From 94f80bb8ed5d9a0e9bec288617d084eda60cba4e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Chapoton?= <chapoton@unistra.fr>
Date: Sat, 7 Sep 2024 18:49:53 +0200
Subject: [PATCH] fixing most ruff PERF4 warnings in combinat

---
 src/sage/combinat/composition_tableau.py      |  5 +---
 src/sage/combinat/diagram.py                  |  9 +++----
 src/sage/combinat/diagram_algebras.py         | 10 ++++----
 src/sage/combinat/dlx.py                      |  5 +---
 src/sage/combinat/finite_state_machine.py     |  6 ++---
 src/sage/combinat/free_dendriform_algebra.py  | 10 ++++----
 src/sage/combinat/free_prelie_algebra.py      | 10 ++++----
 src/sage/combinat/gelfand_tsetlin_patterns.py | 24 +++++++------------
 src/sage/combinat/graph_path.py               |  6 +----
 src/sage/combinat/integer_vector.py           | 10 ++++----
 src/sage/combinat/knutson_tao_puzzles.py      |  9 +++----
 src/sage/combinat/misc.py                     |  8 ++-----
 src/sage/combinat/parallelogram_polyomino.py  | 14 ++++-------
 src/sage/combinat/partition_algebra.py        | 13 ++++------
 src/sage/combinat/ribbon_shaped_tableau.py    | 11 ++++-----
 src/sage/combinat/rsk.py                      |  6 ++---
 src/sage/combinat/shifted_primed_tableau.py   |  8 ++++---
 src/sage/combinat/skew_partition.py           | 21 +++++++---------
 src/sage/combinat/skew_tableau.py             | 23 ++++++++----------
 src/sage/combinat/specht_module.py            | 18 +++++---------
 src/sage/combinat/symmetric_group_algebra.py  | 12 ++++------
 src/sage/combinat/tableau.py                  | 22 ++++++++---------
 src/sage/combinat/tableau_tuple.py            | 11 ++++-----
 23 files changed, 103 insertions(+), 168 deletions(-)

diff --git a/src/sage/combinat/composition_tableau.py b/src/sage/combinat/composition_tableau.py
index e90fe55f6a5..1e05da84c4e 100644
--- a/src/sage/combinat/composition_tableau.py
+++ b/src/sage/combinat/composition_tableau.py
@@ -211,10 +211,7 @@ def descent_set(self):
             sage: CompositionTableau([[1],[3,2],[4,4]]).descent_set()
             [1, 3]
         """
-        cols = {}
-        for row in self:
-            for col, i in enumerate(row):
-                cols[i] = col
+        cols = {i: col for row in self for col, i in enumerate(row)}
         return sorted(i for i in cols if i + 1 in cols and cols[i + 1] >= cols[i])
 
     def descent_composition(self):
diff --git a/src/sage/combinat/diagram.py b/src/sage/combinat/diagram.py
index f5b8f9ad864..cc3c1dfe0b6 100644
--- a/src/sage/combinat/diagram.py
+++ b/src/sage/combinat/diagram.py
@@ -336,12 +336,9 @@ def _latex_(self):
 
         lr = r'\def\lr#1{\multicolumn{1}{|@{\hspace{.6ex}}c@{\hspace{.6ex}}|}{\raisebox{-.3ex}{$#1$}}}'
 
-        array = []
-        for i in range(self._n_rows):
-            row = []
-            for j in range(self._n_cols):
-                row.append("\\phantom{x}" if (i, j) in self else None)
-            array.append(row)
+        array = [[("\\phantom{x}" if (i, j) in self else None)
+                  for j in range(self._n_cols)]
+                 for i in range(self._n_rows)]
 
         def end_line(r):
             # give the line ending to row ``r``
diff --git a/src/sage/combinat/diagram_algebras.py b/src/sage/combinat/diagram_algebras.py
index 364a55c74c9..6410a4a93ea 100644
--- a/src/sage/combinat/diagram_algebras.py
+++ b/src/sage/combinat/diagram_algebras.py
@@ -3013,7 +3013,7 @@ def jucys_murphy_element(self, i):
             sage: L = [P.L(i/2) for i in range(1,2*k+1)]
             sage: all(x.dual() == x for x in L)
             True
-            sage: all(x * y == y * x for x in L for y in L)  # long time
+            sage: all(x * y == y * x for x, y in Subsets(L, 2))  # long time
             True
             sage: Lsum = sum(L)
             sage: gens = [P.s(i) for i in range(1,k)]
@@ -3045,13 +3045,13 @@ def jucys_murphy_element(self, i):
 
         The same tests for a half integer partition algebra::
 
-            sage: k = 9/2
+            sage: k = 7/2
             sage: R.<n> = QQ[]
             sage: P = PartitionAlgebra(k, n)
             sage: L = [P.L(i/2) for i in range(1,2*k+1)]
             sage: all(x.dual() == x for x in L)
             True
-            sage: all(x * y == y * x for x in L for y in L)  # long time
+            sage: all(x * y == y * x for x, y in Subsets(L, 2))  # long time
             True
             sage: Lsum = sum(L)
             sage: gens = [P.s(i) for i in range(1,k-1/2)]
@@ -5847,11 +5847,9 @@ def to_Brauer_partition(l, k=None):
         True
     """
     L = to_set_partition(l, k=k)
-    L2 = []
     paired = []
     not_paired = []
-    for i in L:
-        L2.append(list(i))
+    L2 = (list(i) for i in L)
     for i in L2:
         if len(i) > 2:
             raise ValueError("blocks must have size at most 2, but {} has {}".format(i, len(i)))
diff --git a/src/sage/combinat/dlx.py b/src/sage/combinat/dlx.py
index 383dda056be..d25f7414d0d 100644
--- a/src/sage/combinat/dlx.py
+++ b/src/sage/combinat/dlx.py
@@ -484,10 +484,7 @@ def AllExactCovers(M):
     ones = []
     r = 1    # damn 1-indexing
     for R in M.rows():
-        row = []
-        for i in range(len(R)):
-            if R[i]:
-                row.append(i + 1)  # damn 1-indexing
+        row = [i for i, Ri in enumerate(R, start=1) if Ri]
         ones.append([r, row])
         r += 1
     for s in DLXMatrix(ones):
diff --git a/src/sage/combinat/finite_state_machine.py b/src/sage/combinat/finite_state_machine.py
index 96d35859873..2750ea15e9c 100644
--- a/src/sage/combinat/finite_state_machine.py
+++ b/src/sage/combinat/finite_state_machine.py
@@ -9437,9 +9437,9 @@ def graph(self, edge_labels='words_in_out'):
             transitions = state.transitions
             if not transitions:
                 isolated_vertices.append(state.label())
-            for t in transitions:
-                graph_data.append((t.from_state.label(), t.to_state.label(),
-                                   label_fct(t)))
+            graph_data.extend((t.from_state.label(), t.to_state.label(),
+                               label_fct(t))
+                              for t in transitions)
 
         G = DiGraph(graph_data, multiedges=True, loops=True)
         G.add_vertices(isolated_vertices)
diff --git a/src/sage/combinat/free_dendriform_algebra.py b/src/sage/combinat/free_dendriform_algebra.py
index 2acfee1b337..4be2c514778 100644
--- a/src/sage/combinat/free_dendriform_algebra.py
+++ b/src/sage/combinat/free_dendriform_algebra.py
@@ -939,14 +939,12 @@ def merge(self, other):
                 return self
             ret = list(self.vars)
             cur_vars = set(ret)
-            for v in other.vars:
-                if v not in cur_vars:
-                    ret.append(v)
+            ret.extend(v for v in other.vars if v not in cur_vars)
             return DendriformFunctor(Alphabet(ret))
-        else:
-            return None
 
-    def _repr_(self):
+        return None
+
+    def _repr_(self) -> str:
         """
         TESTS::
 
diff --git a/src/sage/combinat/free_prelie_algebra.py b/src/sage/combinat/free_prelie_algebra.py
index 1ea7d3274a1..6e7525d8b23 100644
--- a/src/sage/combinat/free_prelie_algebra.py
+++ b/src/sage/combinat/free_prelie_algebra.py
@@ -1023,14 +1023,12 @@ def merge(self, other):
                 return self
             ret = list(self.vars)
             cur_vars = set(ret)
-            for v in other.vars:
-                if v not in cur_vars:
-                    ret.append(v)
+            ret.extend(v for v in other.vars if v not in cur_vars)
             return PreLieFunctor(Alphabet(ret))
-        else:
-            return None
 
-    def _repr_(self):
+        return None
+
+    def _repr_(self) -> str:
         """
         TESTS::
 
diff --git a/src/sage/combinat/gelfand_tsetlin_patterns.py b/src/sage/combinat/gelfand_tsetlin_patterns.py
index be4e236b099..5c3c485e549 100644
--- a/src/sage/combinat/gelfand_tsetlin_patterns.py
+++ b/src/sage/combinat/gelfand_tsetlin_patterns.py
@@ -302,11 +302,9 @@ def boxed_entries(self) -> tuple:
             sage: G.boxed_entries()
             ((1, 0),)
         """
-        ret = []
-        for i in range(1, len(self)):
-            for j in range(len(self[i])):
-                if self[i][j] == self[i - 1][j]:
-                    ret.append((i, j))
+        ret = [(i, j) for i in range(1, len(self))
+               for j, selfij in enumerate(self[i])
+               if selfij == self[i - 1][j]]
         return tuple(ret)
 
     @cached_method
@@ -324,11 +322,9 @@ def circled_entries(self) -> tuple:
             sage: G.circled_entries()
             ((1, 1), (2, 0))
         """
-        ret = []
-        for i in range(1, len(self)):
-            for j in range(len(self[i])):
-                if self[i][j] == self[i - 1][j + 1]:
-                    ret.append((i, j))
+        ret = [(i, j) for i in range(1, len(self))
+               for j, selfij in enumerate(self[i])
+               if selfij == self[i - 1][j + 1]]
         return tuple(ret)
 
     @cached_method
@@ -349,11 +345,9 @@ def special_entries(self) -> tuple:
             sage: G.special_entries()
             ((2, 0),)
         """
-        ret = []
-        for i in range(1, len(self)):
-            for j in range(len(self[i])):
-                if self[i-1][j] > self[i][j] and self[i][j] > self[i-1][j+1]:
-                    ret.append((i, j))
+        ret = [(i, j) for i in range(1, len(self))
+               for j, selfij in enumerate(self[i])
+               if self[i - 1][j] > selfij > self[i - 1][j + 1]]
         return tuple(ret)
 
     def number_of_boxes(self) -> int:
diff --git a/src/sage/combinat/graph_path.py b/src/sage/combinat/graph_path.py
index 2fb255579dd..df84b1acdf7 100644
--- a/src/sage/combinat/graph_path.py
+++ b/src/sage/combinat/graph_path.py
@@ -236,11 +236,7 @@ def paths_from_source_to_target(self, source, target):
             [[2, 3, 4], [2, 4]]
         """
         source_paths = self.outgoing_paths(source)
-        paths = []
-        for path in source_paths:
-            if path[-1] == target:
-                paths.append(path)
-        return paths
+        return [path for path in source_paths if path[-1] == target]
 
     def paths(self):
         """
diff --git a/src/sage/combinat/integer_vector.py b/src/sage/combinat/integer_vector.py
index 516d2114ffc..6848609cf5d 100644
--- a/src/sage/combinat/integer_vector.py
+++ b/src/sage/combinat/integer_vector.py
@@ -1174,19 +1174,17 @@ def _list_rec(self, n, k):
         EXAMPLES::
 
             sage: IV = IntegerVectors(2,3)
-            sage: IV._list_rec(2,3)
+            sage: list(IV._list_rec(2,3))
             [(2, 0, 0), (1, 1, 0), (1, 0, 1), (0, 2, 0), (0, 1, 1), (0, 0, 2)]
         """
-        res = []
-
         if k == 1:
-            return [(n, )]
+            yield (n,)
+            return
 
         for nbar in range(n + 1):
             n_diff = n - nbar
             for rest in self._list_rec(nbar, k - 1):
-                res.append((n_diff,) + rest)
-        return res
+                yield (n_diff,) + rest
 
     def __iter__(self):
         """
diff --git a/src/sage/combinat/knutson_tao_puzzles.py b/src/sage/combinat/knutson_tao_puzzles.py
index e1e4f746f42..f7a7c513c52 100644
--- a/src/sage/combinat/knutson_tao_puzzles.py
+++ b/src/sage/combinat/knutson_tao_puzzles.py
@@ -2064,12 +2064,9 @@ def _fill_piece(self, nw_label, ne_label, pieces) -> list[PuzzlePiece]:
             sage: ps._fill_piece('0', '0', ps._bottom_deltas)
             [0/0\0]
         """
-        output = []
-        for piece in pieces:
-            if (piece['north_west'] == nw_label and
-                    piece['north_east'] == ne_label):
-                output.append(piece)
-        return output
+        return [piece for piece in pieces
+                if (piece['north_west'] == nw_label and
+                    piece['north_east'] == ne_label)]
 
     @cached_method
     def _fill_strip(self, nw_labels, ne_label, pieces, final_pieces=None):
diff --git a/src/sage/combinat/misc.py b/src/sage/combinat/misc.py
index 404c032a8dc..d04b615be80 100644
--- a/src/sage/combinat/misc.py
+++ b/src/sage/combinat/misc.py
@@ -202,11 +202,7 @@ def _monomial_exponent_to_lower_factorial(me, x):
         sage: _monomial_exponent_to_lower_factorial(([2,2,2]),a)
         x^2*y^2*z^2 - x^2*y^2*z - x^2*y*z^2 - x*y^2*z^2 + x^2*y*z + x*y^2*z + x*y*z^2 - x*y*z
     """
-    terms = []
-    for i in range(len(me)):
-        for j in range(me[i]):
-            terms.append( x[i]-j )
-    return prod(terms)
+    return prod(x[i] - j for i, mei in enumerate(me) for j in range(mei))
 
 
 def umbral_operation(poly):
@@ -235,7 +231,7 @@ def umbral_operation(poly):
     exponents = poly.exponents()
     coefficients = poly.coefficients()
     length = len(exponents)
-    return sum( [coefficients[i]*_monomial_exponent_to_lower_factorial(exponents[i],x) for i in range(length)] )
+    return sum(coefficients[i]*_monomial_exponent_to_lower_factorial(exponents[i], x) for i in range(length))
 
 
 class IterableFunctionCall:
diff --git a/src/sage/combinat/parallelogram_polyomino.py b/src/sage/combinat/parallelogram_polyomino.py
index ed9308e82e9..c60c72c10d2 100644
--- a/src/sage/combinat/parallelogram_polyomino.py
+++ b/src/sage/combinat/parallelogram_polyomino.py
@@ -1974,12 +1974,9 @@ def widths(self) -> list:
             sage: pp.widths()
             []
         """
-        widths = []
         uw = self.upper_widths()
         lw = self.lower_widths()
-        for i in range(len(lw)):
-            widths.append(uw[i] - lw[i])
-        return widths
+        return [up - lo for up, lo in zip(uw, lw)]
 
     def degree_convexity(self) -> int:
         r"""
@@ -3387,11 +3384,10 @@ def get_BS_nodes(self):
             sage: pp.set_options(drawing_components=dict(tree=True))
             sage: view(pp) # not tested
         """
-        result = []
-        for h in range(1, self.height()):
-            result.append(self._get_node_position_at_row(h))
-        for w in range(1, self.width()):
-            result.append(self._get_node_position_at_column(w))
+        result = [self._get_node_position_at_row(h)
+                  for h in range(1, self.height())]
+        result.extend(self._get_node_position_at_column(w)
+                      for w in range(1, self.width()))
         return result
 
     def get_right_BS_nodes(self):
diff --git a/src/sage/combinat/partition_algebra.py b/src/sage/combinat/partition_algebra.py
index f0d15115ac9..91e79be4cbc 100644
--- a/src/sage/combinat/partition_algebra.py
+++ b/src/sage/combinat/partition_algebra.py
@@ -364,9 +364,7 @@ def __iter__(self):
             True
         """
         for p in Permutations(self.k):
-            res = []
-            for i in range(self.k):
-                res.append(Set([i + 1, -p[i]]))
+            res = [Set([i, -pi]) for i, pi in enumerate(p, start=1)]
             yield self.element_class(self, res)
 
 
@@ -433,10 +431,7 @@ def __iter__(self):
              {{1, -3}, {2, -2}, {4, -4}, {3, -1}}]
         """
         for p in Permutations(self.k):
-            res = []
-            for i in range(self.k):
-                res.append(Set([i + 1, -p[i]]))
-
+            res = [Set([i, -pi]) for i, pi in enumerate(p, start=1)]
             res.append(Set([self.k + 1, -self.k - 1]))
             yield self.element_class(self, res)
 
@@ -1941,8 +1936,8 @@ def to_set_partition(l, k=None):
         to_be_added -= spart
         sp.append(spart)
 
-    for singleton in to_be_added:
-        sp.append(Set([singleton]))
+    sp.extend(Set([singleton])
+              for singleton in to_be_added)
 
     return Set(sp)
 
diff --git a/src/sage/combinat/ribbon_shaped_tableau.py b/src/sage/combinat/ribbon_shaped_tableau.py
index d33cc115396..dd7218c899c 100644
--- a/src/sage/combinat/ribbon_shaped_tableau.py
+++ b/src/sage/combinat/ribbon_shaped_tableau.py
@@ -350,18 +350,17 @@ def from_permutation(self, p):
              [[1, 2], [3]],
              [[1], [2], [3]]]
         """
-        if p == []:
+        if not p:
             return self.element_class(self, [])
 
         comp = p.descents()
 
-        if comp == []:
+        if not comp:
             return self.element_class(self, [p[:]])
 
-        r = []
-        r.append([p[j] for j in range(comp[0])])
-        for i in range(len(comp) - 1):
-            r.append([p[j] for j in range(comp[i], comp[i + 1])])
+        r = [[p[j] for j in range(comp[0])]]
+        r.extend([p[j] for j in range(comp[i], comp[i + 1])]
+                 for i in range(len(comp) - 1))
         r.append([p[j] for j in range(comp[-1], len(p))])
         r.reverse()
         return self.element_class(self, r)
diff --git a/src/sage/combinat/rsk.py b/src/sage/combinat/rsk.py
index 5e276d5ebcf..1fa0ba62b4e 100644
--- a/src/sage/combinat/rsk.py
+++ b/src/sage/combinat/rsk.py
@@ -2957,12 +2957,10 @@ def _backward_format_output(self, obj1, obj2, output):
                 if j == 0:
                     df.append([])
                 if j > 0 and obj1[j] < obj1[j-1]:
-                    for _ in range(obj1[j-1]-obj1[j]):
-                        df.append([])
+                    df.extend([] for _ in range(obj1[j-1]-obj1[j]))
                 df[-1].append(obj2[j])
             if obj1:
-                for a in range(obj1[-1]-1):
-                    df.append([])
+                df.extend([] for a in range(obj1[-1]-1))
             # If biword is empty, return a decreasing factorization with 1 factor
             else:
                 df.append([])
diff --git a/src/sage/combinat/shifted_primed_tableau.py b/src/sage/combinat/shifted_primed_tableau.py
index 37bbd402c14..6d889425d28 100644
--- a/src/sage/combinat/shifted_primed_tableau.py
+++ b/src/sage/combinat/shifted_primed_tableau.py
@@ -2716,9 +2716,11 @@ def _add_strip(sub_tab, full_tab, length):
             if sub_tab and len(sub_tab) < len(full_tab):
                 plat_list.append(min(sub_tab[-1] + primed_strip[-2] - 1,
                                      full_tab[len(sub_tab)]))
-            for row in reversed(range(1, len(sub_tab))):
-                plat_list.append(min(sub_tab[row-1]+primed_strip[row-1]-1, full_tab[row])
-                                 - sub_tab[row] - primed_strip[row])
+            plat_list.extend(
+                min(sub_tab[row-1] + primed_strip[row-1] - 1, full_tab[row])
+                - sub_tab[row] - primed_strip[row]
+                for row in reversed(range(1, len(sub_tab))))
+
             if sub_tab:
                 plat_list.append(full_tab[0] - sub_tab[0] - primed_strip[0])
             else:
diff --git a/src/sage/combinat/skew_partition.py b/src/sage/combinat/skew_partition.py
index bee333dc9a5..aad38f9afbf 100644
--- a/src/sage/combinat/skew_partition.py
+++ b/src/sage/combinat/skew_partition.py
@@ -1032,12 +1032,9 @@ def cells(self):
         """
         outer = self.outer()
         inner = self.inner()[:]
-        inner += [0]*(len(outer)-len(inner))
-        res = []
-        for i in range(len(outer)):
-            for j in range(inner[i], outer[i]):
-                res.append( (i,j) )
-        return res
+        inner += [0] * (len(outer) - len(inner))
+        return [(i, j) for i, outi in enumerate(outer)
+                for j in range(inner[i], outi)]
 
     def to_list(self):
         """
@@ -1148,15 +1145,13 @@ def rows_intersection_set(self):
             sage: skp.rows_intersection_set() == cells
             True
         """
-        res = []
         outer = self.outer()
         inner = self.inner()
-        inner += [0] * int(len(outer)-len(inner))
+        inner += [0] * (len(outer) - len(inner))
 
-        for i in range(len(outer)):
-            for j in range(outer[i]):
-                if outer[i] != inner[i]:
-                    res.append((i,j))
+        res = [(i, j) for i, outi in enumerate(outer)
+               for j in range(outi)
+               if outi != inner[i]]
         return Set(res)
 
     def columns_intersection_set(self):
@@ -1238,7 +1233,7 @@ def jacobi_trudi(self):
         h = SymmetricFunctions(QQ).homogeneous()
         H = MatrixSpace(h, nn)
 
-        q = q + [0]*int(nn-len(q))
+        q = q + [0] * (nn - len(q))
         m = []
         for i in range(1,nn+1):
             row = []
diff --git a/src/sage/combinat/skew_tableau.py b/src/sage/combinat/skew_tableau.py
index ca57594ed71..44189013d5c 100644
--- a/src/sage/combinat/skew_tableau.py
+++ b/src/sage/combinat/skew_tableau.py
@@ -1172,10 +1172,10 @@ def row_stabilizer(self):
         # tableau, by including the identity permutation on the set [1..k].
         k = self.size()
         gens = [list(range(1, k + 1))]
-        for row in self:
-            for j in range(len(row) - 1):
-                if row[j] is not None:
-                    gens.append((row[j], row[j + 1]))
+        gens.extend((row[j], row[j + 1])
+                    for row in self
+                    for j in range(len(row) - 1)
+                    if row[j] is not None)
         return PermutationGroup(gens)
 
     def column_stabilizer(self):
@@ -1777,12 +1777,10 @@ def cells(self):
             sage: s.cells()
             [(0, 1), (0, 2), (1, 0), (2, 0)]
         """
-        res = []
-        for i in range(len(self)):
-            for j in range(len(self[i])):
-                if self[i][j] is not None:
-                    res.append((i, j))
-        return res
+        return [(i, j)
+                for i, selfi in enumerate(self)
+                for j in range(len(selfi))
+                if selfi[j] is not None]
 
     def cells_containing(self, i):
         r"""
@@ -1950,12 +1948,11 @@ def from_expr(self, expr):
             sage: SkewTableaux().from_expr([[1,1],[[5],[3,4],[1,2]]])
             [[None, 1, 2], [None, 3, 4], [5]]
         """
-        skp = []
         outer = expr[1]
         inner = expr[0] + [0] * (len(outer) - len(expr[0]))
 
-        for i in range(len(outer)):
-            skp.append([None] * (inner[i]) + outer[-(i + 1)])
+        skp = [[None] * (inner[i]) + outer[-(i + 1)]
+               for i in range(len(outer))]
 
         return self.element_class(self, skp)
 
diff --git a/src/sage/combinat/specht_module.py b/src/sage/combinat/specht_module.py
index 0114a8f191b..1af53083f89 100644
--- a/src/sage/combinat/specht_module.py
+++ b/src/sage/combinat/specht_module.py
@@ -1146,18 +1146,12 @@ def _to_diagram(D):
     if isinstance(D, Diagram):
         return D
     if D in _Partitions:
-        D = _Partitions(D).cells()
-    elif D in SkewPartitions():
-        D = SkewPartitions()(D).cells()
-    elif D in IntegerVectors():
-        cells = []
-        for i, row in enumerate(D):
-            for j in range(row):
-                cells.append((i, j))
-        D = cells
-    else:
-        D = [tuple(cell) for cell in D]
-    return D
+        return _Partitions(D).cells()
+    if D in SkewPartitions():
+        return SkewPartitions()(D).cells()
+    if D in IntegerVectors():
+        return [(i, j) for i, row in enumerate(D) for j in range(row)]
+    return [tuple(cell) for cell in D]
 
 
 def specht_module_spanning_set(D, SGA=None):
diff --git a/src/sage/combinat/symmetric_group_algebra.py b/src/sage/combinat/symmetric_group_algebra.py
index b9ea545cd60..47820fc23a5 100644
--- a/src/sage/combinat/symmetric_group_algebra.py
+++ b/src/sage/combinat/symmetric_group_algebra.py
@@ -1043,10 +1043,8 @@ def central_orthogonal_idempotents(self):
 
             - :meth:`central_orthogonal_idempotent`
         """
-        out = []
-        for key in sorted(self._blocks_dictionary, reverse=True):
-            out.append(self.central_orthogonal_idempotent(key))
-        return out
+        return [self.central_orthogonal_idempotent(key)
+                for key in sorted(self._blocks_dictionary, reverse=True)]
 
     def central_orthogonal_idempotent(self, la, block=True):
         r"""
@@ -2016,9 +2014,9 @@ def seminormal_basis(self, mult='l2r'):
         basis = []
         for part in Partitions_n(self.n):
             stp = StandardTableaux_shape(part)
-            for t1 in stp:
-                for t2 in stp:
-                    basis.append(self.epsilon_ik(t1, t2, mult=mult))
+            basis.extend(self.epsilon_ik(t1, t2, mult=mult)
+                         for t1 in stp
+                         for t2 in stp)
         return basis
 
     def dft(self, form=None, mult='l2r'):
diff --git a/src/sage/combinat/tableau.py b/src/sage/combinat/tableau.py
index 19f9033fcea..80e3391b279 100644
--- a/src/sage/combinat/tableau.py
+++ b/src/sage/combinat/tableau.py
@@ -1148,12 +1148,10 @@ def descents(self):
             sage: Tableau( [[1,2,3],[4,5]] ).descents()
             [(1, 0), (1, 1)]
         """
-        descents = []
-        for i in range(1, len(self)):
-            for j in range(len(self[i])):
-                if self[i][j] > self[i-1][j]:
-                    descents.append((i, j))
-        return descents
+        return [(i, j)
+                for i in range(1, len(self))
+                for j, selfij in enumerate(self[i])
+                if selfij > self[i-1][j]]
 
     def major_index(self):
         """
@@ -1214,15 +1212,15 @@ def inversions(self):
             for j, entry in enumerate(row):
                 # c is in position (i,j)
                 # find the d that satisfy condition 1
-                for k in range(j+1, len(row)):
-                    if entry > row[k]:
-                        inversions.append(((i, j), (i, k)))
+                inversions.extend(((i, j), (i, k))
+                                  for k in range(j + 1, len(row))
+                                  if entry > row[k])
                 # find the d that satisfy condition 2
                 if i == 0:
                     continue
-                for k in range(j):
-                    if entry > previous_row[k]:
-                        inversions.append(((i, j), (i-1, k)))
+                inversions.extend(((i, j), (i - 1, k))
+                                  for k in range(j)
+                                  if entry > previous_row[k])
             previous_row = row
         return inversions
 
diff --git a/src/sage/combinat/tableau_tuple.py b/src/sage/combinat/tableau_tuple.py
index a24ac5ca809..fd847c4ad1e 100644
--- a/src/sage/combinat/tableau_tuple.py
+++ b/src/sage/combinat/tableau_tuple.py
@@ -1084,10 +1084,8 @@ def row_stabilizer(self):
         # tableau, by including the identity permutation on the set [1..n].
         n = max(self.entries())
         gens = [list(range(1, n + 1))]
-        for t in self:
-            for i in range(len(t)):
-                for j in range(len(t[i]) - 1):
-                    gens.append((t[i][j], t[i][j + 1]))
+        gens.extend((ti[j], ti[j + 1]) for t in self
+                    for ti in t for j in range(len(ti) - 1))
         return PermutationGroup(gens)
 
     def column_stabilizer(self):
@@ -2644,11 +2642,10 @@ def an_element(self):
             ([[1, 2]], [], [])
         """
         if self.size() == 0:
-            return self.element_class(self, [[] for _ in range(self.level())])
+            return self.element_class(self, [[]] * self.level())
 
         tab = [[list(range(1, self.size() + 1))]]
-        for _ in range(self.level() - 1):
-            tab.append([])
+        tab.extend([] for _ in range(self.level() - 1))
         return self.element_class(self, tab)