numpy · shoyer · Oct 23, 2018 · Oct 8, 2018 · Oct 9, 2018 · Oct 12, 2018
diff --git a/numpy/core/tests/test_overrides.py b/numpy/core/tests/test_overrides.py
@@ -16,8 +16,8 @@ def _get_overloaded_args(relevant_args):
     return args
 
 
-def _return_self(self, *args, **kwargs):
-    return self
+def _return_not_implemented(self, *args, **kwargs):
+    return NotImplemented
 
 
 class TestGetOverloadedTypesAndArgs(object):
@@ -45,7 +45,7 @@ def test_ndarray(self):
     def test_ndarray_subclasses(self):
 
         class OverrideSub(np.ndarray):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         class NoOverrideSub(np.ndarray):
             pass
@@ -70,7 +70,7 @@ class NoOverrideSub(np.ndarray):
     def test_ndarray_and_duck_array(self):
 
         class Other(object):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         array = np.array(1)
         other = Other()
@@ -86,10 +86,10 @@ class Other(object):
     def test_ndarray_subclass_and_duck_array(self):
 
         class OverrideSub(np.ndarray):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         class Other(object):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         array = np.array(1)
         subarray = np.array(1).view(OverrideSub)
@@ -103,16 +103,16 @@ class Other(object):
     def test_many_duck_arrays(self):
 
         class A(object):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         class B(A):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         class C(A):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         class D(object):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         a = A()
         b = B()
@@ -135,7 +135,7 @@ class TestNDArrayArrayFunction(object):
     def test_method(self):
 
         class SubOverride(np.ndarray):
-            __array_function__ = _return_self
+            __array_function__ = _return_not_implemented
 
         class NoOverrideSub(np.ndarray):
             pass
@@ -189,7 +189,8 @@ def __array_function__(self, func, types, args, kwargs):
         assert_(obj is original)
         assert_(func is dispatched_one_arg)
         assert_equal(set(types), {MyArray})
-        assert_equal(args, (original,))
+        # assert_equal uses the overloaded np.iscomplexobj() internally
+        assert_(args == (original,))
         assert_equal(kwargs, {})
 
     def test_not_implemented(self):

diff --git a/numpy/lib/npyio.py b/numpy/lib/npyio.py
@@ -12,6 +12,7 @@
 from . import format
 from ._datasource import DataSource
 from numpy.core.multiarray import packbits, unpackbits
+from numpy.core.overrides import array_function_dispatch
 from numpy.core._internal import recursive
 from ._iotools import (
     LineSplitter, NameValidator, StringConverter, ConverterError,
@@ -447,6 +448,11 @@ def load(file, mmap_mode=None, allow_pickle=True, fix_imports=True,
             fid.close()
 
 
+def _save_dispatcher(file, arr, allow_pickle=None, fix_imports=None):
+    return (arr,)
+
+
+@array_function_dispatch(_save_dispatcher)
 def save(file, arr, allow_pickle=True, fix_imports=True):
     """
     Save an array to a binary file in NumPy ``.npy`` format.
@@ -525,6 +531,14 @@ def save(file, arr, allow_pickle=True, fix_imports=True):
             fid.close()
 
 
+def _savez_dispatcher(file, *args, **kwds):
+    for a in args:
+        yield a
+    for v in kwds.values():
+        yield v
+
+
+@array_function_dispatch(_savez_dispatcher)
 def savez(file, *args, **kwds):
     """
     Save several arrays into a single file in uncompressed ``.npz`` format.
@@ -604,6 +618,14 @@ def savez(file, *args, **kwds):
     _savez(file, args, kwds, False)
 
 
+def _savez_compressed_dispatcher(file, *args, **kwds):
+    for a in args:
+        yield a
+    for v in kwds.values():
+        yield v
+
+
+@array_function_dispatch(_savez_compressed_dispatcher)
 def savez_compressed(file, *args, **kwds):
     """
     Save several arrays into a single file in compressed ``.npz`` format.
@@ -1154,6 +1176,13 @@ def tobytes_first(x, conv):
         return X
 
 
+def _savetxt_dispatcher(fname, X, fmt=None, delimiter=None, newline=None,
+                        header=None, footer=None, comments=None,
+                        encoding=None):
+    return (X,)
+
+
+@array_function_dispatch(_savetxt_dispatcher)
 def savetxt(fname, X, fmt='%.18e', delimiter=' ', newline='\n', header='',
             footer='', comments='# ', encoding=None):
     """

diff --git a/numpy/lib/polynomial.py b/numpy/lib/polynomial.py
@@ -14,11 +14,13 @@
 
 from numpy.core import (isscalar, abs, finfo, atleast_1d, hstack, dot, array,
                         ones)
+from numpy.core.overrides import array_function_dispatch
 from numpy.lib.twodim_base import diag, vander
 from numpy.lib.function_base import trim_zeros
 from numpy.lib.type_check import iscomplex, real, imag, mintypecode
 from numpy.linalg import eigvals, lstsq, inv
 
+
 class RankWarning(UserWarning):
     """
     Issued by `polyfit` when the Vandermonde matrix is rank deficient.
@@ -29,6 +31,12 @@ class RankWarning(UserWarning):
     """
     pass
 
+
+def _poly_dispatcher(seq_of_zeros):
+    return seq_of_zeros
+
+
+@array_function_dispatch(_poly_dispatcher)
 def poly(seq_of_zeros):
     """
     Find the coefficients of a polynomial with the given sequence of roots.
@@ -145,6 +153,12 @@ def poly(seq_of_zeros):
 
     return a
 
+
+def _roots_dispatcher(p):
+    return p
+
+
+@array_function_dispatch(_roots_dispatcher)
 def roots(p):
     """
     Return the roots of a polynomial with coefficients given in p.
@@ -229,6 +243,12 @@ def roots(p):
     roots = hstack((roots, NX.zeros(trailing_zeros, roots.dtype)))
     return roots
 
+
+def _polyint_dispatcher(p, m=None, k=None):
+    return (p,)
+
+
+@array_function_dispatch(_polyint_dispatcher)
 def polyint(p, m=1, k=None):
     """
     Return an antiderivative (indefinite integral) of a polynomial.
@@ -322,6 +342,12 @@ def polyint(p, m=1, k=None):
             return poly1d(val)
         return val
 
+
+def _polyder_dispatcher(p, m=None):
+    return (p,)
+
+
+@array_function_dispatch(_polyder_dispatcher)
 def polyder(p, m=1):
     """
     Return the derivative of the specified order of a polynomial.
@@ -390,6 +416,12 @@ def polyder(p, m=1):
         val = poly1d(val)
     return val
 
+
+def _polyfit_dispatcher(x, y, deg, rcond=None, full=None, w=None, cov=None):
+    return (x, y, w)
+
+
+@array_function_dispatch(_polyfit_dispatcher)
 def polyfit(x, y, deg, rcond=None, full=False, w=None, cov=False):
     """
     Least squares polynomial fit.
@@ -610,6 +642,11 @@ def polyfit(x, y, deg, rcond=None, full=False, w=None, cov=False):
         return c
 
 
+def _polyval_dispatcher(p, x):
+    return (p, x)
+
+
+@array_function_dispatch(_polyval_dispatcher)
 def polyval(p, x):
     """
     Evaluate a polynomial at specific values.
@@ -679,6 +716,12 @@ def polyval(p, x):
         y = y * x + p[i]
     return y
 
+
+def _binary_op_dispatcher(a1, a2):
+    return (a1, a2)
+
+
+@array_function_dispatch(_binary_op_dispatcher)
 def polyadd(a1, a2):
     """
     Find the sum of two polynomials.
@@ -739,6 +782,8 @@ def polyadd(a1, a2):
         val = poly1d(val)
     return val
 
+
+@array_function_dispatch(_binary_op_dispatcher)
 def polysub(a1, a2):
     """
     Difference (subtraction) of two polynomials.
@@ -786,6 +831,7 @@ def polysub(a1, a2):
     return val
 
 
+@array_function_dispatch(_binary_op_dispatcher)
 def polymul(a1, a2):
     """
     Find the product of two polynomials.
@@ -842,6 +888,12 @@ def polymul(a1, a2):
         val = poly1d(val)
     return val
 
+
+def _polydiv_dispatcher(u, v):
+    return (u, v)
+
+
+@array_function_dispatch(_polydiv_dispatcher)
 def polydiv(u, v):
     """
     Returns the quotient and remainder of polynomial division.