Deprecate is_SchemeMorphism, is_SchemeTopologicalPoint

src/sage/categories/schemes.py

@@ -24,6 +24,11 @@
 from sage.categories.fields import Fields
 from sage.categories.homsets import HomsetsCategory
 from sage.misc.abstract_method import abstract_method
+from sage.misc.lazy_import import lazy_import
+
+lazy_import('sage.categories.map', 'Map')
+lazy_import('sage.schemes.generic.morphism', 'SchemeMorphism')
+lazy_import('sage.schemes.generic.scheme', 'Scheme')
 
 
 class Schemes(Category):
@@ -139,15 +144,10 @@ def _call_(self, x):
                       From: Integer Ring
                       To:   Rational Field
         """
-        from sage.schemes.generic.scheme import Scheme
-        if isinstance(x, Scheme):
-            return x
-        from sage.schemes.generic.morphism import is_SchemeMorphism
-        if is_SchemeMorphism(x):
+        if isinstance(x, (SchemeMorphism, Scheme)):
             return x
         from sage.categories.commutative_rings import CommutativeRings
         from sage.schemes.generic.spec import Spec
-        from sage.categories.map import Map
         if x in CommutativeRings():
             return Spec(x)
         elif isinstance(x, Map) and x.category_for().is_subcategory(Rings()):

src/sage/schemes/affine/affine_point.py

@@ -22,8 +22,9 @@
 # ****************************************************************************
 
 from sage.categories.number_fields import NumberFields
+from sage.misc.lazy_import import lazy_import
 from sage.rings.integer_ring import ZZ
-from sage.schemes.generic.morphism import SchemeMorphism_point, SchemeMorphism, is_SchemeMorphism
+from sage.schemes.generic.morphism import SchemeMorphism_point, SchemeMorphism
 from sage.structure.sequence import Sequence
 
 _NumberFields = NumberFields()
@@ -69,7 +70,7 @@ def __init__(self, X, v, check=True):
         SchemeMorphism.__init__(self, X)
         if check:
             from sage.categories.commutative_rings import CommutativeRings
-            if is_SchemeMorphism(v):
+            if isinstance(v, SchemeMorphism):
                 v = list(v)
             else:
                 try:

src/sage/schemes/elliptic_curves/ell_point.py

@@ -130,7 +130,6 @@
 from sage.rings.real_mpfr import RealField, RR
 from sage.schemes.curves.projective_curve import Hasse_bounds
 from sage.schemes.elliptic_curves.constructor import EllipticCurve
-from sage.schemes.generic.morphism import is_SchemeMorphism
 from sage.schemes.projective.projective_point import (SchemeMorphism_point_projective_ring,
                                                       SchemeMorphism_point_abelian_variety_field)
 from sage.structure.coerce_actions import IntegerMulAction
@@ -139,6 +138,7 @@
 from sage.structure.sequence import Sequence
 
 lazy_import('sage.rings.padics.factory', 'Qp')
+lazy_import('sage.schemes.generic.morphism', 'SchemeMorphism')
 
 try:
     from sage.libs.pari.all import pari, PariError
@@ -175,7 +175,8 @@ def curve(self):
             sage: K.<a> = NumberField(x^2 - 3,'a')                                      # needs sage.rings.number_field
             sage: P = E.base_extend(K)(1, a)                                            # needs sage.rings.number_field
             sage: P.scheme()                                                            # needs sage.rings.number_field
-            Elliptic Curve defined by y^2 = x^3 + x + 1 over Number Field in a with defining polynomial x^2 - 3
+            Elliptic Curve defined by y^2 = x^3 + x + 1 over
+             Number Field in a with defining polynomial x^2 - 3
         """
         return self.scheme()
 
@@ -290,7 +291,7 @@ def __init__(self, curve, v, check=True):
         """
         point_homset = curve.point_homset()
         R = point_homset.value_ring()
-        if is_SchemeMorphism(v) or isinstance(v, EllipticCurvePoint_field):
+        if isinstance(v, SchemeMorphism):
             v = list(v)
         elif v == 0:
             v = (R.zero(), R.one(), R.zero())

src/sage/schemes/generic/divisor.py

@@ -42,14 +42,15 @@
 #*******************************************************************************
 
 from sage.misc.latex import latex
+from sage.misc.lazy_import import lazy_import
 from sage.misc.repr import repr_lincomb
 from sage.misc.search import search
 from sage.rings.integer_ring import ZZ
-from sage.structure.formal_sum import FormalSum
-
-from .morphism import is_SchemeMorphism
 from sage.schemes.affine.affine_space import AffineSpace_generic
 from sage.schemes.projective.projective_space import ProjectiveSpace_ring
+from sage.structure.formal_sum import FormalSum
+
+lazy_import('sage.schemes.generic.morphism', 'SchemeMorphism')
 
 
 def CurvePointToIdeal(C,P):
@@ -356,7 +357,7 @@ def __init__(self, v, parent=None, check=True, reduce=True):
                 else:
                     n = ZZ(1)
                     I = t
-                if is_SchemeMorphism(I):
+                if isinstance(I, SchemeMorphism):
                     I = CurvePointToIdeal(C,I)
                 else:
                     know_points = False

src/sage/schemes/generic/glue.py

@@ -8,10 +8,13 @@
 #                  http://www.gnu.org/licenses/
 #*******************************************************************************
 
-from . import morphism
-from . import scheme
+from sage.misc.lazy_import import lazy_import
+from sage.schemes.generic.scheme import Scheme
 
-class GluedScheme(scheme.Scheme):
+lazy_import('sage.schemes.generic.morphism', 'SchemeMorphism')
+
+
+class GluedScheme(Scheme):
     r"""
     INPUT:
 
@@ -44,9 +47,9 @@ class GluedScheme(scheme.Scheme):
     """
     def __init__(self, f, g, check=True):
         if check:
-            if not morphism.is_SchemeMorphism(f):
+            if not isinstance(f, SchemeMorphism):
                 raise TypeError("f (=%s) must be a scheme morphism" % f)
-            if not morphism.is_SchemeMorphism(g):
+            if not isinstance(g, SchemeMorphism):
                 raise TypeError("g (=%s) must be a scheme morphism" % g)
             if f.domain() != g.domain():
                 raise ValueError("f (=%s) and g (=%s) must have the same domain" % (f,g))

src/sage/schemes/generic/morphism.py

@@ -74,20 +74,20 @@
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-
 import operator
-from sage.structure.element import Element, parent, coercion_model
+
 from sage.arith.power import generic_power
-from sage.structure.richcmp import richcmp
-from sage.structure.sequence import Sequence
 from sage.categories.homset import Homset, Hom, End
-from sage.rings.fraction_field_element import FractionFieldElement
-from sage.rings.fraction_field import FractionField_generic
 from sage.categories.map import FormalCompositeMap, Map
+from sage.categories.morphism import SetMorphism
 from sage.misc.constant_function import ConstantFunction
 from sage.misc.lazy_attribute import lazy_attribute
-from sage.categories.morphism import SetMorphism
+from sage.rings.fraction_field import FractionField_generic
+from sage.rings.fraction_field_element import FractionFieldElement
 from sage.schemes.generic.algebraic_scheme import AlgebraicScheme_subscheme
+from sage.structure.element import Element, parent, coercion_model
+from sage.structure.richcmp import richcmp
+from sage.structure.sequence import Sequence
 
 
 def is_SchemeMorphism(f):
@@ -111,13 +111,17 @@ def is_SchemeMorphism(f):
           Defn: Defined on coordinates by sending (x, y) to (y, x^2 + y)
         sage: from sage.schemes.generic.morphism import is_SchemeMorphism
         sage: is_SchemeMorphism(f)
+        doctest:warning...
+        DeprecationWarning: The function is_SchemeMorphism is deprecated;
+        use 'isinstance(..., SchemeMorphism)' instead.
+        See https://github.com/sagemath/sage/issues/38296 for details.
         True
     """
-    try:
-        from sage.schemes.elliptic_curves.ell_point import EllipticCurvePoint_field
-    except ImportError:
-        EllipticCurvePoint_field = ()
-    return isinstance(f, (SchemeMorphism, EllipticCurvePoint_field))
+    from sage.misc.superseded import deprecation
+    deprecation(38296,
+                "The function is_SchemeMorphism is deprecated; "
+                "use 'isinstance(..., SchemeMorphism)' instead.")
+    return isinstance(f, SchemeMorphism)
 
 
 class SchemeMorphism(Element):

src/sage/schemes/generic/point.py

@@ -73,6 +73,10 @@
 ########################################################
 
 def is_SchemeTopologicalPoint(x):
+    from sage.misc.superseded import deprecation
+    deprecation(38296,
+                "The function is_SchemeTopologicalPoint is deprecated; "
+                "use 'isinstance(..., SchemeTopologicalPoint)' instead.")
     return isinstance(x, SchemeTopologicalPoint)
 
 class SchemeTopologicalPoint(SchemePoint):

src/sage/schemes/generic/scheme.py

@@ -19,15 +19,16 @@
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from sage.structure.parent import Parent
+from sage.categories.commutative_rings import CommutativeRings
 from sage.misc.cachefunc import cached_method
 from sage.misc.lazy_import import lazy_import
-from sage.rings.integer_ring import ZZ
-from sage.categories.commutative_rings import CommutativeRings
 from sage.rings.ideal import Ideal_generic
-from sage.structure.unique_representation import UniqueRepresentation
+from sage.rings.integer_ring import ZZ
 from sage.schemes.generic.point import SchemeTopologicalPoint_prime_ideal
+from sage.structure.parent import Parent
+from sage.structure.unique_representation import UniqueRepresentation
 
+lazy_import('sage.schemes.generic.morphism', 'SchemeMorphism')
 lazy_import('sage.schemes.elliptic_curves.ell_generic', 'EllipticCurve_generic', as_='EllipticCurve')
 
 
@@ -104,15 +105,14 @@ def __init__(self, X=None, category=None):
             sage: X = Spec(RmodI)
             sage: TestSuite(X).run()                                                    # needs sage.libs.singular
         """
-        from sage.schemes.generic.morphism import is_SchemeMorphism
         from sage.categories.map import Map
         from sage.categories.rings import Rings
 
         if X is None:
             self._base_ring = ZZ
         elif isinstance(X, Scheme):
             self._base_scheme = X
-        elif is_SchemeMorphism(X):
+        elif isinstance(X, SchemeMorphism):
             self._base_morphism = X
         elif X in CommutativeRings():
             self._base_ring = X

src/sage/schemes/hyperelliptic_curves/jacobian_homset.py

@@ -42,14 +42,15 @@
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from sage.rings.polynomial.polynomial_ring_constructor import PolynomialRing
-from sage.rings.integer_ring import ZZ
+from sage.misc.lazy_import import lazy_import
 from sage.rings.integer import Integer
+from sage.rings.integer_ring import ZZ
 from sage.rings.polynomial.polynomial_element import Polynomial
-
+from sage.rings.polynomial.polynomial_ring_constructor import PolynomialRing
 from sage.schemes.generic.homset import SchemeHomset_points
-from sage.schemes.generic.morphism import is_SchemeMorphism
-from .jacobian_morphism import JacobianMorphism_divisor_class_field
+from sage.schemes.hyperelliptic_curves.jacobian_morphism import JacobianMorphism_divisor_class_field
+
+lazy_import('sage.schemes.generic.morphism', 'SchemeMorphism')
 
 
 class JacobianHomset_divisor_classes(SchemeHomset_points):
@@ -139,12 +140,12 @@
                     return JacobianMorphism_divisor_class_field(self, (P1, P2))
                 if isinstance(P1, Polynomial) and isinstance(P2, Polynomial):
                     return JacobianMorphism_divisor_class_field(self, tuple(P))
-                if is_SchemeMorphism(P1) and is_SchemeMorphism(P2):
+                if isinstance(P1, SchemeMorphism) and isinstance(P2, SchemeMorphism):
                     return self(P1) - self(P2)
             raise TypeError("argument P (= %s) must have length 2" % P)
         elif isinstance(P, JacobianMorphism_divisor_class_field) and self == P.parent():
             return P
-        elif is_SchemeMorphism(P):
+        elif isinstance(P, SchemeMorphism):
             x0 = P[0]
             y0 = P[1]
             R, x = PolynomialRing(self.value_ring(), 'x').objgen()

src/sage/schemes/projective/projective_point.py

@@ -41,14 +41,12 @@
 from sage.rings.rational_field import QQ
 from sage.rings.ring import CommutativeRing
 from sage.schemes.generic.morphism import (SchemeMorphism,
-                                           is_SchemeMorphism,
                                            SchemeMorphism_point)
 from sage.structure.element import AdditiveGroupElement
 from sage.structure.richcmp import richcmp, op_EQ, op_NE
 from sage.structure.sequence import Sequence
 
 lazy_import('sage.rings.qqbar', 'number_field_elements_from_algebraics')
-lazy_import('sage.schemes.elliptic_curves.ell_point', 'EllipticCurvePoint_field')
 
 _NumberFields = NumberFields()
 
@@ -165,7 +163,7 @@ def __init__(self, X, v, check=True):
 
         if check:
             d = X.codomain().ambient_space().ngens()
-            if is_SchemeMorphism(v) or isinstance(v, EllipticCurvePoint_field):
+            if isinstance(v, SchemeMorphism):
                 v = list(v)
             else:
                 try:
@@ -1131,7 +1129,7 @@ def __init__(self, X, v, check=True):
 
         if check:
             d = X.codomain().ambient_space().ngens()
-            if is_SchemeMorphism(v) or isinstance(v, EllipticCurvePoint_field):
+            if isinstance(v, SchemeMorphism):
                 v = list(v)
             else:
                 try:

src/sage/schemes/toric/morphism.py

@@ -362,9 +362,7 @@
 # the toric varieties level from Morphism. See
 # https://groups.google.com/d/msg/sage-devel/qF4yU6Vdmao/wQlNrneSmWAJ
 from sage.categories.morphism import Morphism
-
 from sage.structure.richcmp import richcmp_not_equal, richcmp
-
 from sage.structure.sequence import Sequence
 from sage.rings.integer_ring import ZZ
 from sage.arith.misc import GCD as gcd
@@ -376,7 +374,6 @@
 
 from sage.schemes.generic.scheme import Scheme
 from sage.schemes.generic.morphism import (
-    is_SchemeMorphism,
     SchemeMorphism, SchemeMorphism_point, SchemeMorphism_polynomial
 )
 
@@ -431,7 +428,7 @@ def __init__(self, X, coordinates, check=True):
         if check:
             # Verify that there are the right number of coords
             # Why is it not done in the parent?
-            if is_SchemeMorphism(coordinates):
+            if isinstance(coordinates, SchemeMorphism):
                 coordinates = list(coordinates)
             if not isinstance(coordinates, (list, tuple)):
                 raise TypeError("coordinates must be a scheme point, list, "