Change UInt64Index._na_value from 0 to np.nan (#18401)

doc/source/whatsnew/v0.22.0.txt

@@ -52,6 +52,7 @@ Backwards incompatible API changes
 
 - :func:`Series.fillna` now raises a ``TypeError`` instead of a ``ValueError`` when passed a list, tuple or DataFrame as a ``value`` (:issue:`18293`)
 - :func:`pandas.DataFrame.merge` no longer casts a ``float`` column to ``object`` when merging on ``int`` and ``float`` columns (:issue:`16572`)
+- The default NA value for :class:`UInt64Index` has changed from 0 to ``NaN``, which impacts methods that mask with NA, such as ``UInt64Index.where()`` (:issue:`18398`)
 -
 
 
@@ -129,7 +130,7 @@ Bug Fixes
 Conversion
 ^^^^^^^^^^
 
--
+- Bug in :class:`Index` constructor with `dtype='uint64'` where int-like floats were not coerced to :class:`UInt64Index` (:issue:`18400`)
 -
 -
 

pandas/core/indexes/base.py

@@ -251,7 +251,7 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
                             # then coerce to integer.
                             try:
                                 return cls._try_convert_to_int_index(
-                                    data, copy, name)
+                                    data, copy, name, dtype)
                             except ValueError:
                                 pass
 
@@ -307,7 +307,7 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
                 if inferred == 'integer':
                     try:
                         return cls._try_convert_to_int_index(
-                            subarr, copy, name)
+                            subarr, copy, name, dtype)
                     except ValueError:
                         pass
 
@@ -664,7 +664,7 @@ def ravel(self, order='C'):
 
     # construction helpers
     @classmethod
-    def _try_convert_to_int_index(cls, data, copy, name):
+    def _try_convert_to_int_index(cls, data, copy, name, dtype):
         """
         Attempt to convert an array of data into an integer index.
 
@@ -685,15 +685,18 @@ def _try_convert_to_int_index(cls, data, copy, name):
         """
 
         from .numeric import Int64Index, UInt64Index
-        try:
-            res = data.astype('i8', copy=False)
-            if (res == data).all():
-                return Int64Index(res, copy=copy, name=name)
-        except (OverflowError, TypeError, ValueError):
-            pass
+        if not is_unsigned_integer_dtype(dtype):
+            # skip int64 conversion attempt if uint-like dtype is passed, as
+            # this could return Int64Index when UInt64Index is what's desrired
+            try:
+                res = data.astype('i8', copy=False)
+                if (res == data).all():
+                    return Int64Index(res, copy=copy, name=name)
+            except (OverflowError, TypeError, ValueError):
+                pass
 
-        # Conversion to int64 failed (possibly due to
-        # overflow), so let's try now with uint64.
+        # Conversion to int64 failed (possibly due to overflow) or was skipped,
+        # so let's try now with uint64.
         try:
             res = data.astype('u8', copy=False)
             if (res == data).all():

pandas/core/indexes/numeric.py

@@ -216,7 +216,6 @@ class UInt64Index(NumericIndex):
     _inner_indexer = libjoin.inner_join_indexer_uint64
     _outer_indexer = libjoin.outer_join_indexer_uint64
     _can_hold_na = False
-    _na_value = 0
     _engine_type = libindex.UInt64Engine
     _default_dtype = np.uint64
 

pandas/tests/indexes/common.py

@@ -9,8 +9,7 @@
 
 from pandas import (Series, Index, Float64Index, Int64Index, UInt64Index,
                     RangeIndex, MultiIndex, CategoricalIndex, DatetimeIndex,
-                    TimedeltaIndex, PeriodIndex, IntervalIndex,
-                    notna, isna)
+                    TimedeltaIndex, PeriodIndex, IntervalIndex, isna)
 from pandas.core.indexes.base import InvalidIndexError
 from pandas.core.indexes.datetimelike import DatetimeIndexOpsMixin
 from pandas.core.dtypes.common import needs_i8_conversion
@@ -529,31 +528,20 @@ def test_numpy_repeat(self):
         tm.assert_raises_regex(ValueError, msg, np.repeat,
                                i, rep, axis=0)
 
-    def test_where(self):
+    @pytest.mark.parametrize('klass', [list, tuple, np.array, Series])
+    def test_where(self, klass):
         i = self.create_index()
-        result = i.where(notna(i))
+
+        cond = [True] * len(i)
+        result = i.where(klass(cond))
         expected = i
         tm.assert_index_equal(result, expected)
 
-        _nan = i._na_value
         cond = [False] + [True] * len(i[1:])
-        expected = pd.Index([_nan] + i[1:].tolist(), dtype=i.dtype)
-
-        result = i.where(cond)
+        expected = pd.Index([i._na_value] + i[1:].tolist(), dtype=i.dtype)
+        result = i.where(klass(cond))
         tm.assert_index_equal(result, expected)
 
-    def test_where_array_like(self):
-        i = self.create_index()
-
-        _nan = i._na_value
-        cond = [False] + [True] * (len(i) - 1)
-        klasses = [list, tuple, np.array, pd.Series]
-        expected = pd.Index([_nan] + i[1:].tolist(), dtype=i.dtype)
-
-        for klass in klasses:
-            result = i.where(klass(cond))
-            tm.assert_index_equal(result, expected)
-
     def test_setops_errorcases(self):
         for name, idx in compat.iteritems(self.indices):
             # # non-iterable input

pandas/tests/indexes/period/test_period.py

@@ -61,27 +61,18 @@ def test_pickle_round_trip(self):
             result = tm.round_trip_pickle(idx)
             tm.assert_index_equal(result, idx)
 
-    def test_where(self):
+    @pytest.mark.parametrize('klass', [list, tuple, np.array, Series])
+    def test_where(self, klass):
         i = self.create_index()
-        result = i.where(notna(i))
+        cond = [True] * len(i)
         expected = i
+        result = i.where(klass(cond))
         tm.assert_index_equal(result, expected)
 
-        i2 = pd.PeriodIndex([pd.NaT, pd.NaT] + i[2:].tolist(),
-                            freq='D')
-        result = i.where(notna(i2))
-        expected = i2
-        tm.assert_index_equal(result, expected)
-
-    def test_where_array_like(self):
-        i = self.create_index()
         cond = [False] + [True] * (len(i) - 1)
-        klasses = [list, tuple, np.array, Series]
-        expected = pd.PeriodIndex([pd.NaT] + i[1:].tolist(), freq='D')
-
-        for klass in klasses:
-            result = i.where(klass(cond))
-            tm.assert_index_equal(result, expected)
+        expected = PeriodIndex([NaT] + i[1:].tolist(), freq='D')
+        result = i.where(klass(cond))
+        tm.assert_index_equal(result, expected)
 
     def test_where_other(self):
 

pandas/tests/indexes/test_base.py

@@ -5,6 +5,7 @@
 from datetime import datetime, timedelta
 
 import pandas.util.testing as tm
+from pandas.core.dtypes.common import is_unsigned_integer_dtype
 from pandas.core.indexes.api import Index, MultiIndex
 from pandas.tests.indexes.common import Base
 
@@ -14,7 +15,7 @@
 import numpy as np
 
 from pandas import (period_range, date_range, Series,
-                    DataFrame, Float64Index, Int64Index,
+                    DataFrame, Float64Index, Int64Index, UInt64Index,
                     CategoricalIndex, DatetimeIndex, TimedeltaIndex,
                     PeriodIndex, isna)
 from pandas.core.index import _get_combined_index, _ensure_index_from_sequences
@@ -201,6 +202,20 @@ def __array__(self, dtype=None):
             result = pd.Index(ArrayLike(array))
             tm.assert_index_equal(result, expected)
 
+    @pytest.mark.parametrize('dtype', [
+        int, 'int64', 'int32', 'int16', 'int8', 'uint64', 'uint32',
+        'uint16', 'uint8'])
+    def test_constructor_int_dtype_float(self, dtype):
+        # GH 18400
+        if is_unsigned_integer_dtype(dtype):
+            index_type = UInt64Index
+        else:
+            index_type = Int64Index
+
+        expected = index_type([0, 1, 2, 3])
+        result = Index([0., 1., 2., 3.], dtype=dtype)
+        tm.assert_index_equal(result, expected)
+
     def test_constructor_int_dtype_nan(self):
         # see gh-15187
         data = [np.nan]

pandas/tests/indexes/test_category.py

@@ -11,7 +11,7 @@
 
 import numpy as np
 
-from pandas import Categorical, IntervalIndex, compat, notna
+from pandas import Categorical, IntervalIndex, compat
 from pandas.util.testing import assert_almost_equal
 import pandas.core.config as cf
 import pandas as pd
@@ -269,28 +269,19 @@ def f(x):
                                   ordered=False)
         tm.assert_index_equal(result, exp)
 
-    def test_where(self):
+    @pytest.mark.parametrize('klass', [list, tuple, np.array, pd.Series])
+    def test_where(self, klass):
         i = self.create_index()
-        result = i.where(notna(i))
+        cond = [True] * len(i)
         expected = i
+        result = i.where(klass(cond))
         tm.assert_index_equal(result, expected)
 
-        i2 = pd.CategoricalIndex([np.nan, np.nan] + i[2:].tolist(),
-                                 categories=i.categories)
-        result = i.where(notna(i2))
-        expected = i2
-        tm.assert_index_equal(result, expected)
-
-    def test_where_array_like(self):
-        i = self.create_index()
         cond = [False] + [True] * (len(i) - 1)
-        klasses = [list, tuple, np.array, pd.Series]
-        expected = pd.CategoricalIndex([np.nan] + i[1:].tolist(),
-                                       categories=i.categories)
-
-        for klass in klasses:
-            result = i.where(klass(cond))
-            tm.assert_index_equal(result, expected)
+        expected = CategoricalIndex([np.nan] + i[1:].tolist(),
+                                    categories=i.categories)
+        result = i.where(klass(cond))
+        tm.assert_index_equal(result, expected)
 
     def test_append(self):
 

pandas/tests/indexes/test_interval.py

@@ -348,20 +348,19 @@ def test_astype(self, closed):
         expected = pd.Categorical(idx, ordered=True)
         tm.assert_categorical_equal(result, expected)
 
-    def test_where(self, closed):
-        expected = self.create_index(closed=closed)
-        result = expected.where(expected.notna())
+    @pytest.mark.parametrize('klass', [list, tuple, np.array, pd.Series])
+    def test_where(self, closed, klass):
+        idx = self.create_index(closed=closed)
+        cond = [True] * len(idx)
+        expected = idx
+        result = expected.where(klass(cond))
         tm.assert_index_equal(result, expected)
 
-        idx = IntervalIndex.from_breaks([1, 2], closed=closed)
-        result = idx.where([True, False])
-        expected = IntervalIndex.from_intervals(
-            [Interval(1.0, 2.0, closed=closed), np.nan])
+        cond = [False] + [True] * len(idx[1:])
+        expected = IntervalIndex([np.nan] + idx[1:].tolist())
+        result = idx.where(klass(cond))
         tm.assert_index_equal(result, expected)
 
-    def test_where_array_like(self):
-        pass
-
     def test_delete(self, closed):
         expected = IntervalIndex.from_breaks([1, 2], closed=closed)
         result = self.create_index(closed=closed).delete(0)

pandas/tests/indexes/test_numeric.py

@@ -7,7 +7,7 @@
 
 import numpy as np
 
-from pandas import (date_range, notna, Series, Index, Float64Index,
+from pandas import (date_range, Series, Index, Float64Index,
                     Int64Index, UInt64Index, RangeIndex)
 
 import pandas.util.testing as tm
@@ -175,6 +175,18 @@ def test_modulo(self):
         expected = Index(index.values % 2)
         tm.assert_index_equal(index % 2, expected)
 
+    @pytest.mark.parametrize('klass', [list, tuple, np.array, Series])
+    def test_where(self, klass):
+        i = self.create_index()
+        cond = [True] * len(i)
+        expected = i
+        result = i.where(klass(cond))
+
+        cond = [False] + [True] * (len(i) - 1)
+        expected = Float64Index([i._na_value] + i[1:].tolist())
+        result = i.where(klass(cond))
+        tm.assert_index_equal(result, expected)
+
 
 class TestFloat64Index(Numeric):
     _holder = Float64Index
@@ -726,31 +738,6 @@ def test_coerce_list(self):
         arr = Index([1, 2, 3, 4], dtype=object)
         assert isinstance(arr, Index)
 
-    def test_where(self):
-        i = self.create_index()
-        result = i.where(notna(i))
-        expected = i
-        tm.assert_index_equal(result, expected)
-
-        _nan = i._na_value
-        cond = [False] + [True] * len(i[1:])
-        expected = pd.Index([_nan] + i[1:].tolist())
-
-        result = i.where(cond)
-        tm.assert_index_equal(result, expected)
-
-    def test_where_array_like(self):
-        i = self.create_index()
-
-        _nan = i._na_value
-        cond = [False] + [True] * (len(i) - 1)
-        klasses = [list, tuple, np.array, pd.Series]
-        expected = pd.Index([_nan] + i[1:].tolist())
-
-        for klass in klasses:
-            result = i.where(klass(cond))
-            tm.assert_index_equal(result, expected)
-
     def test_get_indexer(self):
         target = Int64Index(np.arange(10))
         indexer = self.index.get_indexer(target)

pandas/tests/indexes/test_range.py

@@ -10,7 +10,7 @@
 
 import numpy as np
 
-from pandas import (isna, notna, Series, Index, Float64Index,
+from pandas import (isna, Series, Index, Float64Index,
                     Int64Index, RangeIndex)
 
 import pandas.util.testing as tm
@@ -934,31 +934,6 @@ def test_len_specialised(self):
             i = RangeIndex(0, 5, step)
             assert len(i) == 0
 
-    def test_where(self):
-        i = self.create_index()
-        result = i.where(notna(i))
-        expected = i
-        tm.assert_index_equal(result, expected)
-
-        _nan = i._na_value
-        cond = [False] + [True] * len(i[1:])
-        expected = pd.Index([_nan] + i[1:].tolist())
-
-        result = i.where(cond)
-        tm.assert_index_equal(result, expected)
-
-    def test_where_array_like(self):
-        i = self.create_index()
-
-        _nan = i._na_value
-        cond = [False] + [True] * (len(i) - 1)
-        klasses = [list, tuple, np.array, pd.Series]
-        expected = pd.Index([_nan] + i[1:].tolist())
-
-        for klass in klasses:
-            result = i.where(klass(cond))
-            tm.assert_index_equal(result, expected)
-
     def test_append(self):
         # GH16212
         RI = RangeIndex