numpy · eric-wieser · May 1, 2017 · Apr 21, 2017 · May 1, 2017
diff --git a/doc/release/1.13.0-notes.rst b/doc/release/1.13.0-notes.rst
@@ -327,6 +327,11 @@ regarding "workspace" sizes, and in some places may use faster algorithms.
 This now works on empty arrays, returning 0, and can reduce over multiple axes.
 Previously, a ``ValueError`` was thrown in these cases.
 
+New ``positive`` ufunc
+----------------------
+This ufunc corresponds to unary `+`, but unlike `+` on an ndarray it will raise
+an error if array values do not support numeric operations.
+
 Changes
 =======
 

diff --git a/doc/source/reference/c-api.array.rst b/doc/source/reference/c-api.array.rst
@@ -3129,8 +3129,8 @@ Internal Flexibility
 
         **add**, **subtract**, **multiply**, **divide**,
         **remainder**, **power**, **square**, **reciprocal**,
-        **ones_like**, **sqrt**, **negative**, **absolute**,
-        **invert**, **left_shift**, **right_shift**,
+        **ones_like**, **sqrt**, **negative**, **positive**,
+        **absolute**, **invert**, **left_shift**, **right_shift**,
         **bitwise_and**, **bitwise_xor**, **bitwise_or**,
         **less**, **less_equal**, **equal**, **not_equal**,
         **greater**, **greater_equal**, **floor_divide**,

diff --git a/doc/source/reference/ufuncs.rst b/doc/source/reference/ufuncs.rst
@@ -505,6 +505,7 @@ Math operations
     true_divide
     floor_divide
     negative
+    positive
     power
     remainder
     mod

diff --git a/numpy/core/code_generators/generate_umath.py b/numpy/core/code_generators/generate_umath.py
@@ -398,6 +398,14 @@ def english_upper(s):
           TD(cmplx, f='neg'),
           TD(O, f='PyNumber_Negative'),
           ),
+'positive':
+    Ufunc(1, 1, None,
+          docstrings.get('numpy.core.umath.positive'),
+          'PyUFunc_SimpleUnaryOperationTypeResolver',
+          TD(ints+flts+timedeltaonly),
+          TD(cmplx, f='pos'),
+          TD(O, f='PyNumber_Positive'),
+          ),
 'sign':
     Ufunc(1, 1, None,
           docstrings.get('numpy.core.umath.sign'),

diff --git a/numpy/core/code_generators/ufunc_docstrings.py b/numpy/core/code_generators/ufunc_docstrings.py
@@ -2537,6 +2537,27 @@ def add_newdoc(place, name, doc):
 
     """)
 
+add_newdoc('numpy.core.umath', 'positive',
+    """
+    Numerical positive, element-wise.
+
+    Parameters
+    ----------
+    x : array_like or scalar
+        Input array.
+
+    Returns
+    -------
+    y : ndarray or scalar
+        Returned array or scalar: `y = +x`.
+
+    Notes
+    -----
+    Equivalent to `x.copy()`, but only defined for types that support
+    arithmetic.
+
+    """)
+
 add_newdoc('numpy.core.umath', 'not_equal',
     """
     Return (x1 != x2) element-wise.

diff --git a/numpy/core/src/umath/funcs.inc.src b/numpy/core/src/umath/funcs.inc.src
@@ -187,6 +187,14 @@ nc_neg@c@(@ctype@ *a, @ctype@ *r)
     return;
 }
 
+static void
+nc_pos@c@(@ctype@ *a, @ctype@ *r)
+{
+    r->real = +a->real;
+    r->imag = +a->imag;
+    return;
+}
+
 static void
 nc_sqrt@c@(@ctype@ *x, @ctype@ *r)
 {

diff --git a/numpy/core/src/umath/loops.c.src b/numpy/core/src/umath/loops.c.src
@@ -833,6 +833,12 @@ NPY_NO_EXPORT void
     }
 }
 
+NPY_NO_EXPORT void
+@TYPE@_positive(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
+{
+    UNARY_LOOP_FAST(@type@, @type@, *out = +in);
+}
+
 /**begin repeat1
  * #isa = , _avx2#
  * #ISA = , AVX2#
@@ -1184,6 +1190,15 @@ TIMEDELTA_negative(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY
     }
 }
 
+NPY_NO_EXPORT void
+TIMEDELTA_positive(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
+{
+    UNARY_LOOP {
+        const npy_timedelta in1 = *(npy_timedelta *)ip1;
+        *((npy_timedelta *)op1) = +in1;
+    }
+}
+
 NPY_NO_EXPORT void
 TIMEDELTA_absolute(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
 {
@@ -1885,6 +1900,15 @@ NPY_NO_EXPORT void
     }
 }
 
+NPY_NO_EXPORT void
+@TYPE@_positive(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
+{
+    UNARY_LOOP {
+        const @type@ in1 = *(@type@ *)ip1;
+        *((@type@ *)op1) = +in1;
+    }
+}
+
 NPY_NO_EXPORT void
 @TYPE@_sign(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
 {
@@ -2188,6 +2212,15 @@ HALF_negative(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUS
     }
 }
 
+NPY_NO_EXPORT void
+HALF_positive(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
+{
+    UNARY_LOOP {
+        const npy_half in1 = *(npy_half *)ip1;
+        *((npy_half *)op1) = +in1;
+    }
+}
+
 NPY_NO_EXPORT void
 HALF_sign(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
 {

diff --git a/numpy/core/src/umath/loops.h.src b/numpy/core/src/umath/loops.h.src
@@ -61,6 +61,9 @@ BOOL__ones_like(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UN
 NPY_NO_EXPORT void
 @S@@TYPE@__ones_like(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(data));
 
+NPY_NO_EXPORT void
+@S@@TYPE@_positive(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func));
+
 /**begin repeat2
  * #isa = , _avx2#
  */
@@ -235,6 +238,8 @@ NPY_NO_EXPORT void
 NPY_NO_EXPORT void
 @TYPE@_negative(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func));
 
+NPY_NO_EXPORT void
+@TYPE@_positive(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func));
 
 NPY_NO_EXPORT void
 @TYPE@_sign(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func));
@@ -383,6 +388,9 @@ C@TYPE@_@kind@(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNU
 NPY_NO_EXPORT void
 TIMEDELTA_negative(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func));
 
+NPY_NO_EXPORT void
+TIMEDELTA_positive(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func));
+
 NPY_NO_EXPORT void
 TIMEDELTA_absolute(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func));
 

diff --git a/numpy/core/tests/test_datetime.py b/numpy/core/tests/test_datetime.py
@@ -794,6 +794,12 @@ def test_datetime_unary(self):
             assert_equal(np.negative(tdb), tda)
             assert_equal(np.negative(tdb).dtype, tda.dtype)
 
+            # positive ufunc
+            assert_equal(np.positive(tda), tda)
+            assert_equal(np.positive(tda).dtype, tda.dtype)
+            assert_equal(np.positive(tdb), tdb)
+            assert_equal(np.positive(tdb).dtype, tdb.dtype)
+
             # absolute ufunc
             assert_equal(np.absolute(tdb), tda)
             assert_equal(np.absolute(tdb).dtype, tda.dtype)

diff --git a/numpy/core/tests/test_half.py b/numpy/core/tests/test_half.py
@@ -323,6 +323,7 @@ def test_half_ufuncs(self):
         assert_equal(np.conjugate(b), b)
         assert_equal(np.absolute(b), [2, 5, 1, 4, 3])
         assert_equal(np.negative(b), [2, -5, -1, -4, -3])
+        assert_equal(np.positive(b), b)
         assert_equal(np.sign(b), [-1, 1, 1, 1, 1])
         assert_equal(np.modf(b), ([0, 0, 0, 0, 0], b))
         assert_equal(np.frexp(b), ([-0.5, 0.625, 0.5, 0.5, 0.75], [2, 3, 1, 3, 2]))

diff --git a/numpy/core/tests/test_umath.py b/numpy/core/tests/test_umath.py
@@ -1057,6 +1057,7 @@ class TestBool(TestCase):
     def test_exceptions(self):
         a = np.ones(1, dtype=np.bool_)
         assert_raises(TypeError, np.negative, a)
+        assert_raises(TypeError, np.positive, a)
         assert_raises(TypeError, np.subtract, a, a)
 
     def test_truth_table_logical(self):
@@ -1349,6 +1350,25 @@ def test_lower_align(self):
         np.abs(np.ones_like(d), out=d)
 
 
+class TestPositive(TestCase):
+    def test_valid(self):
+        valid_dtypes = [int, float, complex, object]
+        for dtype in valid_dtypes:
+            x = np.arange(5, dtype=dtype)
+            result = np.positive(x)
+            assert_equal(x, result, err_msg=str(dtype))
+
+    def test_invalid(self):
+        with assert_raises(TypeError):
+            np.positive(True)
+        with assert_raises(TypeError):
+            np.positive(np.datetime64('2000-01-01'))
+        with assert_raises(TypeError):
+            np.positive(np.array(['foo'], dtype=str))
+        with assert_raises(TypeError):
+            np.positive(np.array(['bar'], dtype=object))
+
+
 class TestSpecialMethods(TestCase):
     def test_wrap(self):
 

diff --git a/numpy/lib/mixins.py b/numpy/lib/mixins.py
@@ -70,8 +70,8 @@ class NDArrayOperatorsMixin(object):
     implement.
 
     This class does not yet implement the special operators corresponding
-    to ``divmod``, unary ``+`` or ``matmul`` (``@``), because these operation
-    do not yet have corresponding NumPy ufuncs.
+    to ``divmod`` or ``matmul`` (``@``), because these operation do not yet
+    have corresponding NumPy ufuncs.
 
     It is useful for writing classes that do not inherit from `numpy.ndarray`,
     but that should support arithmetic and numpy universal functions like
@@ -174,5 +174,6 @@ def __repr__(self):
 
     # unary methods
     __neg__ = _unary_method(um.negative, 'neg')
+    __pos__ = _unary_method(um.positive, 'pos')
     __abs__ = _unary_method(um.absolute, 'abs')
     __invert__ = _unary_method(um.invert, 'invert')
diff --git a/numpy/lib/tests/test_mixins.py b/numpy/lib/tests/test_mixins.py
@@ -143,7 +143,7 @@ def test_unary_methods(self):
         array = np.array([-1, 0, 1, 2])
         array_like = ArrayLike(array)
         for op in [operator.neg,
-                   # pos is not yet implemented
+                   operator.pos,
                    abs,
                    operator.invert]:
             _assert_equal_type_and_value(op(array_like), ArrayLike(op(array)))