Merge branch '149-python-vtk-improvements' into 'development'

don't add empty strings

Closes #149

See merge request damask/DAMASK!673

python/damask/_vtk.py

@@ -116,7 +116,10 @@ class VTK:
         """
         s = vtk.vtkStringArray()
         s.SetName('comments')
-        for c in util.tail_repack(comments,self.comments):
+        comments_ = util.tail_repack(comments,self.comments) if comments[:len(self.comments)] == self.comments else \
+                    [comments] if isinstance(comments,str) else \
+                    comments
+        for c in comments_:
             s.InsertNextValue(c)
         self.vtk_data.GetFieldData().AddArray(s)
 
@@ -547,9 +550,11 @@ class VTK:
 
         Notes
         -----
-            See http://compilatrix.com/article/vtk-1 for further ideas.
+        The first component is shown when visualizing vector datasets
+        (this includes tensor datasets because they are flattened).
 
         """
+        # See http://compilatrix.com/article/vtk-1 for possible improvements.
         try:
             import wx
             _ = wx.App(False)                                                                       # noqa

python/damask/util.py

@@ -793,7 +793,7 @@ def tail_repack(extended: _Union[str, _Sequence[str]],
 
     Parameters
     ----------
-    extended : (list of) str
+    extended : (sequence of) str
         Extended string list with potentially autosplitted tailing string relative to `existing`.
     existing : list of str
         Base string list.
@@ -811,9 +811,9 @@ def tail_repack(extended: _Union[str, _Sequence[str]],
         ['a','new','shiny','e','n','t','r','y']
 
     """
-    return [extended] if isinstance(extended,str) else existing + \
-         ([''.join(extended[len(existing):])] if _np.prod([len(i) for i in extended[len(existing):]]) == 1 else
-          list(extended[len(existing):]))
+    new = extended[len(existing):]
+    return [extended] if isinstance(extended,str) else \
+           existing + list([''.join(new)] if _np.prod([len(i) for i in new]) == 1 else new)
 
 
 def aslist(arg: _Union[_IntCollection, int, None]) -> _List: