code sample for pandas-dev#42437

Author: simonjayhawkins

bisect/42437.py

@@ -0,0 +1,54 @@
+# BUG: Assigning extension array value to series of dtype object fails if element type is array-like #42437
+
+import pandas as pd
+from pandas.api.extensions import (
+    ExtensionArray,
+    ExtensionDtype,
+)
+
+print(pd.__version__)
+
+
+class StubDtype(ExtensionDtype):
+    """Extension dtype whose elements are something that numpy.asarray()
+    will turn into an array (in this case a tuple)"""
+
+    def __init__(self):
+        pass
+
+    @property
+    def type(self):
+        return tuple
+
+    @property
+    def name(self) -> str:
+        return "StubDtype"
+
+    @classmethod
+    def construct_array_type(cls):
+        return StubExtensionArray()
+
+
+class StubExtensionArray(ExtensionArray):
+    """Just enough of an extension array to run the four lines of code
+    that follow."""
+
+    @property
+    def dtype(self):
+        return StubDtype()
+
+    def copy(self):
+        return StubExtensionArray()
+
+    def __len__(self):
+        return 5
+
+    def __getitem__(self, key):
+        # Every position in the array has the tuple (1, 2, 3)
+        return (1, 2, 3)
+
+
+data = StubExtensionArray()
+series1 = pd.Series(data, name="data")
+series2 = pd.Series(index=series1.index, dtype=object, name="data")
+series2.loc[series1.index] = data