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