Prevent duplicate bars when redrawing vertical charts

termgraph/chart.py

@@ -359,6 +359,10 @@ def _prepare_vertical(self, value: float, num_blocks: int):
 
     def draw(self) -> None:
         """Draws the vertical chart"""
+        self.value_list.clear()
+        self.zipped_list.clear()
+        self.vertical_list.clear()
+        self.maxi = 0
         self._print_header()
 
         colors = self.args.get_arg("colors")

tests/test_chart_redraw.py

@@ -0,0 +1,20 @@
+import pytest
+
+from termgraph.args import Args
+from termgraph.chart import BarChart, StackedChart, VerticalChart
+from termgraph.data import Data
+
+
+@pytest.mark.parametrize("chart_type", [BarChart, StackedChart, VerticalChart])
+@pytest.mark.parametrize("options", [{}, {"no_values": True}, {"no_labels": True}])
+def test_drawing_chart_again_preserves_output(capsys, chart_type, options):
+    data = Data([[3], [5]], ["A", "B"])
+    chart = chart_type(data, Args(width=5, **options))
+
+    chart.draw()
+    expected = capsys.readouterr().out
+    assert "▇" in expected
+
+    for _ in range(2):
+        chart.draw()
+        assert capsys.readouterr().out == expected