755
--- a/bin/mn
+++ b/bin/mn
@@ -186,7 +186,8 @@ class MininetRunner( object ):
         for fileName in files:
             customs = {}
             if os.path.isfile( fileName ):
-                exec( compile ( open( fileName ).read(), fileName, 'exec' ),
+                # pylint: disable=exec-used
+                exec( compile( open( fileName ).read(), fileName, 'exec' ),
                       customs, customs )
                 for name, val in customs.items():
                     self.setCustom( name, val )
diff --git a/mininet/node.py b/mininet/node.py
index 1458428..8b6f8cf 100644
--- a/mininet/node.py
+++ b/mininet/node.py
@@ -89,7 +89,7 @@ class Node( object ):
         self.inNamespace = params.get( 'inNamespace', inNamespace )
 
         # Python 3 complains if we don't wait for shell exit
-        self.waitExited = params.get( 'waitExited', Python3==True )
+        self.waitExited = params.get( 'waitExited', Python3 == True )
 
         # Stash configuration parameters for future reference
         self.params = params
@@ -207,7 +207,7 @@ class Node( object ):
         # Leave this is as an instance method for now
         assert self
         popen = Popen( cmd, **params )
-        debug( '_popen', cmd,  popen.pid )
+        debug( '_popen', cmd, popen.pid )
         return popen
 
     def cleanup( self ):
@@ -732,7 +732,6 @@ class CPULimitedHost( Host ):
         super( CPULimitedHost, self ).cleanup()
         retry( retries=3, delaySecs=.1, fn=self.cgroupDel )
 
-
     _rtGroupSched = False   # internal class var: Is CONFIG_RT_GROUP_SCHED set?
 
     @classmethod
diff --git a/mininet/test/test_switchdpidassignment.py b/mininet/test/test_switchdpidassignment.py
index 2bd7a49..62ef493 100755
--- a/mininet/test/test_switchdpidassignment.py
+++ b/mininet/test/test_switchdpidassignment.py
@@ -35,7 +35,6 @@ class TestSwitchDpidAssignmentOVS( unittest.TestCase ):
         self.assertEqual( switch.defaultDpid(), switch.dpid )
         net.stop()
 
-
     def dpidFrom( self, num ):
         "Compute default dpid from number"
         fmt = ( '%0' + str( self.switchClass.dpidLen ) + 'x' )
@@ -50,7 +49,6 @@ class TestSwitchDpidAssignmentOVS( unittest.TestCase ):
         self.assertEqual( switch.dpid, dpid )
         net.stop()
 
-
     def testDefaultDpidAssignmentFailure( self ):
         """Verify that Default dpid assignment raises an Exception if the
         name of the switch does not contin a digit. Also verify the
diff --git a/mininet/util.py b/mininet/util.py
index 7397651..15a7b52 100644
--- a/mininet/util.py
+++ b/mininet/util.py
@@ -16,7 +16,7 @@ import sys
 
 # Python 2/3 compatibility
 Python3 = sys.version_info[0] == 3
-BaseString = str if Python3 else str.__base__
+BaseString = str if Python3 else getattr( str, '__base__' )
 Encoding = 'utf-8' if Python3 else None
 def decode( s ):
     "Decode a byte string if needed for Python 3"
@@ -26,17 +26,20 @@ def encode( s ):
     return s.encode( Encoding ) if Python3 else s
 try:
     import pexpect as oldpexpect
+
     class Pexpect( object ):
         "Custom pexpect that is compatible with str"
-        def spawn( self, *args, **kwargs):
+        @staticmethod
+        def spawn( *args, **kwargs):
             "pexpect.spawn that is compatible with str"
             if Python3 and 'encoding' not in kwargs:
                 kwargs.update( encoding='utf-8'  )
             return oldpexpect.spawn( *args, **kwargs )
+
         def __getattr__( self, name ):
             return getattr( oldpexpect, name )
     pexpect = Pexpect()
-except:
+except ImportError:
     pass
 
 
@@ -84,7 +87,7 @@ def oldQuietRun( *cmd ):
 # This is a bit complicated, but it enables us to
 # monitor command output as it is happening
 
-# pylint: disable=too-many-branches
+# pylint: disable=too-many-branches,too-many-statements
 def errRun( *cmd, **kwargs ):
     """Run a command and return stdout, stderr and return code
        cmd: string or list of command and args
@@ -415,11 +418,13 @@ def pmonitor(popens, timeoutms=500, readline=True,
             # Use non-blocking reads
             flags = fcntl( fd, F_GETFL )
             fcntl( fd, F_SETFL, flags | O_NONBLOCK )
+
     def readit( f ):
         "Helper function - read line or data"
         # Note this will block if readline is True
         line = f.readline() if readline else f.read( readmax )
         return decode( line )
+
     while popens:
         fds = poller.poll( timeoutms )
         if fds: