ENH: Implement rounding for floating dtype array #38844

doc/source/whatsnew/v1.3.0.rst

@@ -139,6 +139,7 @@ Other enhancements
 - :meth:`pandas.read_stata` and :class:`StataReader` support reading data from compressed files.
 - Add support for parsing ``ISO 8601``-like timestamps with negative signs to :meth:`pandas.Timedelta` (:issue:`37172`)
 - Add support for unary operators in :class:`FloatingArray` (:issue:`38749`)
+- :meth:`round` being enabled for the nullable integer and floating dtypes (:issue:`38844`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/arrays/numeric.py

@@ -6,6 +6,7 @@
     TYPE_CHECKING,
     Any,
     List,
+    TypeVar,
     Union,
 )
 
@@ -15,6 +16,7 @@
     Timedelta,
     missing as libmissing,
 )
+from pandas.compat.numpy import function as nv
 from pandas.errors import AbstractMethodError
 
 from pandas.core.dtypes.common import (
@@ -34,6 +36,8 @@
 if TYPE_CHECKING:
     import pyarrow
 
+T = TypeVar("T", bound="NumericArray")
+
 
 class NumericDtype(BaseMaskedDtype):
     def __from_arrow__(
@@ -208,3 +212,31 @@ def __pos__(self):
 
     def __abs__(self):
         return type(self)(abs(self._data), self._mask.copy())
+
+    def round(self: T, decimals: int = 0, *args, **kwargs) -> T:
+        """
+        Round each value in the array a to the given number of decimals.
+
+        Parameters
+        ----------
+        decimals : int, default 0
+            Number of decimal places to round to. If decimals is negative,
+            it specifies the number of positions to the left of the decimal point.
+        *args, **kwargs
+            Additional arguments and keywords have no effect but might be
+            accepted for compatibility with NumPy.
+
+        Returns
+        -------
+        NumericArray
+            Rounded values of the NumericArray.
+
+        See Also
+        --------
+        numpy.around : Round values of an np.array.
+        DataFrame.round : Round values of a DataFrame.
+        Series.round : Round values of a Series.
+        """
+        nv.validate_round(args, kwargs)
+        values = np.round(self._data, decimals=decimals, **kwargs)
+        return type(self)(values, self._mask.copy())

pandas/tests/arrays/masked/test_function.py

@@ -0,0 +1,44 @@
+import numpy as np
+import pytest
+
+from pandas.core.dtypes.common import is_integer_dtype
+
+import pandas as pd
+import pandas._testing as tm
+
+arrays = [pd.array([1, 2, 3, None], dtype=dtype) for dtype in tm.ALL_EA_INT_DTYPES]
+arrays += [
+    pd.array([0.141, -0.268, 5.895, None], dtype=dtype) for dtype in tm.FLOAT_EA_DTYPES
+]
+
+
+@pytest.fixture(params=arrays, ids=[a.dtype.name for a in arrays])
+def data(request):
+    return request.param
+
+
+@pytest.fixture()
+def numpy_dtype(data):
+    # For integer dtype, the numpy conversion must be done to float
+    if is_integer_dtype(data):
+        numpy_dtype = float
+    else:
+        numpy_dtype = data.dtype.type
+    return numpy_dtype
+
+
+def test_round(data, numpy_dtype):
+    # No arguments
+    result = data.round()
+    expected = pd.array(
+        np.round(data.to_numpy(dtype=numpy_dtype, na_value=None)), dtype=data.dtype
+    )
+    tm.assert_extension_array_equal(result, expected)
+
+    # Decimals argument
+    result = data.round(decimals=2)
+    expected = pd.array(
+        np.round(data.to_numpy(dtype=numpy_dtype, na_value=None), decimals=2),
+        dtype=data.dtype,
+    )
+    tm.assert_extension_array_equal(result, expected)

pandas/tests/series/methods/test_round.py

@@ -16,33 +16,41 @@ def test_round(self, datetime_series):
         tm.assert_series_equal(result, expected)
         assert result.name == datetime_series.name
 
-    def test_round_numpy(self):
+    def test_round_numpy(self, any_float_allowed_nullable_dtype):
         # See GH#12600
-        ser = Series([1.53, 1.36, 0.06])
+        ser = Series([1.53, 1.36, 0.06], dtype=any_float_allowed_nullable_dtype)
         out = np.round(ser, decimals=0)
-        expected = Series([2.0, 1.0, 0.0])
+        expected = Series([2.0, 1.0, 0.0], dtype=any_float_allowed_nullable_dtype)
         tm.assert_series_equal(out, expected)
 
         msg = "the 'out' parameter is not supported"
         with pytest.raises(ValueError, match=msg):
             np.round(ser, decimals=0, out=ser)
 
-    def test_round_numpy_with_nan(self):
+    def test_round_numpy_with_nan(self, any_float_allowed_nullable_dtype):
         # See GH#14197
-        ser = Series([1.53, np.nan, 0.06])
+        ser = Series([1.53, np.nan, 0.06], dtype=any_float_allowed_nullable_dtype)
         with tm.assert_produces_warning(None):
             result = ser.round()
-        expected = Series([2.0, np.nan, 0.0])
+        expected = Series([2.0, np.nan, 0.0], dtype=any_float_allowed_nullable_dtype)
         tm.assert_series_equal(result, expected)
 
-    def test_round_builtin(self):
-        ser = Series([1.123, 2.123, 3.123], index=range(3))
+    def test_round_builtin(self, any_float_allowed_nullable_dtype):
+        ser = Series(
+            [1.123, 2.123, 3.123],
+            index=range(3),
+            dtype=any_float_allowed_nullable_dtype,
+        )
         result = round(ser)
-        expected_rounded0 = Series([1.0, 2.0, 3.0], index=range(3))
+        expected_rounded0 = Series(
+            [1.0, 2.0, 3.0], index=range(3), dtype=any_float_allowed_nullable_dtype
+        )
         tm.assert_series_equal(result, expected_rounded0)
 
         decimals = 2
-        expected_rounded = Series([1.12, 2.12, 3.12], index=range(3))
+        expected_rounded = Series(
+            [1.12, 2.12, 3.12], index=range(3), dtype=any_float_allowed_nullable_dtype
+        )
         result = round(ser, decimals)
         tm.assert_series_equal(result, expected_rounded)