diff --git a/io_anim_c3d/import_c3d.py b/io_anim_c3d/import_c3d.py
index febdef35b04bb93c941ca7430bda738090b89c12..0c8cd8f2bfb95c6b3665ec10ea961673120cbf55 100644
--- a/io_anim_c3d/import_c3d.py
+++ b/io_anim_c3d/import_c3d.py
@@ -183,7 +183,7 @@ class MarkerSet:
         (ig, ig, pointIdx,
          self.procType) = struct.unpack('BBBB', infile.read(4))
         self.procType -= 83
-        if self.procType not in (1, 2):
+        if self.procType not in {1, 2}:
             # 1(INTEL-PC); 2(DEC-VAX); 3(MIPS-SUN/SGI)
             print('Warning: importer was not tested for files from '
                   'architectures other than Intel-PC and DEC-VAX')
diff --git a/io_export_dxf/primitive_exporters/mesh_exporter.py b/io_export_dxf/primitive_exporters/mesh_exporter.py
index 56509e32cb83db2473d821ed37a8e46fc77e07b6..9764796b3383243f3945a1b83565ce5e41f55f9a 100644
--- a/io_export_dxf/primitive_exporters/mesh_exporter.py
+++ b/io_export_dxf/primitive_exporters/mesh_exporter.py
@@ -112,7 +112,7 @@ class MeshDXFExporter(BasePrimitiveDXFExporter):
                     args = copy.copy(kwargs)
                     args['points'] = points
                     entities.append(('Line', args))
-        elif c in ('POLYFACE','POLYLINE'):
+        elif c in {'POLYFACE', 'POLYLINE'}:
             if faces and allpoints:
                 #TODO: purge allpoints: left only vertices used by faces
 #                    if exportsettings['verbose']: 
diff --git a/io_export_dxf/primitive_exporters/text_exporter.py b/io_export_dxf/primitive_exporters/text_exporter.py
index c7e9d17339f7f425e064def5f3e4a3b460cd608e..98693aec0c76ac039721371762f8e6fac17e93f7 100644
--- a/io_export_dxf/primitive_exporters/text_exporter.py
+++ b/io_export_dxf/primitive_exporters/text_exporter.py
@@ -36,7 +36,7 @@ def exportText(ob, mx, mw, **common):
     #3=aligned, 4=middle, 5=fit
     Alignment = None
     alignment = text3d.getAlignment().value
-    if alignment in (1,2): Alignment = alignment
+    if alignment in {1, 2}: Alignment = alignment
 
     textHeight = text3d.getSize() / 1.7
     textFlag = 0
diff --git a/io_import_gimp_image_to_scene.py b/io_import_gimp_image_to_scene.py
index a39ef1edc79cea56bfb60cd38b2e9ad039646971..4605fe1d96c83a1b687c557fd91fb4fe950cb7cc 100644
--- a/io_import_gimp_image_to_scene.py
+++ b/io_import_gimp_image_to_scene.py
@@ -471,29 +471,29 @@ def main(File, Path, LayerViewers, MixerViewers, LayerOffset,
                 Mode = LayerList[Offset][1] # has to go one step further
                 LayerOpacity = LayerList[Offset][2]
                 
-                if not Mode in ('Normal', '-1'):
+                if not Mode in {'Normal', '-1'}:
                     
                     Node = Tree.nodes.new('MIX_RGB')
                     if OpacityMode == 'COMPO': Node.inputs['Fac'].default_value[0] = LayerOpacity
                     else: Node.inputs['Fac'].default_value[0] = 1
                     Node.use_alpha = True
                     
-                    if Mode in ('Addition', '7'): Node.blend_type = 'ADD'
-                    elif Mode in ('Subtract', '8'): Node.blend_type = 'SUBTRACT'
-                    elif Mode in ('Multiply', '3'): Node.blend_type = 'MULTIPLY'
-                    elif Mode in ('DarkenOnly', '9'): Node.blend_type = 'DARKEN'
-                    elif Mode in ('Dodge', '16'): Node.blend_type = 'DODGE'
-                    elif Mode in ('LightenOnly', '10'): Node.blend_type = 'LIGHTEN'
-                    elif Mode in ('Difference', '6'): Node.blend_type = 'DIFFERENCE'
-                    elif Mode in ('Divide', '15'): Node.blend_type = 'DIVIDE'
-                    elif Mode in ('Overlay', '5'): Node.blend_type = 'OVERLAY'
-                    elif Mode in ('Screen', '4'): Node.blend_type = 'SCREEN'
-                    elif Mode in ('Burn', '17'): Node.blend_type = 'BURN'
-                    elif Mode in ('Color', '13'): Node.blend_type = 'COLOR'
-                    elif Mode in ('Value', '14'): Node.blend_type = 'VALUE'
-                    elif Mode in ('Saturation', '12'): Node.blend_type = 'SATURATION'
-                    elif Mode in ('Hue', '11'): Node.blend_type = 'HUE'
-                    elif Mode in ('Softlight', '19'): Node.blend_type = 'SOFT_LIGHT'
+                    if Mode in {'Addition', '7'}: Node.blend_type = 'ADD'
+                    elif Mode in {'Subtract', '8'}: Node.blend_type = 'SUBTRACT'
+                    elif Mode in {'Multiply', '3'}: Node.blend_type = 'MULTIPLY'
+                    elif Mode in {'DarkenOnly', '9'}: Node.blend_type = 'DARKEN'
+                    elif Mode in {'Dodge', '16'}: Node.blend_type = 'DODGE'
+                    elif Mode in {'LightenOnly', '10'}: Node.blend_type = 'LIGHTEN'
+                    elif Mode in {'Difference', '6'}: Node.blend_type = 'DIFFERENCE'
+                    elif Mode in {'Divide', '15'}: Node.blend_type = 'DIVIDE'
+                    elif Mode in {'Overlay', '5'}: Node.blend_type = 'OVERLAY'
+                    elif Mode in {'Screen', '4'}: Node.blend_type = 'SCREEN'
+                    elif Mode in {'Burn', '17'}: Node.blend_type = 'BURN'
+                    elif Mode in {'Color', '13'}: Node.blend_type = 'COLOR'
+                    elif Mode in {'Value', '14'}: Node.blend_type = 'VALUE'
+                    elif Mode in {'Saturation', '12'}: Node.blend_type = 'SATURATION'
+                    elif Mode in {'Hue', '11'}: Node.blend_type = 'HUE'
+                    elif Mode in {'Softlight', '19'}: Node.blend_type = 'SOFT_LIGHT'
                     else: pass
                     
                 else:
@@ -517,7 +517,7 @@ def main(File, Path, LayerViewers, MixerViewers, LayerOffset,
         Nodes = bpy.context.scene.node_tree.nodes
         
         if LayerLen > 1:
-            for i in range (1, LayerLen+1):
+            for i in range (1, LayerLen + 1):
                 if i == 1:
                     Tree.links.new(Nodes['R_'+str(i)].outputs[0], Nodes['M_'+str(i)].inputs[1])
                 if 1 < i < LayerLen:
diff --git a/netrender/client.py b/netrender/client.py
index 3cb0b4372f23d91b1b9dcde0f01f202ac942d6db..0ad9a1e43f70edcde96e2b09577d14714d0fcdf1 100644
--- a/netrender/client.py
+++ b/netrender/client.py
@@ -140,7 +140,7 @@ def sendJobVCS(conn, scene, anim = False):
 
     filename = filename[len(netsettings.vcs_wpath):]
     
-    if filename[0] in (os.sep, os.altsep):
+    if filename[0] in {os.sep, os.altsep}:
         filename = filename[1:]
     
     job.addFile(filename, signed=False)
diff --git a/netrender/master.py b/netrender/master.py
index 593ee727aa56927392137a303fc10392d6b8abff..3c087e5818f2ed288898eb5061fb2d3bbc69b7d7 100644
--- a/netrender/master.py
+++ b/netrender/master.py
@@ -311,7 +311,7 @@ class RenderHandler(http.server.BaseHTTPRequestHandler):
                     frame = job[frame_number]
 
                     if frame:
-                        if frame.status in (netrender.model.FRAME_QUEUED, netrender.model.FRAME_DISPATCHED):
+                        if frame.status in {netrender.model.FRAME_QUEUED, netrender.model.FRAME_DISPATCHED}:
                             self.send_head(http.client.ACCEPTED)
                         elif frame.status == netrender.model.FRAME_DONE:
                             self.server.stats("", "Sending result to client")
@@ -379,7 +379,7 @@ class RenderHandler(http.server.BaseHTTPRequestHandler):
                     frame = job[frame_number]
 
                     if frame:
-                        if frame.status in (netrender.model.FRAME_QUEUED, netrender.model.FRAME_DISPATCHED):
+                        if frame.status in {netrender.model.FRAME_QUEUED, netrender.model.FRAME_DISPATCHED}:
                             self.send_head(http.client.ACCEPTED)
                         elif frame.status == netrender.model.FRAME_DONE:
                             filename = job.getResultPath(frame.getRenderFilename())
@@ -419,7 +419,7 @@ class RenderHandler(http.server.BaseHTTPRequestHandler):
                     frame = job[frame_number]
 
                     if frame:
-                        if not frame.log_path or frame.status in (netrender.model.FRAME_QUEUED, netrender.model.FRAME_DISPATCHED):
+                        if not frame.log_path or frame.status in {netrender.model.FRAME_QUEUED, netrender.model.FRAME_DISPATCHED}:
                             self.send_head(http.client.PROCESSING)
                         else:
                             self.server.stats("", "Sending log to client")
diff --git a/netrender/ui.py b/netrender/ui.py
index 4aa085c94d4c84a1b750d15546d539ed6bff4395..319c1067fcc8c2a1f1d2d17c21e2d7159667d1e4 100644
--- a/netrender/ui.py
+++ b/netrender/ui.py
@@ -116,7 +116,7 @@ class RENDER_PT_network_settings(NetRenderButtonsPanel, bpy.types.Panel):
 
         layout.prop(netsettings, "mode", expand=True)
 
-        if netsettings.mode in ("RENDER_MASTER", "RENDER_SLAVE"):
+        if netsettings.mode in {'RENDER_MASTER', 'RENDER_SLAVE'}:
             layout.operator("render.netclientstart", icon='PLAY')
 
         layout.prop(netsettings, "path")
diff --git a/space_view3d_copy_attributes.py b/space_view3d_copy_attributes.py
index 4f090716d3611a7840046dda1eca18f1da4667cf..ddfcd4430dfc7f307fc04471fa2924dea9416492 100644
--- a/space_view3d_copy_attributes.py
+++ b/space_view3d_copy_attributes.py
@@ -691,7 +691,7 @@ class MESH_OT_CopyFaceSettings(bpy.types.Operator):
 
     def execute(self, context):
         mode = getattr(self, 'mode', '')
-        if not mode in ('MAT', 'VCOL', 'IMAGE', 'UV'):
+        if not mode in {'MAT', 'VCOL', 'IMAGE', 'UV'}:
             self.report({'ERROR'}, "No mode specified or invalid mode.")
             return self._end(context, {'CANCELLED'})
         layername = getattr(self, 'layer', '')