diff --git a/copycat/__init__.py b/copycat/__init__.py
index ae36718..fc24510 100644
--- a/copycat/__init__.py
+++ b/copycat/__init__.py
@@ -1 +1 @@
-from copycat import Copycat
+from copycat import Copycat  # noqa
diff --git a/copycat/bond.py b/copycat/bond.py
index 456aff6..ff57fa6 100644
--- a/copycat/bond.py
+++ b/copycat/bond.py
@@ -30,17 +30,20 @@ class Bond(WorkspaceStructure):
 
     def flippedVersion(self):
         slipnet = self.ctx.slipnet
-        return Bond(self.ctx,
+        return Bond(
+            self.ctx,
             self.destination, self.source,
             self.category.getRelatedNode(slipnet.opposite),
-            self.facet, self.destinationDescriptor, self.sourceDescriptor)
+            self.facet, self.destinationDescriptor, self.sourceDescriptor
+        )
 
     def __repr__(self):
         return '<Bond: %s>' % self.__str__()
 
     def __str__(self):
         return '%s bond between %s and %s' % (
-            self.category.name, self.leftObject, self.rightObject)
+            self.category.name, self.leftObject, self.rightObject,
+        )
 
     def buildBond(self):
         workspace = self.ctx.workspace
@@ -82,9 +85,10 @@ class Bond(WorkspaceStructure):
             else:
                 objekt = self.leftObject.correspondence.objectFromInitial
             if objekt.leftmost and objekt.rightBond:
-                if  (objekt.rightBond.directionCategory and
-                     objekt.rightBond.directionCategory !=
-                     self.directionCategory):
+                if (
+                    objekt.rightBond.directionCategory and
+                    objekt.rightBond.directionCategory != self.directionCategory
+                ):
                     incompatibles += [correspondence]
         if self.rightObject.rightmost and self.rightObject.correspondence:
             correspondence = self.rightObject.correspondence
@@ -93,9 +97,10 @@ class Bond(WorkspaceStructure):
             else:
                 objekt = self.rightObject.correspondence.objectFromInitial
             if objekt.rightmost and objekt.leftBond:
-                if  (objekt.leftBond.directionCategory and
-                     objekt.leftBond.directionCategory !=
-                     self.directionCategory):
+                if (
+                    objekt.leftBond.directionCategory and
+                    objekt.leftBond.directionCategory != self.directionCategory
+                ):
                     incompatibles += [correspondence]
         return incompatibles
 
@@ -160,9 +165,11 @@ class Bond(WorkspaceStructure):
                     if object1.beside(object2):
                         slotSum += 1.0
                         for bond in self.string.bonds:
-                            if  (bond != self and
-                                 self.sameCategories(bond) and
-                                 self.myEnds(object1, object2)):
+                            if (
+                                bond != self and
+                                self.sameCategories(bond) and
+                                self.myEnds(object1, object2)
+                            ):
                                 supportSum += 1.0
         try:
             return 100.0 * supportSum / slotSum
@@ -185,20 +192,23 @@ def possibleGroupBonds(bondCategory, directionCategory, bondFacet, bonds):
     result = []
     for bond in bonds:
         slipnet = bond.ctx.slipnet
-        if  (bond.category == bondCategory and
-             bond.directionCategory == directionCategory):
+        if (
+            bond.category == bondCategory and
+            bond.directionCategory == directionCategory
+        ):
             result += [bond]
         else:
             # a modified bond might be made
-            if bondCategory == slipnet.sameness:
+            if bond.category == bondCategory:
                 return None  # a different bond cannot be made here
-            if  (bond.category == bondCategory or
-                 bond.directionCategory == directionCategory):
+            if bond.directionCategory == directionCategory:
                 return None  # a different bond cannot be made here
-            if bond.category == slipnet.sameness:
+            if slipnet.sameness in [bondCategory, bond.category]:
                 return None
-            bond = Bond(bond.ctx, bond.destination, bond.source, bondCategory,
-                        bondFacet, bond.destinationDescriptor,
-                        bond.sourceDescriptor)
+            bond = Bond(
+                bond.ctx, bond.destination, bond.source, bondCategory,
+                bondFacet, bond.destinationDescriptor,
+                bond.sourceDescriptor
+            )
             result += [bond]
     return result
diff --git a/copycat/codeletMethods.py b/copycat/codeletMethods.py
index aad3f8e..985a81c 100644
--- a/copycat/codeletMethods.py
+++ b/copycat/codeletMethods.py
@@ -356,17 +356,18 @@ def replacement_finder(ctx, codelet):
     position = letterOfInitialString.leftIndex
     moreLetters = [o for o in workspace.modified.objects
                    if isinstance(o, Letter) and o.leftIndex == position]
-    letterOfModifiedString = moreLetters and moreLetters[0] or None
-    assert letterOfModifiedString
-    position -= 1
-    initialAscii = ord(workspace.initialString[position])
-    modifiedAscii = ord(workspace.modifiedString[position])
+    if not moreLetters:
+        return
+    letterOfModifiedString = moreLetters[0]
+    initialAscii = ord(workspace.initialString[position - 1])
+    modifiedAscii = ord(workspace.modifiedString[position - 1])
     diff = initialAscii - modifiedAscii
     if abs(diff) < 2:
         relations = {
             0: slipnet.sameness,
             -1: slipnet.successor,
-            1: slipnet.predecessor}
+            1: slipnet.predecessor
+        }
         relation = relations[diff]
         logging.info('Relation found: %s', relation.name)
     else:
diff --git a/copycat/conceptMapping.py b/copycat/conceptMapping.py
index dc15d32..34201f0 100644
--- a/copycat/conceptMapping.py
+++ b/copycat/conceptMapping.py
@@ -22,7 +22,7 @@ class ConceptMapping(object):
             self.__str__(), self.initialDescriptor, self.targetDescriptor)
 
     def __str__(self):
-        return self.label and self.label.name or 'anonymous'
+        return self.label.name if self.label else 'anonymous'
 
     def slippability(self):
         association = self.__degreeOfAssociation()
@@ -125,9 +125,8 @@ class ConceptMapping(object):
         # means that letter->group supports letter->group, even though these
         # concept-mappings have no label.
 
-        if self.initialDescriptor == other.initialDescriptor:
-            if self.targetDescriptor == other.targetDescriptor:
-                return True
+        if self.sameDescriptors(other):
+            return True
         # if the descriptors are not related return false
         if not self.related(other):
             return False
diff --git a/copycat/copycat.py b/copycat/copycat.py
index bfeec9a..ee0e6dd 100644
--- a/copycat/copycat.py
+++ b/copycat/copycat.py
@@ -1,5 +1,3 @@
-import logging
-
 from coderack import Coderack
 from randomness import Randomness
 from slipnet import Slipnet
diff --git a/copycat/curses_main.py b/copycat/curses_main.py
index a4e8d46..19bb441 100644
--- a/copycat/curses_main.py
+++ b/copycat/curses_main.py
@@ -1,7 +1,6 @@
 import argparse
 import curses
 import logging
-import sys
 
 from copycat import Copycat
 from curses_reporter import CursesReporter
diff --git a/copycat/main.py b/copycat/main.py
index 94fbc5c..27ab66c 100644
--- a/copycat/main.py
+++ b/copycat/main.py
@@ -1,6 +1,5 @@
 import argparse
 import logging
-import sys
 
 from copycat import Copycat, Reporter
 
diff --git a/copycat/slipnet.py b/copycat/slipnet.py
index 4a4713a..3478abf 100644
--- a/copycat/slipnet.py
+++ b/copycat/slipnet.py
@@ -7,23 +7,10 @@ from sliplink import Sliplink
 class Slipnet(object):
     # pylint: disable=too-many-instance-attributes
     def __init__(self):
-        logging.debug("Slipnet.__init__()")
-        self.slipnodes = []
-        self.sliplinks = []
-        self.bondFacets = []
-        self.numberOfUpdates = 0
         self.__addInitialNodes()
         self.__addInitialLinks()
         self.reset()
 
-    def __repr__(self):
-        return '<slipnet>'
-
-    def setConceptualDepths(self, depth):
-        logging.debug('slipnet set all depths to %f', depth)
-        for node in self.slipnodes:
-            node.setConceptualDepth(depth)
-
     def reset(self):
         logging.debug('slipnet.reset()')
         self.numberOfUpdates = 0
@@ -126,8 +113,10 @@ class Slipnet(object):
         self.bondFacet = self.__addNode('bondFacet', 90.0)
 
         # specify the descriptor types that bonds can form between
-        self.bondFacets += [self.letterCategory]
-        self.bondFacets += [self.length]
+        self.bondFacets = [
+            self.letterCategory,
+            self.length,
+        ]
 
         # some factors are considered "very relevant" a priori
         self.initiallyClampedSlipnodes = [
diff --git a/copycat/workspace.py b/copycat/workspace.py
index df357a9..913ea56 100644
--- a/copycat/workspace.py
+++ b/copycat/workspace.py
@@ -23,7 +23,8 @@ class Workspace(object):
 
     def __repr__(self):
         return '<Workspace trying %s:%s::%s:?>' % (
-            self.initialString, self.modifiedString, self.targetString)
+            self.initialString, self.modifiedString, self.targetString,
+        )
 
     def resetWithStrings(self, initial, modified, target):
         self.targetString = target
@@ -136,11 +137,10 @@ class Workspace(object):
     def slippages(self):
         result = []
         if self.changedObject and self.changedObject.correspondence:
-            result = [m for m in
-                      self.changedObject.correspondence.conceptMappings]
-        for objekt in self.initial.objects:
-            if objekt.correspondence:
-                for mapping in objekt.correspondence.slippages():
+            result = self.changedObject.correspondence.conceptMappings[:]
+        for o in self.initial.objects:
+            if o.correspondence:
+                for mapping in o.correspondence.slippages():
                     if not mapping.isNearlyContainedBy(result):
                         result += [mapping]
         return result
diff --git a/copycat/workspaceFormulas.py b/copycat/workspaceFormulas.py
index 6a7ea8e..9c76474 100644
--- a/copycat/workspaceFormulas.py
+++ b/copycat/workspaceFormulas.py
@@ -1,5 +1,6 @@
 import logging
 
+
 def __chooseObjectFromList(ctx, objects, attribute):
     random = ctx.random
     temperature = ctx.temperature