code sample for pandas-dev#39595

Author: simonjayhawkins

bisect/39595.py

@@ -0,0 +1,14 @@
+import pandas as pd
+
+print(pd.__version__)
+
+df1 = pd.DataFrame([1, 2, 3, 4], columns=["w"])
+df2 = pd.DataFrame([1, 2, 3, 4], columns=["w"])
+c1 = df1["w"].where(df1["w"] < 4, 4)
+c2 = df2["w"].where(df2["w"] < 5)
+c1 *= 2
+c2 *= 2
+print(df1["w"])
+print(df2["w"])
+assert (c1 == c2).all()
+assert (df1["w"] == df2["w"]).all()  # df2 got changed, so assertion fails