diff --git a/python/damask/_grid.py b/python/damask/_grid.py
index f7acfe5aa..4e82a4180 100644
--- a/python/damask/_grid.py
+++ b/python/damask/_grid.py
@@ -50,15 +50,16 @@ class Grid:
             Coordinates of grid origin in meter. Defaults to [0.0,0.0,0.0].
         initial_conditions : dictionary, optional
             Labels and values of the inital conditions at each material point.
-        comments : (list of) str, optional
-            Comments, e.g. history of operations.
+        comments : str or iterable of str, optional
+            Additional, human-readable information, e.g. history of operations.
 
         """
         self.material = material
         self.size = size                                                        # type: ignore
         self.origin = origin                                                    # type: ignore
         self.initial_conditions = {} if initial_conditions is None else initial_conditions
-        self.comments = [] if comments is None else comments                    # type: ignore
+        comments_ = [comments] if isinstance(comments,str) else comments
+        self.comments = [] if comments_ is None else [str(c) for c in comments_]
 
     def __repr__(self) -> str:
         """Give short human-readable summary."""
diff --git a/python/damask/_table.py b/python/damask/_table.py
index 03e62b2b4..1219cbc78 100644
--- a/python/damask/_table.py
+++ b/python/damask/_table.py
@@ -1,6 +1,6 @@
 import re
 import copy
-from typing import Union, Tuple, List
+from typing import Union, Tuple, List, Iterable
 
 import pandas as pd
 import numpy as np
@@ -14,7 +14,7 @@ class Table:
     def __init__(self,
                  shapes: dict,
                  data: np.ndarray,
-                 comments: Union[str, list] = None):
+                 comments: Union[str, Iterable[str]] = None):
         """
         New spreadsheet.
 
@@ -30,7 +30,7 @@ class Table:
 
         """
         comments_ = [comments] if isinstance(comments,str) else comments
-        self.comments = [] if comments_ is None else [c for c in comments_]
+        self.comments = [] if comments_ is None else [str(c) for c in comments_]
         self.shapes = { k:(v,) if isinstance(v,(np.int64,np.int32,int)) else v for k,v in shapes.items() }
         self.data = pd.DataFrame(data=data)
         self._relabel('uniform')
@@ -434,8 +434,8 @@ class Table:
 
 
     def rename(self,
-               old: Union[str, List[str]],
-               new: Union[str, List[str]],
+               old: Union[str, Iterable[str]],
+               new: Union[str, Iterable[str]],
                info: str = None) -> 'Table':
         """
         Rename column data.
diff --git a/python/damask/_vtk.py b/python/damask/_vtk.py
index 6baa16214..c41470638 100644
--- a/python/damask/_vtk.py
+++ b/python/damask/_vtk.py
@@ -103,7 +103,7 @@ class VTK:
 
         Parameters
         ----------
-        comments : str or list of str
+        comments : str or sequence of str
             Comments.
 
         """
@@ -153,11 +153,11 @@ class VTK:
 
         Parameters
         ----------
-        cells : iterable of int, len (3)
+        cells : sequence of int, len (3)
             Number of cells along each dimension.
-        size : iterable of float, len (3)
+        size : sequence of float, len (3)
             Physical length along each dimension.
-        origin : iterable of float, len (3), optional
+        origin : sequence of float, len (3), optional
             Coordinates of grid origin.
 
         Returns
@@ -257,7 +257,7 @@ class VTK:
 
         Parameters
         ----------
-        grid : iterables of floats, len (3)
+        grid : sequence of sequences of floats, len (3)
             Grid coordinates along x, y, and z directions.
 
         Returns