diff --git a/python/damask/_asciitable.py b/python/damask/_asciitable.py
index 8410b23a1..9d762369a 100644
--- a/python/damask/_asciitable.py
+++ b/python/damask/_asciitable.py
@@ -157,7 +157,7 @@ class ASCIItable():
   def head_write(self,
                  header = True):
     """Write current header information (info + labels)."""
-    head = ['{}\theader'.format(len(self.info)+self.__IO__['labeled'])] if header else []
+    head = [f"{len(self.info)+self.__IO__['labeled']}\theader"] if header else []
     head.append(self.info)
     if self.__IO__['labeled']:
       head.append('\t'.join(map(self._quote,self.tags)))
@@ -209,7 +209,7 @@ class ASCIItable():
           labelList.append(tags[id])
         else:
           label = tags[id][2:]                                                                    # get label
-          while id < len(tags) and tags[id] == '{}_{}'.format(dim,label):                         # check successors
+          while id < len(tags) and tags[id] == f'{dim}_{label}':                                  # check successors
             id  += 1                                                                              # next label...
             dim += 1                                                                              # ...should be one higher dimension
           labelList.append(label)                                                                 # reached end --> store
diff --git a/python/damask/grid_filters.py b/python/damask/grid_filters.py
index 76ab20872..6c3f24cff 100644
--- a/python/damask/grid_filters.py
+++ b/python/damask/grid_filters.py
@@ -233,7 +233,7 @@ def cell_coord0_gridSizeOrigin(coord0,ordered=True):
     origin[_np.where(grid==1)] = 0.0
 
     if grid.prod() != len(coord0):
-        raise ValueError('Data count {} does not match grid {}.'.format(len(coord0),grid))
+        raise ValueError('Data count {len(coord0)} does not match grid {grid}.')
 
     start = origin + delta*.5
     end   = origin - delta*.5 + size
@@ -384,7 +384,7 @@ def node_coord0_gridSizeOrigin(coord0,ordered=True):
     origin    = mincorner
 
     if (grid+1).prod() != len(coord0):
-        raise ValueError('Data count {} does not match grid {}.'.format(len(coord0),grid))
+        raise ValueError('Data count {len(coord0)} does not match grid {grid}.')
 
     atol = _np.max(size)*5e-2
     if not (_np.allclose(coords[0],_np.linspace(mincorner[0],maxcorner[0],grid[0]+1),atol=atol) and \
diff --git a/python/damask/util.py b/python/damask/util.py
index a3fc71d3a..f67df461a 100644
--- a/python/damask/util.py
+++ b/python/damask/util.py
@@ -125,7 +125,7 @@ def execute(cmd,
     stdout = stdout.decode('utf-8').replace('\x08','')
     stderr = stderr.decode('utf-8').replace('\x08','')
     if process.returncode != 0:
-        raise RuntimeError('{} failed with returncode {}'.format(cmd,process.returncode))
+        raise RuntimeError(f'{cmd} failed with returncode {process.returncode}')
     return stdout, stderr
 
 
@@ -223,21 +223,20 @@ class _ProgressBar:
         self.start_time = datetime.datetime.now()
         self.last_fraction = 0.0
 
-        sys.stderr.write('{} {}   0% ETA n/a'.format(self.prefix, '░'*self.bar_length))
+        sys.stderr.write(f"{self.prefix} {'░'*self.bar_length}   0% ETA n/a")
         sys.stderr.flush()
 
     def update(self,iteration):
 
         fraction = (iteration+1) / self.total
+        filled_length = int(self.bar_length * fraction)
 
-        if int(self.bar_length * fraction) > int(self.bar_length *  self.last_fraction):
+        if filled_length > int(self.bar_length * self.last_fraction):
+            bar = '█' * filled_length + '░' * (self.bar_length - filled_length)
             delta_time = datetime.datetime.now() - self.start_time
             remaining_time = (self.total - (iteration+1)) * delta_time / (iteration+1)
             remaining_time -= datetime.timedelta(microseconds=remaining_time.microseconds)           # remove μs
-
-            filled_length = int(self.bar_length * fraction)
-            bar = '█' * filled_length + '░' * (self.bar_length - filled_length)
-            sys.stderr.write('\r{} {} {:>4.0%} ETA {}'.format(self.prefix, bar, fraction, remaining_time))
+            sys.stderr.write('\r{self.prefix} {bar} {fraction:>4.0%} ETA {remaining_time}')
             sys.stderr.flush()
 
         self.last_fraction = fraction
@@ -249,7 +248,7 @@ class _ProgressBar:
 
 class bcolors:
     """
-    ASCII Colors.
+    ASCII colors.
 
     https://svn.blender.org/svnroot/bf-blender/trunk/blender/build_files/scons/tools/bcolors.py
     https://stackoverflow.com/questions/287871