import numpy as np
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import pytest
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from pandas import (
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Series,
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Timestamp,
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isna,
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)
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import pandas._testing as tm
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class TestSeriesArgsort:
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def test_argsort_axis(self):
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# GH#54257
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ser = Series(range(3))
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msg = "No axis named 2 for object type Series"
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with pytest.raises(ValueError, match=msg):
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ser.argsort(axis=2)
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def test_argsort_numpy(self, datetime_series):
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ser = datetime_series
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res = np.argsort(ser).values
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expected = np.argsort(np.array(ser))
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tm.assert_numpy_array_equal(res, expected)
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# with missing values
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ts = ser.copy()
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ts[::2] = np.nan
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msg = "The behavior of Series.argsort in the presence of NA values"
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with tm.assert_produces_warning(
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FutureWarning, match=msg, check_stacklevel=False
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):
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result = np.argsort(ts)[1::2]
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expected = np.argsort(np.array(ts.dropna()))
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tm.assert_numpy_array_equal(result.values, expected)
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def test_argsort(self, datetime_series):
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argsorted = datetime_series.argsort()
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assert issubclass(argsorted.dtype.type, np.integer)
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def test_argsort_dt64(self, unit):
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# GH#2967 (introduced bug in 0.11-dev I think)
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ser = Series(
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[Timestamp(f"201301{i:02d}") for i in range(1, 6)], dtype=f"M8[{unit}]"
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)
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assert ser.dtype == f"datetime64[{unit}]"
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shifted = ser.shift(-1)
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assert shifted.dtype == f"datetime64[{unit}]"
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assert isna(shifted[4])
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result = ser.argsort()
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expected = Series(range(5), dtype=np.intp)
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tm.assert_series_equal(result, expected)
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msg = "The behavior of Series.argsort in the presence of NA values"
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with tm.assert_produces_warning(FutureWarning, match=msg):
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result = shifted.argsort()
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expected = Series(list(range(4)) + [-1], dtype=np.intp)
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tm.assert_series_equal(result, expected)
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def test_argsort_stable(self):
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ser = Series(np.random.default_rng(2).integers(0, 100, size=10000))
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mindexer = ser.argsort(kind="mergesort")
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qindexer = ser.argsort()
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mexpected = np.argsort(ser.values, kind="mergesort")
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qexpected = np.argsort(ser.values, kind="quicksort")
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tm.assert_series_equal(mindexer.astype(np.intp), Series(mexpected))
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tm.assert_series_equal(qindexer.astype(np.intp), Series(qexpected))
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msg = (
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r"ndarray Expected type <class 'numpy\.ndarray'>, "
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r"found <class 'pandas\.core\.series\.Series'> instead"
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)
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with pytest.raises(AssertionError, match=msg):
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tm.assert_numpy_array_equal(qindexer, mindexer)
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def test_argsort_preserve_name(self, datetime_series):
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result = datetime_series.argsort()
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assert result.name == datetime_series.name
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