diff --git a/python/damask/_geom.py b/python/damask/_geom.py
index 396ee64d0..6bc92e300 100644
--- a/python/damask/_geom.py
+++ b/python/damask/_geom.py
@@ -34,7 +34,7 @@ class Geom:
         self.set_origin(origin)
         self.set_homogenization(homogenization)
         self.set_comments(comments)
-      
+
 
     def __repr__(self):
         """Basic information on geometry definition."""
@@ -69,7 +69,7 @@ class Geom:
         origin_old  = self.get_origin()
         unique_old  = len(np.unique(self.microstructure))
         max_old     = np.nanmax(self.microstructure)
-        
+
         if size is not None and rescale:
             raise ValueError('Either set size explicitly or rescale automatically')
 
@@ -107,7 +107,7 @@ class Geom:
         if max_old != np.nanmax(self.microstructure):
             message[-1] = util.delete(message[-1])
             message.append(util.emph('max microstructure:  {}'.format(np.nanmax(self.microstructure))))
-        
+
         return util.return_message(message)
 
 
@@ -123,7 +123,7 @@ class Geom:
         """
         self.comments = []
         self.add_comments(comments)
-      
+
 
     def add_comments(self,comments):
         """
@@ -259,7 +259,7 @@ class Geom:
         header.append('origin x {} y {} z {}'.format(*self.get_origin()))
         header.append('homogenization {}'.format(self.get_homogenization()))
         return header
-        
+
 
     @staticmethod
     def from_file(fname):
@@ -285,7 +285,7 @@ class Geom:
         if not keyword.startswith('head') or header_length < 3:
             raise TypeError('Header length information missing or invalid')
 
-        comments = [] 
+        comments = []
         for i,line in enumerate(content[:header_length]):
             items = line.lower().strip().split()
             key = items[0] if items else ''
@@ -314,14 +314,14 @@ class Geom:
             else:                            items = list(map(float,items))
             microstructure[i:i+len(items)] = items
             i += len(items)
-        
+
         if i != grid.prod():
             raise TypeError('Invalid file: expected {} entries, found {}'.format(grid.prod(),i))
-        
+
         microstructure = microstructure.reshape(grid,order='F')
         if not np.any(np.mod(microstructure.flatten(),1) != 0.0):                                   # no float present
             microstructure = microstructure.astype('int')
-        
+
         return Geom(microstructure.reshape(grid),size,origin,homogenization,comments)
 
 
@@ -339,7 +339,7 @@ class Geom:
         """
         header = self.get_header()
         grid   = self.get_grid()
-        
+
         if pack is None:
             plain = grid.prod()/np.unique(self.microstructure).size < 250
         else:
@@ -390,7 +390,7 @@ class Geom:
             elif compressType == 'of':
                 f.write('{} of {}\n'.format(reps,former))
 
-                 
+
     def to_vtk(self,fname=None):
         """
         Generates vtk file.
@@ -409,7 +409,7 @@ class Geom:
         else:
             sys.stdout.write(v.__repr__())
 
-                 
+
     def show(self):
         """Show raw content (as in file)."""
         f=StringIO()
@@ -445,7 +445,7 @@ class Geom:
             ms = np.concatenate([ms,ms[:,limits[0]:limits[1]:-1,:]],1)
         if 'x' in directions:
             ms = np.concatenate([ms,ms[limits[0]:limits[1]:-1,:,:]],0)
-     
+
         #self.add_comments('geom.py:mirror v{}'.format(version)
         return self.update(ms,rescale=True)
 
diff --git a/python/damask/_table.py b/python/damask/_table.py
index 72214a357..9cb09fb3b 100644
--- a/python/damask/_table.py
+++ b/python/damask/_table.py
@@ -46,7 +46,7 @@ class Table:
 
 
     def _add_comment(self,label,shape,info):
-        if info:
+        if info is not None:
             c = '{}{}: {}'.format(label,' '+str(shape) if np.prod(shape,dtype=int) > 1 else '',info)
             self.comments.append(c)
 
@@ -251,7 +251,7 @@ class Table:
 
         """
         self.data.rename(columns={label_old:label_new},inplace=True)
-        c = '{} => {}{}'.format(label_old,label_new,'' if not info else ': {}'.format(info))
+        c = '{} => {}{}'.format(label_old,label_new,'' if info is None else ': {}'.format(info))
         self.comments.append(c)
         self.shapes = {(label if label != label_old else label_new):self.shapes[label] for label in self.shapes}
 
diff --git a/python/damask/_vtk.py b/python/damask/_vtk.py
index 3de345eb6..92b4be064 100644
--- a/python/damask/_vtk.py
+++ b/python/damask/_vtk.py
@@ -131,7 +131,7 @@ class VTK:
             reader = vtk.vtkGenericDataObjectReader()
             reader.SetFileName(fname)
             reader.Update()
-            if not dataset_type:
+            if dataset_type is None:
                 raise TypeError('Dataset type for *.vtk file not given.')
             elif dataset_type.lower().endswith('rectilineargrid'):
                 geom = reader.GetRectilinearGridOutput()
@@ -196,7 +196,7 @@ class VTK:
 
         if   isinstance(data,np.ndarray):
             d = np_to_vtk(num_array=data.reshape(data.shape[0],-1),deep=True)
-            if not label:
+            if label is None:
                 raise ValueError('No label defined for numpy.ndarray')
             d.SetName(label)
             if   data.shape[0] == N_cells: