code sample for pandas-dev#41951

Author: simonjayhawkins

bisect/41951.py

@@ -0,0 +1,17 @@
+# DataFrame.melt fails if there are duplicate value_vars #41951
+
+import pandas as pd
+
+print(pd.__version__)
+
+df = pd.DataFrame([["id", 2, 3]]).set_axis(["id_var", "value_var", "value_var"], axis=1)
+
+result = df.melt(id_vars=["id_var"], value_vars=["value_var"])
+print(result)
+
+expected = pd.DataFrame(
+    {"id_var": ["id", "id"], "variable": ["value_var", "value_var"], "value": [2, 3]}
+)
+expected
+
+pd.testing.assert_frame_equal(result, expected)