diff --git a/src/py/autowig/asg.py b/src/py/autowig/asg.py
index 69708057..cad27605 100644
--- a/src/py/autowig/asg.py
+++ b/src/py/autowig/asg.py
@@ -1591,26 +1591,26 @@ def add_directory(self, dirname):
         initname = str(dirname)
         if not initname.endswith(os.sep):
             initname += os.sep
-        if not initname in self._nodes:
+        if initname not in self._nodes:
             idparent = initname
-            if not idparent in self._syntax_edges:
+            if idparent not in self._syntax_edges:
                 self._syntax_edges[idparent] = []
             while not dirname == os.sep:
                 idnode = idparent
                 if not idnode.endswith(os.sep):
                     idnode += os.sep
-                if not idnode in self._nodes:
+                if idnode not in self._nodes:
                     self._nodes[idnode] = dict(_proxy=DirectoryProxy)
                     dirname = dirname.parent
                     idparent = str(dirname)
                     if not idparent.endswith(os.sep):
                         idparent += os.sep
-                    if not idparent in self._syntax_edges:
+                    if idparent not in self._syntax_edges:
                         self._syntax_edges[idparent] = []
                     self._syntax_edges[idparent].append(idnode)
                 else:
                     break
-            if dirname == os.sep and not os.sep in self._nodes:
+            if dirname == os.sep and os.sep not in self._nodes:
                 self._nodes[os.sep] = dict(_proxy=DirectoryProxy)
         return self[initname]
 
@@ -1618,13 +1618,13 @@ def add_file(self, filename, **kwargs):
         filename = path(filename).abspath()
         initname = str(filename)
         proxy = kwargs.pop('proxy', FileProxy)
-        if not initname in self._nodes:
+        if initname not in self._nodes:
             idnode = str(filename)
             self._nodes[idnode] = dict(_proxy=proxy, **kwargs)
             idparent = str(filename.parent)
             if not idparent.endswith(os.sep):
                 idparent += os.sep
-            if not idparent in self._syntax_edges:
+            if idparent not in self._syntax_edges:
                 self._syntax_edges[idparent] = []
             self._syntax_edges[idparent].append(idnode)
             self.add_directory(idparent)
@@ -1729,7 +1729,7 @@ def dependencies(self, *nodes):
 
         while len(white) > 0:
             node = white.pop()
-            if not node._node in black:
+            if node._node not in black:
                 black.add(node._node)
                 parent = node.parent
                 if not isinstance(parent, NamespaceProxy) and visitor(parent):
diff --git a/src/py/autowig/boost_python_generator.py b/src/py/autowig/boost_python_generator.py
index fbcfb17a..34d98401 100644
--- a/src/py/autowig/boost_python_generator.py
+++ b/src/py/autowig/boost_python_generator.py
@@ -674,7 +674,7 @@ def _feedback(self, row):
                             if not parsed:
                                 parsed = parse.parse('    class_{hash}.def({python}, {cpp}, {documentation});', line)
                             if parsed:
-                                if not 'what' in parsed.named:
+                                if 'what' not in parsed.named:
                                     if parsed['cpp'].startswith('method_pointer_'):
                                         pointer = parsed['cpp']
                                         parsed = None
diff --git a/src/py/autowig/libclang_parser.py b/src/py/autowig/libclang_parser.py
index abf04ba8..0cee10dc 100644
--- a/src/py/autowig/libclang_parser.py
+++ b/src/py/autowig/libclang_parser.py
@@ -282,7 +282,7 @@ def read_enum(asg, cursor, scope):
         return children
     else:
         spelling = 'enum ' + spelling
-        if not spelling in asg:
+        if spelling not in asg:
             asg._syntax_edges[spelling] = []
             asg._nodes[spelling] = dict(_proxy = EnumerationProxy,
                                         _comment = "",
@@ -334,7 +334,7 @@ def read_typedef(asg, typedef, scope):
         spelling = spelling + "::" + typedef.spelling
     else:
         spelling = spelling + typedef.spelling
-    if not spelling in asg:
+    if spelling not in asg:
         try:
             with warnings.catch_warnings():
                 warnings.simplefilter("error")
@@ -536,7 +536,7 @@ def read_tag(asg, cursor, scope):
             spelling = 'union ' + spelling
         else:
             spelling = 'class ' + spelling
-        if not spelling in asg:
+        if spelling not in asg:
             if cursor.kind in [CursorKind.STRUCT_DECL, CursorKind.UNION_DECL]:
                 asg._nodes[spelling] = dict(_proxy=ClassProxy,
                         _is_abstract=True,
@@ -614,11 +614,11 @@ def read_namespace(asg, cursor, scope):
         read_access(asg, cursor.access_specifier, *children)
         return children
     else:
-        if not spelling in asg:
+        if spelling not in asg:
             asg._nodes[spelling] = dict(_proxy=NamespaceProxy,
                                         _is_inline=False) # TODO
             asg._syntax_edges[spelling] = []
-        if not spelling in asg._syntax_edges[scope]:
+        if spelling not in asg._syntax_edges[scope]:
             asg._syntax_edges[scope].append(spelling)
         for child in cursor.get_children():
             read_cursor(asg, child, spelling)
diff --git a/src/py/autowig/proxy_manager.py b/src/py/autowig/proxy_manager.py
index 65c61154..0fa4c6f3 100644
--- a/src/py/autowig/proxy_manager.py
+++ b/src/py/autowig/proxy_manager.py
@@ -74,7 +74,7 @@ def __setitem__(self, proxy, cls):
         if issubclass(cls, self._base):
             self._cache[proxy] = cls
         elif isinstance(cls, basestring):
-            if not cls in self:
+            if cls not in self:
                 raise ValueError('\'cls\' parameter must be an existing proxy')
             if proxy == cls:
                 raise ValueError('\'proxy\' and \'cls\' parameters cannot have the same value')