sagemathgh-40960: trying to get rid of some .iteritems
    
as this is just an old syntax from python2, long gone

### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
    
URL: sagemath#40960
Reported by: Frédéric Chapoton
Reviewer(s): Martin Rubey

Author: Release Manager

src/sage/algebras/exterior_algebra_groebner.pyx

@@ -280,7 +280,7 @@ cdef class GroebnerStrategy:
                    sparse=True)
         M.echelonize()  # Do this in place
         lead_supports = set((<GBElement> f).lsi for f in L)
-        return [GBElement(self.E.element_class(self.E, {self.int_to_bitset(r - Integer(j)): c for j, c in M[i].iteritems()}),
+        return [GBElement(self.E.element_class(self.E, {self.int_to_bitset(r - Integer(j)): c for j, c in M[i].items()}),
                           self.int_to_bitset(Integer(r - p)),
                           Integer(r - p))
                 for i, p in enumerate(M.pivots())

src/sage/algebras/hecke_algebras/cubic_hecke_algebra.py

@@ -578,7 +578,7 @@ def formal_markov_trace(self, extended=False, field_embedding=False):
             mtcf = [M.from_vector(cf.to_vector()) for cf in mtcf]
 
         R = M.base_ring()
-        return M.linear_combination((mtcf[i], R(val)) for i, val in vs.iteritems())
+        return M.linear_combination((mtcf[i], R(val)) for i, val in vs.items())
 
 
 class CubicHeckeAlgebra(CombinatorialFreeModule):

src/sage/algebras/letterplace/free_algebra_letterplace.pyx

@@ -817,7 +817,7 @@ cdef class FreeAlgebra_letterplace(Parent):
         cdef dict out = {}
         self.set_degbound(l // self._ngens)
         cdef Py_ssize_t n = self._current_ring.ngens()
-        for e, c in D.iteritems():
+        for e, c in D.items():
             out[tuple(e) + (0,) * (n - l)] = c
         return FreeAlgebraElement_letterplace(self, self._current_ring(out),
                                               check=check)

src/sage/algebras/lie_algebras/bgg_dual_module.py

@@ -746,10 +746,10 @@ def _construct_next_level(self):
                 mat = matrix(R, [[b[s] for s in supp] for b in wt_basis])
                 mat.echelonize()
                 for i, k in enumerate(self._weight_space_bases[mu]):
-                    data = {supp[ind]: R(c) for ind, c in mat[i].iteritems() if c}
+                    data = {supp[ind]: R(c) for ind, c in mat[i].items() if c}
                     self._basis[k] = ambient.element_class(ambient, data)
                 i = mat.nrows() - 1
-                data = {supp[ind]: R(c) for ind, c in mat[i].iteritems() if c}
+                data = {supp[ind]: R(c) for ind, c in mat[i].items() if c}
                 if data:
                     next_level[key] = ambient.element_class(ambient, data)
                     self._basis[key] = next_level[key]

src/sage/algebras/lie_algebras/center_uea.py

@@ -309,7 +309,7 @@ def _construct_next_degree(self):
                 continue
             M = matrix(R, [[v[s] for v in ad] for s in supp])
             ker = M.right_kernel_matrix()
-            vecs = [self._reduce(UEA.linear_combination((vecs[i], c) for i, c in kv.iteritems()))
+            vecs = [self._reduce(UEA.linear_combination((vecs[i], c) for i, c in kv.items()))
                     for kv in ker.rows()]
 
         # Lastly, update the appropriate data

src/sage/algebras/lie_algebras/verma_module.py

@@ -1490,7 +1490,8 @@ def singular_vector(self):
                             continue
                         M = matrix(pbw.base_ring(), [[v[s] for v in image] for s in supp])
                         ker = M.right_kernel_matrix()
-                        basis = [C.linear_combination((basis[j], c) for j, c in kv.iteritems())
+                        basis = [C.linear_combination((basis[j], c)
+                                                      for j, c in kv.items())
                                  for kv in ker.rows()]
 
                     assert len(basis) == 1

src/sage/categories/finite_dimensional_lie_algebras_with_basis.py

@@ -1788,7 +1788,7 @@ def compute_diff(k):
                                 vec = elt.to_vector()
                             else:
                                 vec = Lmod.coordinate_vector(elt.to_vector())
-                            for key, coeff in vec.iteritems():
+                            for key, coeff in vec.items():
                                 if not coeff:
                                     continue
                                 s, A = sgn(key, Z)

src/sage/groups/perm_gps/permgroup_element.pyx

@@ -1,4 +1,4 @@
-r"""
+"""
 Permutation group elements
 
 AUTHORS:
@@ -1599,7 +1599,7 @@ cdef class PermutationGroupElement(MultiplicativeGroupElement):
         from_gap = self._parent._domain_from_gap
         to_gap = self._parent._domain_to_gap
         cdef int i
-        return {e:from_gap[self.perm[i-1]+1] for e,i in to_gap.iteritems()}
+        return {e: from_gap[self.perm[i - 1] + 1] for e, i in to_gap.items()}
 
     def multiplicative_order(self):
         r"""

src/sage/matrix/args.pyx

@@ -1403,7 +1403,7 @@ cdef class MatrixArgs:
                                                            for vec in e])
             self.entries = []
             for i, row in enumerate(e):
-                for j, val in (<Vector?>row).iteritems():
+                for j, val in (<Vector?>row).items():
                     self.entries.append(make_SparseEntry(i, j, val))
 
             self.set_ncols(max((<Vector>vec)._parent.ambient_module().rank() for vec in e))

src/sage/matrix/matrix_generic_sparse.pyx

@@ -396,7 +396,7 @@ cdef class Matrix_generic_sparse(matrix_sparse.Matrix_sparse):
         cdef list v = self.fetch('list')
         if v is None:
             v = [self._zero]*(self._nrows * self._ncols)
-            for (i,j), x in self._entries.iteritems():
+            for (i,j), x in self._entries.items():
                 v[i*self._ncols + j] = x
             self.cache('list', v)
         return v
@@ -498,7 +498,7 @@ def Matrix_sparse_from_rows(X):
     R = X[0].base_ring()
     ncols = X[0].degree()
     for i from 0 <= i < len(X):
-        for j, x in X[i].iteritems():
-            entries[(i,j)] = x
+        for j, x in X[i].items():
+            entries[(i, j)] = x
     M = matrix_space.MatrixSpace(R, len(X), ncols, sparse=True)
     return M(entries, coerce=False, copy=False)