Index: src/sas/sasgui/perspectives/calculator/gen_scatter_panel.py
===================================================================
--- src/sas/sasgui/perspectives/calculator/gen_scatter_panel.py	(revision 235f514ba93b57fa63e44309f182acef0b98bb55)
+++ src/sas/sasgui/perspectives/calculator/gen_scatter_panel.py	(revision ac07a3acc20dbf79c564bf642aece71a02c2c862)
@@ -1914,5 +1914,5 @@
             return
         self.sld_data = data
-        enable = (not data is None)
+        enable = (data is not None)
         self._set_omfpanel_sld_data(self.sld_data)
         self.omfpanel.bt_save.Enable(enable)
Index: src/sas/sasgui/perspectives/pr/pr.py
===================================================================
--- src/sas/sasgui/perspectives/pr/pr.py	(revision 235f514ba93b57fa63e44309f182acef0b98bb55)
+++ src/sas/sasgui/perspectives/pr/pr.py	(revision ac07a3acc20dbf79c564bf642aece71a02c2c862)
@@ -291,5 +291,5 @@
         """
         qtemp = pr.x
-        if not q is None:
+        if q is not None:
             qtemp = q
 
@@ -303,7 +303,7 @@
 
         # Check for user min/max
-        if not pr.q_min is None:
+        if pr.q_min is not None:
             minq = pr.q_min
-        if not pr.q_max is None:
+        if pr.q_max is not None:
             maxq = pr.q_max
 
@@ -487,5 +487,5 @@
         scale = None
         min_err = 0.0
-        if not path is None:
+        if path is not None:
             input_f = open(path, 'r')
             buff = input_f.read()
@@ -512,5 +512,5 @@
                     logger.error(sys.exc_value)
 
-        if not scale is None:
+        if scale is not None:
             message = "The loaded file had no error bars, statistical errors are assumed."
             wx.PostEvent(self.parent, StatusEvent(status=message))
@@ -537,5 +537,5 @@
 
         data_started = False
-        if not path is None:
+        if path is not None:
             input_f = open(path, 'r')
             buff = input_f.read()
@@ -565,5 +565,5 @@
                     data_started = True
 
-        if not scale is None:
+        if scale is not None:
             message = "The loaded file had no error bars, statistical errors are assumed."
             wx.PostEvent(self.parent, StatusEvent(status=message))
@@ -761,5 +761,5 @@
         self.elapsed = elapsed
         self.control_panel.alpha_estimate = alpha
-        if not message is None:
+        if message is not None:
             wx.PostEvent(self.parent, StatusEvent(status=str(message)))
         self.perform_estimateNT()
@@ -779,5 +779,5 @@
         self.control_panel.nterms_estimate = nterms
         self.control_panel.alpha_estimate = alpha
-        if not message is None:
+        if message is not None:
             wx.PostEvent(self.parent, StatusEvent(status=str(message)))
 
@@ -921,5 +921,5 @@
         try:
             pr = self._create_plot_pr()
-            if not pr is None:
+            if pr is not None:
                 self.pr = pr
                 self.perform_inversion()
@@ -944,5 +944,5 @@
         try:
             pr = self._create_plot_pr()
-            if not pr is None:
+            if pr is not None:
                 self.pr = pr
                 self.perform_estimate()
@@ -1024,5 +1024,5 @@
         try:
             pr = self._create_file_pr(data)
-            if not pr is None:
+            if pr is not None:
                 self.pr = pr
                 self.perform_inversion()
Index: src/sas/sasgui/perspectives/pr/pr_thread.py
===================================================================
--- src/sas/sasgui/perspectives/pr/pr_thread.py	(revision 235f514ba93b57fa63e44309f182acef0b98bb55)
+++ src/sas/sasgui/perspectives/pr/pr_thread.py	(revision ac07a3acc20dbf79c564bf642aece71a02c2c862)
@@ -42,5 +42,5 @@
             pass
         except:
-            if not self.error_func is None:
+            if self.error_func is not None:
                 self.error_func("CalcPr.compute: %s" % sys.exc_value)
 
@@ -70,5 +70,5 @@
             pass
         except:
-            if not self.error_func is None:
+            if self.error_func is not None:
                 self.error_func("EstimatePr.compute: %s" % sys.exc_value)
 
@@ -110,4 +110,4 @@
             pass
         except:
-            if not self.error_func is None:
+            if self.error_func is not None:
                 self.error_func("EstimatePr2.compute: %s" % sys.exc_value)
