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.venv/Lib/site-packages/pandas/tests/frame/indexing/test_lookup.py

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+import numpy as np
+import pytest
+
+from pandas import (
+    DataFrame,
+    Series,
+)
+import pandas._testing as tm
+
+
+class TestLookup:
+    def test_lookup_float(self, float_frame):
+        df = float_frame
+        rows = list(df.index) * len(df.columns)
+        cols = list(df.columns) * len(df.index)
+        with tm.assert_produces_warning(FutureWarning):
+            result = df.lookup(rows, cols)
+
+        expected = np.array([df.loc[r, c] for r, c in zip(rows, cols)])
+        tm.assert_numpy_array_equal(result, expected)
+
+    def test_lookup_mixed(self, float_string_frame):
+        df = float_string_frame
+        rows = list(df.index) * len(df.columns)
+        cols = list(df.columns) * len(df.index)
+        with tm.assert_produces_warning(FutureWarning):
+            result = df.lookup(rows, cols)
+
+        expected = np.array(
+            [df.loc[r, c] for r, c in zip(rows, cols)], dtype=np.object_
+        )
+        tm.assert_almost_equal(result, expected)
+
+    def test_lookup_bool(self):
+        df = DataFrame(
+            {
+                "label": ["a", "b", "a", "c"],
+                "mask_a": [True, True, False, True],
+                "mask_b": [True, False, False, False],
+                "mask_c": [False, True, False, True],
+            }
+        )
+        with tm.assert_produces_warning(FutureWarning):
+            df["mask"] = df.lookup(df.index, "mask_" + df["label"])
+
+        exp_mask = np.array(
+            [df.loc[r, c] for r, c in zip(df.index, "mask_" + df["label"])]
+        )
+
+        tm.assert_series_equal(df["mask"], Series(exp_mask, name="mask"))
+        assert df["mask"].dtype == np.bool_
+
+    def test_lookup_raises(self, float_frame):
+        with pytest.raises(KeyError, match="'One or more row labels was not found'"):
+            with tm.assert_produces_warning(FutureWarning):
+                float_frame.lookup(["xyz"], ["A"])
+
+        with pytest.raises(KeyError, match="'One or more column labels was not found'"):
+            with tm.assert_produces_warning(FutureWarning):
+                float_frame.lookup([float_frame.index[0]], ["xyz"])
+
+        with pytest.raises(ValueError, match="same size"):
+            with tm.assert_produces_warning(FutureWarning):
+                float_frame.lookup(["a", "b", "c"], ["a"])
+
+    def test_lookup_requires_unique_axes(self):
+        # GH#33041 raise with a helpful error message
+        df = DataFrame(np.random.randn(6).reshape(3, 2), columns=["A", "A"])
+
+        rows = [0, 1]
+        cols = ["A", "A"]
+
+        # homogeneous-dtype case
+        with pytest.raises(ValueError, match="requires unique index and columns"):
+            with tm.assert_produces_warning(FutureWarning):
+                df.lookup(rows, cols)
+        with pytest.raises(ValueError, match="requires unique index and columns"):
+            with tm.assert_produces_warning(FutureWarning):
+                df.T.lookup(cols, rows)
+
+        # heterogeneous dtype
+        df["B"] = 0
+        with pytest.raises(ValueError, match="requires unique index and columns"):
+            with tm.assert_produces_warning(FutureWarning):
+                df.lookup(rows, cols)
+
+
+def test_lookup_deprecated():
+    # GH#18262
+    df = DataFrame(
+        {"col": ["A", "A", "B", "B"], "A": [80, 23, np.nan, 22], "B": [80, 55, 76, 67]}
+    )
+    with tm.assert_produces_warning(FutureWarning):
+        df.lookup(df.index, df["col"])