code sample for pandas-dev#47867

Author: simonjayhawkins

bisect/47867.py

@@ -0,0 +1,35 @@
+# BUG: Update Values from MultiIndex Dataframe after using loc is not applied correctly #47867
+
+import numpy as np
+import pandas as pd
+
+print(pd.__version__)
+
+df = pd.DataFrame()
+df["idx1"] = [0, 1, 2, 3, 4]
+df["idx2"] = [0, 1, 2, 3, 4]
+df["abool"] = True
+df["a"] = np.arange(5, dtype="int64")
+df["b"] = np.arange(5, dtype="float64")
+df["c"] = np.arange(5, dtype="int64")
+df = df.set_index(["idx1", "idx2"])
+
+idx = [(1, 1), (3, 3)]
+df.loc[idx, "c"] = 0
+df.loc[idx, "c"]
+
+df.loc[idx, ["a", "b"]]  # This line is the problem
+
+df.loc[idx, "c"] = 15
+result = df.loc[idx, "c"]
+print(result)
+# idx1  idx2
+# 1     1       15
+# 3     3       15
+# Name: c, dtype: int64
+
+expected = pd.Series(
+    [15, 15], index=pd.MultiIndex.from_tuples(idx, names=["idx1", "idx2"]), name="c"
+)
+
+pd.testing.assert_series_equal(result, expected)

bisect/47871.py

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+# BUG: to_csv requires escapechar unnecessarily when data contains
+# null byte \x00 (PowerShell only) #47871
+
+import pandas as pd
+
+print(pd.__version__)
+
+df = pd.DataFrame({"A": ["\x00"]})
+df.to_csv("null_byte.csv", index=False)