micro details in pyx files in matroids

src/sage/matroids/graphic_matroid.pyx

@@ -650,7 +650,7 @@ cdef class GraphicMatroid(Matroid):
         DS_vertices = DisjointSet_of_hashables(all_vertices)
         for u, v, l in not_our_edges:
             DS_vertices.union(u, v)
-        return len(X) - (DS_vertices.number_of_subsets() - Integer(1))
+        return len(X) - (DS_vertices.number_of_subsets() - 1)
 
     cpdef bint _is_circuit(self, frozenset X) noexcept:
         """
@@ -1699,9 +1699,9 @@ cdef class GraphicMatroid(Matroid):
         # If a vertex has degree 1, or 2, or 3, we already handled it.
         for u in vertices:
             if G.degree(u) > 3:
-                elts_incident = [l for (_, _, l) in G.edges_incident(u)]
+                elts_incident = [l for _, _, l in G.edges_incident(u)]
                 x = elts_incident.pop()
-                for i in range(1, (len(elts_incident) - Integer(1))):
+                for i in range(1, len(elts_incident) - 1):
                     groups = combinations(elts_incident, i)
                     for g in groups:
                         g = list(g)

src/sage/matroids/lean_matrix.pyx

@@ -208,9 +208,9 @@ cdef class LeanMatrix:
             sage: A.base_ring()
             Traceback (most recent call last):
             ...
-            NotImplementedError: subclasses need to implement this.
+            NotImplementedError: subclasses need to implement this
         """
-        raise NotImplementedError("subclasses need to implement this.")
+        raise NotImplementedError("subclasses need to implement this")
 
     cpdef characteristic(self):
         """
@@ -357,7 +357,7 @@ cdef class LeanMatrix:
         and compatible dimensions.
         """
         cdef LeanMatrix A = type(self)(self.nrows(), other.ncols())
-        cdef i, j, k
+        cdef long i, j, k
         for i in range(self.nrows()):
             for j in range(other.ncols()):
                 for k in range(self.ncols()):
@@ -487,9 +487,9 @@ cdef class LeanMatrix:
             sage: A == loads(dumps(A))  # indirect doctest
             Traceback (most recent call last):
             ...
-            NotImplementedError: subclasses need to implement this.
+            NotImplementedError: subclasses need to implement this
         """
-        raise NotImplementedError("subclasses need to implement this.")
+        raise NotImplementedError("subclasses need to implement this")
 
     cdef shifting_all(self, P_rows, P_cols, Q_rows, Q_cols, int m):
         r"""

src/sage/matroids/linear_matroid.pyx

@@ -878,8 +878,8 @@ cdef class LinearMatroid(BasisExchangeMatroid):
         try:
             if GF2_not_defined:
                 GF2 = GF(2)
-                GF2_zero = GF2(0)
-                GF2_one = GF2(1)
+                GF2_zero = GF2.zero()
+                GF2_one = GF2.one()
                 GF2_not_defined = False
         except ImportError:
             pass
@@ -3099,8 +3099,8 @@ cdef class BinaryMatroid(LinearMatroid):
         global GF2, GF2_zero, GF2_one, GF2_not_defined
         if GF2_not_defined:
             GF2 = GF(2)
-            GF2_zero = GF2(0)
-            GF2_one = GF2(1)
+            GF2_zero = GF2.zero()
+            GF2_one = GF2.one()
             GF2_not_defined = False
 
         # Setup representation; construct displayed basis

src/sage/matroids/matroid.pyx

@@ -7933,8 +7933,8 @@ cdef class Matroid(SageObject):
         a = x
         b = y
         R = ZZ['x, y']
-        x, y = R._first_ngens(2)
-        T = R(0)
+        x, y = R.gens()
+        T = R.zero()
         for B in self.bases_iterator():
             T += x ** len(self._internal(B)) * y ** len(self._external(B))
         if a is not None and b is not None: