Make matroid copy and deepcopy simply return self

src/sage/matroids/advanced.py

@@ -52,6 +52,7 @@
 from .minor_matroid import MinorMatroid
 from .dual_matroid import DualMatroid
 from .rank_matroid import RankMatroid
+from .circuits_matroid import CircuitsMatroid
 from .circuit_closures_matroid import CircuitClosuresMatroid
 from .basis_matroid import BasisMatroid
 from .linear_matroid import LinearMatroid, RegularMatroid, BinaryMatroid, TernaryMatroid, QuaternaryMatroid

src/sage/matroids/basis_matroid.pyx

@@ -1161,46 +1161,6 @@ cdef class BasisMatroid(BasisExchangeMatroid):
         else:
             return rich_to_bool(op, 1)
 
-    def __copy__(self):
-        """
-        Create a shallow copy.
-
-        EXAMPLES::
-
-            sage: from sage.matroids.advanced import *
-            sage: M = BasisMatroid(matroids.catalog.Vamos())
-            sage: N = copy(M)  # indirect doctest
-            sage: M == N
-            True
-        """
-        N = BasisMatroid(M=self)
-        N.rename(self.get_custom_name())
-        return N
-
-    def __deepcopy__(self, memo=None):
-        """
-        Create a deep copy.
-
-        .. NOTE::
-
-            Identical to shallow copy for BasisMatroid class.
-
-        EXAMPLES::
-
-            sage: from sage.matroids.advanced import *
-            sage: M = BasisMatroid(matroids.catalog.Vamos())
-            sage: N = deepcopy(M)  # indirect doctest
-            sage: M == N
-            True
-            sage: M.groundset() is N.groundset()
-            False
-        """
-        if memo is None:
-            memo = {}
-        N = BasisMatroid(M=self)
-        N.rename(self.get_custom_name())
-        return N
-
     def __reduce__(self):
         """
         Save the matroid for later reloading.

src/sage/matroids/circuit_closures_matroid.pyx

@@ -46,15 +46,6 @@ Note that the class does not implement custom minor and dual operations::
 AUTHORS:
 
 - Rudi Pendavingh, Stefan van Zwam (2013-04-01): initial version
-
-TESTS::
-
-    sage: from sage.matroids.advanced import *
-    sage: M = CircuitClosuresMatroid(matroids.catalog.Fano())
-    sage: TestSuite(M).run()
-
-Methods
-=======
 """
 # ****************************************************************************
 #       Copyright (C) 2013 Rudi Pendavingh <[email protected]>
@@ -131,7 +122,8 @@ cdef class CircuitClosuresMatroid(Matroid):
         True
     """
 
-    # NECESSARY
+    # necessary
+
     def __init__(self, M=None, groundset=None, circuit_closures=None):
         """
         Initialization of the matroid. See class docstring for full
@@ -154,6 +146,12 @@ cdef class CircuitClosuresMatroid(Matroid):
             ....:                          4: ['abcdefgh']})
             sage: M.equals(matroids.catalog.P8())
             True
+
+        TESTS::
+
+            sage: from sage.matroids.advanced import *
+            sage: M = CircuitClosuresMatroid(matroids.catalog.Fano())
+            sage: TestSuite(M).run()
         """
         if M is not None:
             self._groundset = M.groundset()
@@ -206,7 +204,8 @@ cdef class CircuitClosuresMatroid(Matroid):
         """
         return len(self._max_independent(X))
 
-    # OPTIONAL, OPTIMIZED FOR THIS CLASS
+    # optional
+
     cpdef full_rank(self) noexcept:
         r"""
         Return the rank of the matroid.
@@ -413,7 +412,8 @@ cdef class CircuitClosuresMatroid(Matroid):
                 SN.append(C)
         return SM._isomorphism(SN) is not None
 
-    # REPRESENTATION
+    # representation
+
     def _repr_(self):
         """
         Return a string representation of the matroid.
@@ -430,7 +430,7 @@ cdef class CircuitClosuresMatroid(Matroid):
         """
         return Matroid._repr_(self) + " with circuit-closures\n" + setprint_s(self._circuit_closures)
 
-    # COMPARISON
+    # comparison
 
     def __hash__(self):
         r"""
@@ -490,52 +490,7 @@ cdef class CircuitClosuresMatroid(Matroid):
             return rich_to_bool(op, 1)
         return richcmp(lt._circuit_closures, rt._circuit_closures, op)
 
-    # COPYING, LOADING, SAVING
-
-    def __copy__(self):
-        """
-        Create a shallow copy.
-
-        EXAMPLES::
-
-            sage: M = matroids.catalog.Vamos()
-            sage: N = copy(M)  # indirect doctest
-            sage: M == N
-            True
-            sage: M.groundset() is N.groundset()
-            True
-        """
-        N = CircuitClosuresMatroid(groundset=[], circuit_closures={})
-        N._groundset = self._groundset
-        N._circuit_closures = self._circuit_closures
-        N._matroid_rank = self._matroid_rank
-        N.rename(self.get_custom_name())
-        return N
-
-    def __deepcopy__(self, memo=None):
-        """
-        Create a deep copy.
-
-        .. NOTE::
-
-            Since matroids are immutable, a shallow copy normally suffices.
-
-        EXAMPLES::
-
-            sage: M = matroids.catalog.Vamos()
-            sage: N = deepcopy(M)  # indirect doctest
-            sage: M == N
-            True
-            sage: M.groundset() is N.groundset()
-            False
-        """
-        if memo is None:
-            memo = {}
-        from copy import deepcopy
-        # Since matroids are immutable, N cannot reference itself in correct code, so no need to worry about the recursion.
-        N = CircuitClosuresMatroid(groundset=deepcopy(self._groundset, memo), circuit_closures=deepcopy(self._circuit_closures, memo))
-        N.rename(deepcopy(self.get_custom_name(), memo))
-        return N
+    # copying, loading, saving
 
     def __reduce__(self):
         """

src/sage/matroids/circuits_matroid.pyx

@@ -337,55 +337,6 @@ cdef class CircuitsMatroid(Matroid):
 
     # copying, loading, saving
 
-    def __copy__(self):
-        """
-        Create a shallow copy.
-
-        EXAMPLES::
-
-            sage: from sage.matroids.circuits_matroid import CircuitsMatroid
-            sage: M = CircuitsMatroid(matroids.catalog.Vamos())
-            sage: N = copy(M)  # indirect doctest
-            sage: M == N
-            True
-            sage: M.groundset() is N.groundset()
-            True
-        """
-        N = CircuitsMatroid(groundset=[], circuits=[])
-        N._groundset = self._groundset
-        N._C = self._C
-        N._k_C = self._k_C
-        N._nsc_defined = self._nsc_defined
-        N._matroid_rank = self._matroid_rank
-        N.rename(self.get_custom_name())
-        return N
-
-    def __deepcopy__(self, memo=None):
-        """
-        Create a deep copy.
-
-        .. NOTE::
-
-            Since matroids are immutable, a shallow copy normally suffices.
-
-        EXAMPLES::
-
-            sage: from sage.matroids.circuits_matroid import CircuitsMatroid
-            sage: M = CircuitsMatroid(matroids.catalog.Vamos())
-            sage: N = deepcopy(M)  # indirect doctest
-            sage: M == N
-            True
-            sage: M.groundset() is N.groundset()
-            False
-        """
-        if memo is None:
-            memo = {}
-        from copy import deepcopy
-        # Since matroids are immutable, N cannot reference itself in correct code, so no need to worry about the recursion.
-        N = CircuitsMatroid(groundset=deepcopy(self._groundset, memo), circuits=deepcopy(frozenset(self._C), memo))
-        N.rename(deepcopy(self.get_custom_name(), memo))
-        return N
-
     def __reduce__(self):
         """
         Save the matroid for later reloading.

src/sage/matroids/dual_matroid.py

@@ -386,7 +386,8 @@ def dual(self):
         """
         return self._matroid
 
-    # REPRESENTATION
+    # representation
+
     def _repr_(self):
         """
         Return a string representation of the matroid.
@@ -404,7 +405,7 @@ def _repr_(self):
         """
         return "Dual of '" + repr(self._matroid) + "'"
 
-    # COMPARISON
+    # comparison
 
     def __hash__(self):
         r"""
@@ -494,46 +495,7 @@ def __ne__(self, other):
         """
         return not self == other
 
-    # COPYING, LOADING, SAVING
-
-    def __copy__(self):
-        """
-        Create a shallow copy.
-
-        EXAMPLES::
-
-            sage: M = matroids.catalog.Vamos()
-            sage: N = copy(M)  # indirect doctest
-            sage: M == N
-            True
-            sage: M.groundset() is N.groundset()
-            True
-        """
-        N = DualMatroid(self._matroid)
-        N.rename(self.get_custom_name())
-        return N
-
-    def __deepcopy__(self, memo={}):
-        """
-        Create a deep copy.
-
-        .. NOTE::
-
-            Since matroids are immutable, a shallow copy normally suffices.
-
-        EXAMPLES::
-
-            sage: M = matroids.catalog.Vamos().dual()
-            sage: N = deepcopy(M)  # indirect doctest
-            sage: M == N
-            True
-            sage: M.groundset() is N.groundset()
-            False
-        """
-        from copy import deepcopy
-        N = DualMatroid(deepcopy(self._matroid, memo))
-        N.rename(deepcopy(self.get_custom_name(), memo))
-        return N
+    # copying, loading, saving
 
     def __reduce__(self):
         """

src/sage/matroids/graphic_matroid.py

@@ -450,46 +450,6 @@ def __ne__(self, other):
 
     # Copying, loading, saving:
 
-    def __copy__(self):
-        """
-        Create a shallow copy.
-
-        Creating a ``GraphicMatroid`` instance will build a new graph, so
-        the copies have no attributes in common.
-
-        EXAMPLES::
-
-            sage: M = Matroid(graphs.PappusGraph())
-            sage: N = copy(M)
-            sage: M == N
-            True
-            sage: M._G is N._G
-            False
-        """
-        N = GraphicMatroid(self._G)
-        N.rename(self.get_custom_name())
-        return N
-
-    def __deepcopy__(self, memo={}):
-        """
-        Create a deep copy.
-
-        .. NOTE::
-
-            Since matroids are immutable, a shallow copy normally suffices.
-
-        EXAMPLES::
-
-            sage: M = Matroid(graphs.PetersenGraph())
-            sage: N = deepcopy(M)
-            sage: N == M
-            True
-        """
-        # The only real difference between this and __copy__() is the memo
-        N = GraphicMatroid(deepcopy(self._G, memo))
-        N.rename(deepcopy(self.get_custom_name(), memo))
-        return N
-
     def __reduce__(self):
         """
         Save the matroid for later reloading.

src/sage/matroids/lean_matrix.pyx

@@ -476,32 +476,6 @@ cdef class LeanMatrix:
 
     #    Copying, loading, saving:
 
-    def __copy__(self):
-        """
-        Return a copy of ``self``.
-
-        EXAMPLES::
-
-            sage: from sage.matroids.lean_matrix import *
-            sage: A = GenericMatrix(2, 5, Matrix(GF(5), [[1, 0, 1, 1, 1], [0, 1, 1, 2, 3]]))
-            sage: A == copy(A)  # indirect doctest
-            True
-        """
-        return self.copy()
-
-    def __deepcopy__(self, memo=None):
-        """
-        Return a deep copy of ``self``.
-
-        EXAMPLES::
-
-            sage: from sage.matroids.lean_matrix import *
-            sage: A = GenericMatrix(2, 5, Matrix(GF(5), [[1, 0, 1, 1, 1], [0, 1, 1, 2, 3]]))
-            sage: A == deepcopy(A)  # indirect doctest
-            True
-        """
-        return self.copy()
-
     def __reduce__(self):
         """
         Save the object.