gh-40219: simplify the for loops in combinat (no parentheses)
    
by just removing some parentheses where they are useless

### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
    
URL: #40219
Reported by: Frédéric Chapoton
Reviewer(s): Travis Scrimshaw

Author: Release Manager

src/sage/combinat/alternating_sign_matrix.py

@@ -321,8 +321,8 @@ def inversion_number(self):
         inversion_num = 0
         asm_matrix = self.to_matrix()
         nonzero_cells = asm_matrix.nonzero_positions()
-        for (i, j) in nonzero_cells:
-            for (k, l) in nonzero_cells:
+        for i, j in nonzero_cells:
+            for k, l in nonzero_cells:
                 if i > k and j < l:
                     inversion_num += asm_matrix[i][j] * asm_matrix[k][l]
         return inversion_num
@@ -926,7 +926,7 @@ def to_permutation(self):
         if not self.is_permutation():
             raise ValueError('not a permutation matrix')
         asm_matrix = self.to_matrix()
-        return Permutation([j + 1 for (i, j) in asm_matrix.nonzero_positions()])
+        return Permutation([j + 1 for _, j in asm_matrix.nonzero_positions()])
 
     @combinatorial_map(name='to semistandard tableau')
     def to_semistandard_tableau(self):
@@ -1471,7 +1471,7 @@ def last(self):
         m.set_immutable()
         return self.element_class(self, m)
 
-    def _lattice_initializer(self):
+    def _lattice_initializer(self) -> tuple:
         r"""
         Return a 2-tuple to use in argument of ``LatticePoset``.
 
@@ -1492,7 +1492,7 @@ def _lattice_initializer(self):
         """
         mts, rels = MonotoneTriangles(self._n)._lattice_initializer()
         bij = {t: self.from_monotone_triangle(t) for t in mts}
-        return (bij.values(), [(bij[a], bij[b]) for (a, b) in rels])
+        return (bij.values(), [(bij[a], bij[b]) for a, b in rels])
 
     def cover_relations(self):
         r"""
@@ -1502,7 +1502,7 @@ def cover_relations(self):
         EXAMPLES::
 
             sage: A = AlternatingSignMatrices(3)
-            sage: for (a,b) in A.cover_relations():
+            sage: for a, b in A.cover_relations():
             ....:   eval('a, b')
             (
             [1 0 0]  [0 1 0]
@@ -1734,7 +1734,7 @@ def cover_relations(self):
         EXAMPLES::
 
             sage: M = MonotoneTriangles(3)
-            sage: for (a,b) in M.cover_relations():
+            sage: for a, b in M.cover_relations():
             ....:   eval('a, b')
             ([[3, 2, 1], [2, 1], [1]], [[3, 2, 1], [2, 1], [2]])
             ([[3, 2, 1], [2, 1], [1]], [[3, 2, 1], [3, 1], [1]])
@@ -1779,7 +1779,7 @@ def _is_a_cover(mt0, mt1):
         False
     """
     diffs = 0
-    for (a, b) in zip(flatten(mt0), flatten(mt1)):
+    for a, b in zip(flatten(mt0), flatten(mt1)):
         if a != b:
             if a + 1 == b:
                 diffs += 1

src/sage/combinat/bijectionist.py

@@ -59,7 +59,7 @@
     sage: def alpha1(p): return len(p.weak_excedences())
     sage: def alpha2(p): return len(p.fixed_points())
     sage: def beta1(p): return len(p.descents(final_descent=True)) if p else 0
-    sage: def beta2(p): return len([e for (e, f) in zip(p, p[1:]+[0]) if e == f+1])
+    sage: def beta2(p): return len([e for e, f in zip(p, p[1:]+[0]) if e == f+1])
     sage: tau = Permutation.longest_increasing_subsequence_length
     sage: def rotate_permutation(p):
     ....:     cycle = Permutation(tuple(range(1, len(p)+1)))
@@ -690,7 +690,7 @@ def set_statistics(self, *alpha_beta):
             sage: def wex(p): return len(p.weak_excedences())
             sage: def fix(p): return len(p.fixed_points())
             sage: def des(p): return len(p.descents(final_descent=True)) if p else 0
-            sage: def adj(p): return len([e for (e, f) in zip(p, p[1:]+[0]) if e == f+1])
+            sage: def adj(p): return len([e for e, f in zip(p, p[1:]+[0]) if e == f+1])
             sage: bij = Bijectionist(A, B, fix)
             sage: bij.set_statistics((wex, des), (len, len))
             sage: for solution in sorted(list(bij.solutions_iterator()), key=lambda d: tuple(sorted(d.items()))):
@@ -800,7 +800,7 @@ def statistics_fibers(self):
             sage: def wex(p): return len(p.weak_excedences())
             sage: def fix(p): return len(p.fixed_points())
             sage: def des(p): return len(p.descents(final_descent=True)) if p else 0
-            sage: def adj(p): return len([e for (e, f) in zip(p, p[1:]+[0]) if e == f+1])
+            sage: def adj(p): return len([e for e, f in zip(p, p[1:]+[0]) if e == f+1])
             sage: bij = Bijectionist(A, B, tau)
             sage: bij.set_statistics((len, len), (wex, des), (fix, adj))
             sage: table([[key, AB[0], AB[1]] for key, AB in bij.statistics_fibers().items()])
@@ -844,7 +844,7 @@ def statistics_table(self, header=True):
             sage: def wex(p): return len(p.weak_excedences())
             sage: def fix(p): return len(p.fixed_points())
             sage: def des(p): return len(p.descents(final_descent=True)) if p else 0
-            sage: def adj(p): return len([e for (e, f) in zip(p, p[1:]+[0]) if e == f+1])
+            sage: def adj(p): return len([e for e, f in zip(p, p[1:]+[0]) if e == f+1])
             sage: bij = Bijectionist(A, B, tau)
             sage: bij.set_statistics((wex, des), (fix, adj))
             sage: a, b = bij.statistics_table()
@@ -1553,7 +1553,7 @@ def _forced_constant_blocks(self):
             sage: def alpha1(p): return len(p.weak_excedences())
             sage: def alpha2(p): return len(p.fixed_points())
             sage: def beta1(p): return len(p.descents(final_descent=True)) if p else 0
-            sage: def beta2(p): return len([e for (e, f) in zip(p, p[1:] + [0]) if e == f + 1])
+            sage: def beta2(p): return len([e for e, f in zip(p, p[1:] + [0]) if e == f + 1])
             sage: tau = Permutation.longest_increasing_subsequence_length
             sage: def rotate_permutation(p):
             ....:    cycle = Permutation(tuple(range(1, len(p) + 1)))
@@ -3173,7 +3173,7 @@ def _non_copying_intersection(sets):
     sage: def alpha1(p): return len(p.weak_excedences())
     sage: def alpha2(p): return len(p.fixed_points())
     sage: def beta1(p): return len(p.descents(final_descent=True)) if p else 0
-    sage: def beta2(p): return len([e for (e, f) in zip(p, p[1:]+[0]) if e == f+1])
+    sage: def beta2(p): return len([e for e, f in zip(p, p[1:]+[0]) if e == f+1])
     sage: gamma = Permutation.longest_increasing_subsequence_length
     sage: def rotate_permutation(p):
     ....:    cycle = Permutation(tuple(range(1, len(p)+1)))

src/sage/combinat/chas/fsym.py

@@ -327,7 +327,7 @@ def duality_pairing(self, x, y):
 
                 sage: z = G[[1,3,5],[2,4]]
                 sage: all(F.duality_pairing(F[p1] * F[p2], z) == c
-                ....:     for ((p1, p2), c) in z.coproduct())
+                ....:     for (p1, p2), c in z.coproduct())
                 True
 
             TESTS:
@@ -341,7 +341,7 @@ def duality_pairing(self, x, y):
                 Rational Field
             """
             y = self.dual_basis()(y)
-            return self.base_ring().sum(coeff * y[t] for (t, coeff) in x)
+            return self.base_ring().sum(coeff * y[t] for t, coeff in x)
 
         def duality_pairing_matrix(self, basis, degree):
             r"""
@@ -1113,7 +1113,7 @@ def ascent_set(t):
         [2, 4, 5]
     """
     row_locations = {}
-    for (i, row) in enumerate(t):
+    for i, row in enumerate(t):
         for entry in row:
             row_locations[entry] = i
     n = len(row_locations)

src/sage/combinat/chas/wqsym.py

@@ -761,7 +761,7 @@ def algebraic_complement(self):
                 # for the formula we're using here.
                 Q = self.parent()
                 OSPs = Q.basis().keys()
-                return Q._from_dict({OSPs(A.reversed()): c for (A, c) in self},
+                return Q._from_dict({OSPs(A.reversed()): c for A, c in self},
                                     remove_zeros=False)
 
             def coalgebraic_complement(self):
@@ -798,7 +798,7 @@ def coalgebraic_complement(self):
                 # for the formula we're using here.
                 Q = self.parent()
                 OSPs = Q.basis().keys()
-                return Q._from_dict({OSPs(A.complement()): c for (A, c) in self},
+                return Q._from_dict({OSPs(A.complement()): c for A, c in self},
                                     remove_zeros=False)
 
             def star_involution(self):
@@ -834,7 +834,7 @@ def star_involution(self):
                 # for the formula we're using here.
                 Q = self.parent()
                 OSPs = Q.basis().keys()
-                return Q._from_dict({OSPs(A.complement().reversed()): c for (A, c) in self},
+                return Q._from_dict({OSPs(A.complement().reversed()): c for A, c in self},
                                     remove_zeros=False)
 
     X = Characteristic
@@ -1280,7 +1280,7 @@ def img(A):
                     return {OSPs(P): (one if (len(R) % 2 == len(P) % 2)
                                       else mine)
                             for R in Rs for P in R.strongly_fatter()}
-                return Q._from_dict(linear_combination((img(A), c) for (A, c) in self))
+                return Q._from_dict(linear_combination((img(A), c) for A, c in self))
 
             def coalgebraic_complement(self):
                 r"""
@@ -1328,7 +1328,7 @@ def img(A):
                     return {OSPs(P): (one if (len(R) % 2 == len(P) % 2)
                                       else mine)
                             for R in Rs for P in R.strongly_fatter()}
-                return Q._from_dict(linear_combination((img(A), c) for (A, c) in self))
+                return Q._from_dict(linear_combination((img(A), c) for A, c in self))
 
             def star_involution(self):
                 r"""
@@ -1363,7 +1363,7 @@ def star_involution(self):
                 # for the formula we're using here.
                 Q = self.parent()
                 OSPs = Q.basis().keys()
-                return Q._from_dict({OSPs(A.complement().reversed()): c for (A, c) in self},
+                return Q._from_dict({OSPs(A.complement().reversed()): c for A, c in self},
                                     remove_zeros=False)
 
     Q = StronglyCoarser
@@ -1633,7 +1633,7 @@ def product_on_basis(self, x, y):
                 return self.monomial(x)
             xlist = [(j, (k == 0))
                      for part in x
-                     for (k, j) in enumerate(sorted(part))]
+                     for k, j in enumerate(sorted(part))]
             # xlist is a list of the form
             # [(e_1, s_1), (e_2, s_2), ..., (e_n, s_n)],
             # where e_1, e_2, ..., e_n are the entries of the parts of
@@ -1643,7 +1643,7 @@ def product_on_basis(self, x, y):
             m = max(max(part) for part in x)  # The degree of x
             ylist = [(m + j, (k == 0))
                      for part in y
-                     for (k, j) in enumerate(sorted(part))]
+                     for k, j in enumerate(sorted(part))]
             # ylist is like xlist, but for y instead of x, and with
             # a shift by m.
 
@@ -1748,7 +1748,7 @@ def standardize(P):  # standardize an ordered set partition
                     deconcatenates.append((left, right))
             T = self.tensor_square()
             return T.sum_of_monomials((standardize(left), standardize(right))
-                                      for (left, right) in deconcatenates)
+                                      for left, right in deconcatenates)
 
         class Element(WQSymBasis_abstract.Element):
             def algebraic_complement(self):
@@ -1797,7 +1797,7 @@ def img(A):
                     return {OSPs(P): (one if (len(R) % 2 == len(P) % 2)
                                       else mine)
                             for R in Rs for P in R.strongly_finer()}
-                return Phi._from_dict(linear_combination((img(A), c) for (A, c) in self))
+                return Phi._from_dict(linear_combination((img(A), c) for A, c in self))
 
             def coalgebraic_complement(self):
                 r"""
@@ -1845,7 +1845,7 @@ def img(A):
                     return {OSPs(P): (one if (len(R) % 2 == len(P) % 2)
                                       else mine)
                             for R in Rs for P in R.strongly_finer()}
-                return Phi._from_dict(linear_combination((img(A), c) for (A, c) in self))
+                return Phi._from_dict(linear_combination((img(A), c) for A, c in self))
 
             def star_involution(self):
                 r"""
@@ -1880,7 +1880,7 @@ def star_involution(self):
                 # for the formula we're using here.
                 Phi = self.parent()
                 OSPs = Phi.basis().keys()
-                return Phi._from_dict({OSPs(A.complement().reversed()): c for (A, c) in self},
+                return Phi._from_dict({OSPs(A.complement().reversed()): c for A, c in self},
                                       remove_zeros=False)
 
     Phi = StronglyFiner
@@ -2262,7 +2262,7 @@ def algebraic_complement(self):
             # complement componentwise, then convert back.
             parent = self.parent()
             M = parent.realization_of().M()
-            dct = {I.reversed(): coeff for (I, coeff) in M(self)}
+            dct = {I.reversed(): coeff for I, coeff in M(self)}
             return parent(M._from_dict(dct, remove_zeros=False))
 
         def coalgebraic_complement(self):
@@ -2427,7 +2427,7 @@ def coalgebraic_complement(self):
             # complement componentwise, then convert back.
             parent = self.parent()
             M = parent.realization_of().M()
-            dct = {I.complement(): coeff for (I, coeff) in M(self)}
+            dct = {I.complement(): coeff for I, coeff in M(self)}
             return parent(M._from_dict(dct, remove_zeros=False))
 
         def star_involution(self):
@@ -2555,7 +2555,7 @@ def star_involution(self):
             # complement componentwise, then convert back.
             parent = self.parent()
             M = parent.realization_of().M()
-            dct = {I.reversed().complement(): coeff for (I, coeff) in M(self)}
+            dct = {I.reversed().complement(): coeff for I, coeff in M(self)}
             return parent(M._from_dict(dct, remove_zeros=False))
 
         def to_quasisymmetric_function(self):
@@ -2597,4 +2597,4 @@ def to_quasisymmetric_function(self):
             M = QuasiSymmetricFunctions(self.parent().base_ring()).Monomial()
             MW = self.parent().realization_of().M()
             return M.sum_of_terms((i.to_composition(), coeff)
-                                  for (i, coeff) in MW(self))
+                                  for i, coeff in MW(self))