gh-40723: fix some ruff PERF in rings/
    
fix some suggestions of

`ruff check --select=PERF src/sage/rings/`

about list comprehensions

### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
    
URL: #40723
Reported by: Frédéric Chapoton
Reviewer(s): Martin Rubey

Author: Release Manager

src/sage/rings/function_field/drinfeld_modules/finite_drinfeld_module.py

@@ -633,10 +633,9 @@ def _frobenius_charpoly_gekeler(self):
         # The system is solved over K, but the coefficients should all
         # be in Fq We project back into Fq here.
         sol_Fq = [K(x).vector()[0] for x in sol]
-        char_poly = []
-        for i in range(r):
-            char_poly.append([sol_Fq[block_shifts[i] + j]
-                              for j in range(shifts[i])])
+        char_poly = [[sol_Fq[block_shifts[i] + j]
+                      for j in range(shifts[i])]
+                     for i in range(r)]
         return PolynomialRing(A, name='X')(char_poly + [1])
 
     def _frobenius_charpoly_motive(self):
@@ -651,8 +650,9 @@ def _frobenius_charpoly_motive(self):
         Instead, use :meth:`frobenius_charpoly` with the option
         `algorithm='motive'`.
 
-        OUTPUT: a univariate polynomial with coefficients in the
-                function ring
+        OUTPUT:
+
+        a univariate polynomial with coefficients in the function ring
 
         EXAMPLES::
 

src/sage/rings/function_field/ideal.py

@@ -273,11 +273,11 @@ def gens_reduced(self):
         gens = self.gens()
         if len(gens) == 1:
             return gens
-        candidate_gensets = []
-        for genset in powerset(gens):
-            if self.parent()(genset) == self:
-                candidate_gensets.append(genset)
-        candidate_gensets.sort(key=lambda item: (len(item), len(repr(item)), item))
+        candidate_gensets = [genset for genset in powerset(gens)
+                             if self.parent()(genset) == self]
+        candidate_gensets.sort(key=lambda item: (len(item),
+                                                 len(repr(item)),
+                                                 item))
         return candidate_gensets[0]
 
     def ring(self):

src/sage/rings/function_field/ideal_polymod.py

@@ -1251,9 +1251,8 @@ def _gens_two(self) -> tuple:
 
         R = hnf.base_ring()
 
-        basis = []
-        for row in hnf:
-            basis.append(sum([c1 * c2 for c1, c2 in zip(row, O.basis())]))
+        basis = [sum(c1 * c2 for c1, c2 in zip(row, O.basis()))
+                 for row in hnf]
 
         n = len(basis)
         alpha = None

src/sage/rings/function_field/jacobian_base.py

@@ -540,7 +540,7 @@ def order(self, algorithm='numeric'):
 
         return sum(bs)
 
-    def get_points(self, n):
+    def get_points(self, n) -> list:
         """
         Return `n` points of the Jacobian group.
 

src/sage/rings/function_field/place_polymod.py

@@ -510,13 +510,12 @@ def to_V(e):
             v = O._coordinate_vector(e)
             vec = []
             for i in reversed(range(n)):
-                q,r = v[i].quo_rem(M[i,i])
+                q, r = v[i].quo_rem(M[i, i])
                 v -= q * M[i]
-                for j in range(degs[i]):
-                    vec.append(r[j])
+                vec.extend(r[j] for j in range(degs[i]))
             return vector(vec)
 
-        def fr_V(vec): # to_O
+        def fr_V(vec):  # to_O
             vec = vec.list()
             pos = 0
             e = F(0)

src/sage/rings/padics/witt_vector.py

@@ -715,8 +715,7 @@ def _add_(self, other):
         G = []
         for n in range(self._prec):
             G_n = [self[n], other[n]]
-            for i in range(n):
-                G_n.append(P._eta_bar(G[i], n - i))
+            G_n.extend(P._eta_bar(G[i], n - i) for i in range(n))
             G.append(G_n)
         sum_vec = tuple(sum(G[i]) for i in range(self._prec))
 
@@ -753,8 +752,7 @@ def _mul_(self, other):
             G_n.extend(fast_char_p_power(self[i], p**(n - i))
                        * fast_char_p_power(other[n - i], p**i)
                        for i in range(1, n))
-            for i in range(n):
-                G_n.append(P._eta_bar(G[i], n - i))
+            G_n.extend(P._eta_bar(G[i], n - i) for i in range(n))
             G.append(G_n)
         prod_vec = tuple(sum(G[i]) for i in range(self._prec))
 

src/sage/rings/species.py

@@ -488,13 +488,10 @@ def __call__(self, *args):
                                  initial=0))
 
         # gens from self
-        gens = []
-        for gen in G.gens():
-            newgen = []
-            for cyc in gen.cycle_tuples():
-                for k in range(1, sum(Mlist[cyc[0] - 1].grade()) + 1):
-                    newgen.append(tuple([k + starts[i - 1] for i in cyc]))
-            gens.append(newgen)
+        gens = [[tuple([k + starts[i - 1] for i in cyc])
+                 for cyc in gen.cycle_tuples()
+                 for k in range(1, sum(Mlist[cyc[0] - 1].grade()) + 1)]
+                for gen in G.gens()]
 
         # gens from M_i and dompart
         P = args[0].parent()
@@ -503,9 +500,9 @@ def __call__(self, *args):
             K, K_dompart = M.permutation_group()
             for i, v in enumerate(K_dompart):
                 pi[i].extend([start + k for k in v])
-            for gen in K.gens():
-                gens.append([tuple([start + k for k in cyc])
-                             for cyc in gen.cycle_tuples()])
+            gens.extend([tuple([start + k for k in cyc])
+                         for cyc in gen.cycle_tuples()]
+                        for gen in K.gens())
 
         H = PermutationGroup(gens, domain=range(1, starts[-1] + 1))
         return P._indices(H, pi, check=False)