fix astanin#180 - exception on empty data with maxcolwidths option

Author: astanin

tabulate/__init__.py

@@ -1503,7 +1503,11 @@ def _normalize_tabular_data(tabular_data, headers, showindex="default"):
 
 
 def _wrap_text_to_colwidths(list_of_lists, colwidths, numparses=True):
-    numparses = _expand_iterable(numparses, len(list_of_lists[0]), True)
+    if len(list_of_lists):
+        num_cols = len(list_of_lists[0])
+    else:
+        num_cols = 0
+    numparses = _expand_iterable(numparses, num_cols, True)
 
     result = []
 
@@ -2062,7 +2066,10 @@ def tabulate(
     list_of_lists, separating_lines = _remove_separating_lines(list_of_lists)
 
     if maxcolwidths is not None:
-        num_cols = len(list_of_lists[0])
+        if len(list_of_lists):
+            num_cols = len(list_of_lists[0])
+        else:
+            num_cols = 0
         if isinstance(maxcolwidths, int):  # Expand scalar for all columns
             maxcolwidths = _expand_iterable(maxcolwidths, num_cols, maxcolwidths)
         else:  # Ignore col width for any 'trailing' columns

test/test_regression.py

@@ -486,3 +486,9 @@ def test_preserve_line_breaks_with_maxcolwidths():
     )
     result = tabulate(table, tablefmt="grid", maxcolwidths=10)
     assert_equal(result, expected)
+
+
+def test_exception_on_empty_data_with_maxcolwidths():
+    "Regression: exception on empty data when using maxcolwidths (github issue #180)"
+    result = tabulate([], maxcolwidths=5)
+    assert_equal(result, "")