gh-38323: some fixes for ruff code C41 (about loops and iteration)

    
a few minor code fixes in various places, about a better use of loops

https://docs.astral.sh/ruff/rules/#flake8-comprehensions-c4

### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
    
URL: #38323
Reported by: Frédéric Chapoton
Reviewer(s): Frédéric Chapoton, Matthias Köppe

src/sage/combinat/specht_module.py

@@ -920,9 +920,9 @@ def intrinsic_arrangement(self, base_ring=None):
         G = self._semigroup
 
         def t(i, j):
-            ret = [i for i in range(1, SGA.n+1)]
-            ret[i-1] = j
-            ret[j-1] = i
+            ret = list(range(1, SGA.n + 1))
+            ret[i - 1] = j
+            ret[j - 1] = i
             return SGA(G(ret))
 
         # Construct the hyperplanes

src/sage/env.py

@@ -429,9 +429,9 @@ def cython_aliases(required_modules=None, optional_modules=None):
                 else:
                     continue
             aliases["ECL_CFLAGS"] = list(filter(lambda s: not s.startswith('-I'), ecl_cflags))
-            aliases["ECL_INCDIR"] = list(map(lambda s: s[2:], filter(lambda s: s.startswith('-I'), ecl_cflags)))
-            aliases["ECL_LIBDIR"] = list(map(lambda s: s[2:], filter(lambda s: s.startswith('-L'), ecl_libs)))
-            aliases["ECL_LIBRARIES"] = list(map(lambda s: s[2:], filter(lambda s: s.startswith('-l'), ecl_libs)))
+            aliases["ECL_INCDIR"] = [s[2:] for s in filter(lambda s: s.startswith('-I'), ecl_cflags)]
+            aliases["ECL_LIBDIR"] = [s[2:] for s in filter(lambda s: s.startswith('-L'), ecl_libs)]
+            aliases["ECL_LIBRARIES"] = [s[2:] for s in filter(lambda s: s.startswith('-l'), ecl_libs)]
             aliases["ECL_LIBEXTRA"] = list(filter(lambda s: not s.startswith(('-l', '-L')), ecl_libs))
             continue
         else:

src/sage/geometry/hyperplane_arrangement/arrangement.py

@@ -1808,7 +1808,7 @@ def face_vector(self):
         return v
 
     @cached_method
-    def _parallel_hyperplanes(self):
+    def _parallel_hyperplanes(self) -> tuple:
         """
         Return the hyperplanes grouped into parallel sets.
 
@@ -1845,18 +1845,17 @@ def _parallel_hyperplanes(self):
              (Hyperplane t0 + 0*t1 - t2 + 0, (1, 0, -1), 0)))
         """
         V = self.parent().ambient_space()
-        parallels = dict()
+        parallels = {}
         for hyperplane in self:
             through_origin = V([list(hyperplane.A()), 0]).primitive(signed=False)
             parallel_planes = parallels.get(through_origin, [])
             A = through_origin.A()
             b = hyperplane.b() * (A / hyperplane.A())
             parallel_planes.append([b, (hyperplane, A, b)])
             parallels[through_origin] = parallel_planes
-        parallels = [tuple(tuple(hyperplane[1]
-                           for hyperplane in sorted(parallels[key])))
-                     for key in parallels.keys()]
-        return tuple(sorted(parallels))
+        parallels = sorted(tuple(hyperplane[1] for hyperplane in sorted(value))
+                           for key, value in parallels.items())
+        return tuple(parallels)
 
     def vertices(self, exclude_sandwiched=False):
         """

src/sage/graphs/generators/smallgraphs.py

@@ -2951,7 +2951,7 @@ def GritsenkoGraph():
              (33, 49), (33, 51), (33, 57), (33, 61)]
     # use the union of the orbits of a on the edges
     return Graph(reduce(lambda x, y: x + y,
-                        map(lambda o: a.orbit(o, action='OnSets'), edges)),
+                        (a.orbit(o, action='OnSets') for o in edges)),
                  format='list_of_edges',
                  name="Gritsenko strongly regular graph")
 
@@ -4734,7 +4734,7 @@ def _EllipticLinesProjectivePlaneScheme(k):
     gp = libgap.Action(g, libgap.Orbit(g, l, libgap.OnLines), libgap.OnLines)
     orbitals = gp.Orbits(list(product(gp.Orbit(1), gp.Orbit(1))),
                          libgap.OnTuples)
-    mats = map(lambda o: [(int(x[0]) - 1, int(x[1]) - 1) for x in o], orbitals)
+    mats = ([(int(x[0]) - 1, int(x[1]) - 1) for x in o] for o in orbitals)
     return [matrix((q * (q - 1)) // 2, lambda i, j: 1 if (i, j) in x else 0)
             for x in mats]
 
@@ -4934,7 +4934,7 @@ def JankoKharaghaniTonchevGraph():
             301, 304, 308, 309, 310, 312, 313, 314, 316, 317, 318)
     Gamma = Graph(multiedges=False, name='Janko-Kharaghani-Tonchev')
     for i, b in ((1, B1), (163, B163)):
-        for j in map(lambda x: x[0], st.OrbitsDomain(b)):
+        for j in (x[0] for x in st.OrbitsDomain(b)):
             Gamma.add_edges(map(tuple, G.Orbit(libgap.Set([i, j]), libgap.OnSets)))
     Gamma.relabel(range(Gamma.order()))
     return Gamma

src/sage/graphs/schnyder.py

@@ -509,7 +509,7 @@ def _compute_coordinates(g, x):
     for v in g.vertices(sort=False):
         if v not in [t1.label, t2.label, t3.label]:
             # Computing coordinates for v
-            r = list((0, 0, 0))
+            r = [0, 0, 0]
 
             for i in [0, 1, 2]:
                 # Computing size of region i:

src/sage/knots/link.py

@@ -4033,7 +4033,7 @@ def _knotinfo_matching_list(self):
             Sn = KnotInfoSeries(cr, is_knot, False)
             la = Sa.lower_list(oriented=True, comp=co, det=det, homfly=Hp)
             ln = Sn.lower_list(oriented=True, comp=co, det=det, homfly=Hp)
-            l = sorted(list(set(la + ln)))
+            l = sorted(set(la + ln))
 
         br = self.braid()
         br_ind = br.strands()
@@ -4452,7 +4452,7 @@ def answer_list(l):
 
             if not l[0].is_knot():
                 S = l[0].series(oriented=True)
-                if set(list(S)) == set(l):
+                if set(S) == set(l):
                     return answer_unori(S)
 
             raise NotImplementedError('this link cannot be uniquely determined%s' % non_unique_hint)

src/sage/matroids/matroids_plot_helpers.py

@@ -168,11 +168,13 @@ def it(M, B1, nB1, lps):
             # loop over L1,L2,L3
             cc = interval*j
             pts[i[j-1]] = (cc*pt1[0]+(1-cc)*pt2[0], cc*pt1[1]+(1-cc)*pt2[1])
-    trilines = [list(set(x)) for x in lines if len(x) >= 3]
-    curvedlines = [list(set(list(x)).difference(set(lps)))
-                   for x in M.flats(2) if set(list(x)) not in trilines if
-                   len(list(x)) >= 3]
-    nontripts = [i for i in nB1 if i not in pts.keys()]
+    trilines = [set(x) for x in lines if len(x) >= 3]
+    set_lps = set(lps)
+    curvedlines = [list(sx.difference(set_lps))
+                   for x in M.flats(2) if (sx := set(x)) not in trilines
+                   and len(list(x)) >= 3]
+    nontripts = [i for i in nB1 if i not in pts]
+    trilines = [list(s) for s in trilines]
     return pts, trilines, nontripts, curvedlines
 
 
@@ -206,12 +208,12 @@ def trigrid(tripts):
             This method does NOT do any checks.
     """
     pairs = [[0, 1], [1, 2], [0, 2]]
-    cpt = list((float(tripts[0][0]+tripts[1][0]+tripts[2][0])/3,
-               float(tripts[0][1]+tripts[1][1]+tripts[2][1])/3))
+    cpt = [float(tripts[0][0] + tripts[1][0] + tripts[2][0]) / 3,
+           float(tripts[0][1] + tripts[1][1] + tripts[2][1]) / 3]
     grid = [cpt]
-    for p in pairs:
-        pt = list((float(tripts[p[0]][0]+tripts[p[1]][0]+cpt[0])/3,
-                  float(tripts[p[0]][1]+tripts[p[1]][1]+cpt[1])/3))
+    for p, q in pairs:
+        pt = [float(tripts[p][0] + tripts[q][0] + cpt[0]) / 3,
+              float(tripts[p][1] + tripts[q][1] + cpt[1]) / 3]
         grid.append(pt)
     return grid
 
@@ -852,9 +854,8 @@ def geomrep(M1, B1=None, lineorders1=None, pd=None, sp=False):
             trilines.extend(curvedlines)
         else:
             pts2 = M._cached_info['plot_positions']
-            trilines = [list(set(list(x)).difference(L | P))
-                        for x in M1.flats(2)
-                        if len(list(x)) >= 3]
+            trilines = [list(set(x).difference(L | P))
+                        for x in M1.flats(2) if len(list(x)) >= 3]
         pl = [list(x) for x in pts2.values()]
         lims = tracklims([None, None, None, None], [pt[0] for pt in pl],
                          [pt[1] for pt in pl])

src/sage/rings/lazy_series.py

@@ -476,7 +476,7 @@ def coefficients(self, n=None):
                 return lazy_list(coeffs)
 
             # flatten out the generator in the multivariate case
-            return lazy_list(chain.from_iterable(map(lambda coeff: coeff.coefficients(), coeffs)))
+            return lazy_list(chain.from_iterable((coeff.coefficients() for coeff in coeffs)))
 
         if isinstance(self, LazyPowerSeries) and self.parent()._arity == 1:
             from sage.misc.superseded import deprecation
@@ -486,7 +486,7 @@ def coefficients(self, n=None):
             return list(islice(coeffs, n))
 
         # flatten out the generator in the multivariate case
-        return list(islice(chain.from_iterable(map(lambda coeff: coeff.coefficients(), coeffs)), n))
+        return list(islice(chain.from_iterable((coeff.coefficients() for coeff in coeffs)), n))
 
     def map_coefficients(self, f):
         r"""

src/sage/rings/number_field/galois_group.py

@@ -573,9 +573,8 @@ def _elts(self):
         """
         if self._gc_numbering:
             # PARI computes all the elements of self anyway, so we might as well store them
-            return sorted([self(x, check=False) for x in self._pari_data[5]])
-        else:
-            return sorted(list(self.iteration()))
+            return sorted(self(x, check=False) for x in self._pari_data[5])
+        return sorted(self.iteration())
 
     @lazy_attribute
     def _gens(self):

src/sage/rings/valuation/augmented_valuation.py

@@ -1508,7 +1508,7 @@ def lift_to_key(self, F, check=True):
             coefficients[-2] %= self.phi()
         tau = self.value_group().index(self._base_valuation.value_group())
         vf = self._mu * tau * F.degree()
-        ret = self.domain().change_ring(self.domain())([c for c in coefficients])(self.phi()**tau)
+        ret = self.domain().change_ring(self.domain())(coefficients)(self.phi()**tau)
         ret = self.simplify(ret, error=vf, force=True)
         ret = ret.map_coefficients(_lift_to_maximal_precision)
         assert (ret == self.phi()) == (F == F.parent().gen())

src/sage/tensor/modules/comp.py

@@ -1599,7 +1599,7 @@ def __add__(self, other):
         if nproc != 1:
             # Parallel computation
             lol = lambda lst, sz: [lst[i:i+sz] for i in range(0, len(lst), sz)]
-            ind_list = [ind for ind in other._comp]
+            ind_list = list(other._comp)
             ind_step = max(1, int(len(ind_list)/nproc/2))
             local_list = lol(ind_list, ind_step)
             # list of input parameters
@@ -1822,7 +1822,7 @@ def __mul__(self, other):
                 if nproc != 1:
                     # Parallel computation
                     lol = lambda lst, sz: [lst[i:i+sz] for i in range(0, len(lst), sz)]
-                    ind_list = [ind for ind in result.non_redundant_index_generator()]
+                    ind_list = list(result.non_redundant_index_generator())
                     ind_step = max(1, int(len(ind_list)/nproc))
                     local_list = lol(ind_list, ind_step)
                     # list of input parameters:
@@ -2344,7 +2344,7 @@ def compprod(a, b):
             # parallel computation
             nproc = Parallelism().get('tensor')
             lol = lambda lst, sz: [lst[i:i+sz] for i in range(0, len(lst), sz)]
-            ind_list = [ind for ind in res.non_redundant_index_generator()]
+            ind_list = list(res.non_redundant_index_generator())
             ind_step = max(1, int(len(ind_list)/nproc/2))
             local_list = lol(ind_list, ind_step)
 
@@ -3526,7 +3526,7 @@ def __add__(self, other):
                     # Parallel computation
                     lol = lambda lst, sz: [lst[i:i+sz] for i in
                                            range(0, len(lst), sz)]
-                    ind_list = [ind for ind in other._comp]
+                    ind_list = list(other._comp)
                     ind_step = max(1, int(len(ind_list)/nproc/2))
                     local_list = lol(ind_list, ind_step)
                     # list of input parameters
@@ -3580,7 +3580,7 @@ def paral_sum(a, b, local_list_ind):
         if nproc != 1:
             # Parallel computation
             lol = lambda lst, sz: [lst[i:i+sz] for i in range(0, len(lst), sz)]
-            ind_list = [ind for ind in result.non_redundant_index_generator()]
+            ind_list = list(result.non_redundant_index_generator())
             ind_step = max(1, int(len(ind_list)/nproc/2))
             local_list = lol(ind_list, ind_step)
             # definition of the list of input parameters
@@ -3683,7 +3683,7 @@ def __mul__(self, other):
         if nproc != 1:
             # Parallel computation
             lol = lambda lst, sz: [lst[i:i+sz] for i in range(0, len(lst), sz)]
-            ind_list = [ind for ind in self._comp]
+            ind_list = list(self._comp)
             ind_step = max(1, int(len(ind_list)/nproc))
             local_list = lol(ind_list, ind_step)
             # list of input parameters:
@@ -4003,7 +4003,7 @@ def non_redundant_index_generator(self):
                         if ind[isym[k-1]] == imax:
                             return
                         ind[pos] = ind[isym[k-1]] + 1
-            if not any([pos in isym for isym in sym]) and not any([pos in isym for isym in antisym]):
+            if not any(pos in isym for isym in sym) and not any(pos in isym for isym in antisym):
                 sym.append([pos]) # treat non-symmetrized indices as being symmetrized with themselves
         while True:
             yield tuple(ind)
@@ -5038,7 +5038,7 @@ def __add__(self, other):
                 # parallel sum
                 lol = lambda lst, sz: [lst[i:i+sz] for i
                                        in range(0, len(lst), sz)]
-                ind_list = [ind for ind in other._comp]
+                ind_list = list(other._comp)
                 ind_step = max(1, int(len(ind_list)/nproc/2))
                 local_list = lol(ind_list, ind_step)
                 # definition of the list of input parameters
@@ -5329,7 +5329,7 @@ def __add__(self, other):
             if nproc != 1:
                 # Parallel computation
                 lol = lambda lst, sz: [lst[i:i+sz] for i in range(0, len(lst), sz)]
-                ind_list = [ind for ind in other._comp]
+                ind_list = list(other._comp)
                 ind_step = max(1, int(len(ind_list)/nproc/2))
                 local_list = lol(ind_list, ind_step)
                 # list of input parameters

src/sage/tensor/modules/free_module_tensor.py

@@ -1108,7 +1108,7 @@ class :class:`~sage.tensor.modules.comp.Components`
             if nproc != 1:
                 # Parallel computation
                 lol = lambda lst, sz: [lst[i:i+sz] for i in range(0, len(lst), sz)]
-                ind_list = [ind for ind in new_comp.non_redundant_index_generator()]
+                ind_list = list(new_comp.non_redundant_index_generator())
                 ind_step = max(1, int(len(ind_list)/nproc/2))
                 local_list = lol(ind_list, ind_step)
                 # list of input parameters