done

lib/python3.11/site-packages/pandas/tests/frame/methods/test_copy.py

@@ -0,0 +1,64 @@
+import numpy as np
+import pytest
+
+import pandas.util._test_decorators as td
+
+from pandas import DataFrame
+import pandas._testing as tm
+
+
+class TestCopy:
+    @pytest.mark.parametrize("attr", ["index", "columns"])
+    def test_copy_index_name_checking(self, float_frame, attr):
+        # don't want to be able to modify the index stored elsewhere after
+        # making a copy
+        ind = getattr(float_frame, attr)
+        ind.name = None
+        cp = float_frame.copy()
+        getattr(cp, attr).name = "foo"
+        assert getattr(float_frame, attr).name is None
+
+    @td.skip_copy_on_write_invalid_test
+    def test_copy_cache(self):
+        # GH#31784 _item_cache not cleared on copy causes incorrect reads after updates
+        df = DataFrame({"a": [1]})
+
+        df["x"] = [0]
+        df["a"]
+
+        df.copy()
+
+        df["a"].values[0] = -1
+
+        tm.assert_frame_equal(df, DataFrame({"a": [-1], "x": [0]}))
+
+        df["y"] = [0]
+
+        assert df["a"].values[0] == -1
+        tm.assert_frame_equal(df, DataFrame({"a": [-1], "x": [0], "y": [0]}))
+
+    def test_copy(self, float_frame, float_string_frame):
+        cop = float_frame.copy()
+        cop["E"] = cop["A"]
+        assert "E" not in float_frame
+
+        # copy objects
+        copy = float_string_frame.copy()
+        assert copy._mgr is not float_string_frame._mgr
+
+    @td.skip_array_manager_invalid_test
+    def test_copy_consolidates(self):
+        # GH#42477
+        df = DataFrame(
+            {
+                "a": np.random.default_rng(2).integers(0, 100, size=55),
+                "b": np.random.default_rng(2).integers(0, 100, size=55),
+            }
+        )
+
+        for i in range(10):
+            df.loc[:, f"n_{i}"] = np.random.default_rng(2).integers(0, 100, size=55)
+
+        assert len(df._mgr.blocks) == 11
+        result = df.copy()
+        assert len(result._mgr.blocks) == 1