gh-39972: some fixes for ruff C4
    
mostly about dict comprehensions

### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
    
URL: #39972
Reported by: Frédéric Chapoton
Reviewer(s): Dima Pasechnik

Author: Release Manager

src/sage/algebras/free_algebra.py

@@ -1670,7 +1670,7 @@ def merge(self, other):
                 o_degs = [1] * len(other.vars)
             else:
                 o_degs = list(other.degs)
-            self_table = {w: d for w, d in zip(self.vars, deg)}
+            self_table = dict(zip(self.vars, deg))
             for v, d in zip(other.vars, o_degs):
                 if v not in self_vars:
                     deg.append(d)

src/sage/combinat/root_system/ambient_space.py

@@ -193,7 +193,7 @@ def __call__(self, v):
         # This adds coercion from a list
         if isinstance(v, (list, tuple)):
             K = self.base_ring()
-            return self._from_dict(dict((i,K(c)) for i,c in enumerate(v) if c))
+            return self._from_dict({i: K(c) for i, c in enumerate(v) if c})
         else:
             return CombinatorialFreeModule.__call__(self, v)
 

src/sage/combinat/root_system/cartan_type.py

@@ -1739,10 +1739,10 @@ def symmetrizer(self):
         from sage.matrix.constructor import matrix, diagonal_matrix
         m = self.cartan_matrix()
         n = m.nrows()
-        M = matrix(ZZ, n, n*n, sparse=True)
-        for (i,j) in m.nonzero_positions():
-            M[i, n * i + j] = m[i,j]
-            M[j, n * i + j] -= m[j,i]
+        M = matrix(ZZ, n, n * n, sparse=True)
+        for i, j in m.nonzero_positions():
+            M[i, n * i + j] = m[i, j]
+            M[j, n * i + j] -= m[j, i]
         kern = M.integer_kernel()
         c = len(self.dynkin_diagram().connected_components(sort=False))
         if kern.dimension() < c:
@@ -1757,7 +1757,7 @@ def symmetrizer(self):
         D = sum(kern.basis())
         assert diagonal_matrix(D) * m == m.transpose() * diagonal_matrix(D)
         I = self.index_set()
-        return Family( dict( (I[i], D[i]) for i in range(n) ) )
+        return Family({I[i]: D[i] for i in range(n)})
 
     def index_set_bipartition(self):
         r"""
@@ -2131,7 +2131,7 @@ def row_annihilator(self, m=None):
             raise ValueError("the kernel is not 1 dimensional")
         assert (all(coef > 0 for coef in annihilator_basis[0]))
 
-        return Family(dict((i,annihilator_basis[0][i])for i in self.index_set()))
+        return Family({i: annihilator_basis[0][i] for i in self.index_set()})
 
     acheck = row_annihilator
 
@@ -2205,8 +2205,8 @@ def c(self):
         """
         a = self.a()
         acheck = self.acheck()
-        return Family(dict((i, max(ZZ(1), a[i] // acheck[i]))
-                           for i in self.index_set()))
+        return Family({i: max(ZZ.one(), a[i] // acheck[i])
+                       for i in self.index_set()})
 
     def translation_factors(self):
         r"""
@@ -2372,21 +2372,21 @@ def translation_factors(self):
 
         REFERENCES:
 
-        .. [HST09] \F. Hivert, A. Schilling, and N. M. Thiery,
+        .. [HST09] \F. Hivert, A. Schilling, and N. M. Thiéry,
            *Hecke group algebras as quotients of affine Hecke
            algebras at level 0*, JCT A, Vol. 116, (2009) p. 844-863
            :arxiv:`0804.3781`
         """
         a = self.a()
         acheck = self.acheck()
-        if set([1/ZZ(2), 2]).issubset( set(a[i]/acheck[i] for i in self.index_set()) ):
+        s = set(a[i] / acheck[i] for i in self.index_set())
+        if ~ZZ(2) in s and 2 in s:
             # The test above and the formula below are rather meaningless
             # But they detect properly type BC or dual and return the correct value
-            return Family(dict((i, min(ZZ(1), a[i] / acheck[i]))
-                               for i in self.index_set()))
+            return Family({i: min(ZZ.one(), a[i] / acheck[i])
+                           for i in self.index_set()})
 
-        else:
-            return self.c()
+        return self.c()
 
     def _test_dual_classical(self, **options):
         r"""

src/sage/combinat/root_system/type_folded.py

@@ -292,9 +292,9 @@ def f(i):
                 return root.leading_coefficient() / coroot.leading_coefficient()
             index_set = self._cartan_type.index_set()
             min_f = min(f(j) for j in index_set)
-            return Family(dict( (i, int(f(i) / min_f)) for i in index_set ))
+            return Family({i: int(f(i) / min_f) for i in index_set})
         elif self._cartan_type.is_affine():
             c = self._cartan_type.translation_factors()
             cmax = max(c)
-            return Family(dict( (i, int(cmax / c[i]))
-                                for i in self._cartan_type.index_set() ))
+            return Family({i: int(cmax / c[i])
+                           for i in self._cartan_type.index_set()})

src/sage/combinat/root_system/type_reducible.py

@@ -116,11 +116,12 @@ def __init__(self, types):
         """
         self._types = types
         self.affine = False
-        indices = (None,) + tuple( (i, j)
-                                   for i in range(len(types))
-                                   for j in types[i].index_set() )
+        indices = (None,) + tuple((i, j)
+                                  for i in range(len(types))
+                                  for j in types[i].index_set())
         self._indices = indices
-        self._index_relabelling = dict((indices[i], i) for i in range(1, len(indices)))
+        self._index_relabelling = {indices[i]: i
+                                   for i in range(1, len(indices))}
 
         self._spaces = [t.root_system().ambient_space() for t in types]
         if all(l is not None for l in self._spaces):
@@ -130,9 +131,9 @@ def __init__(self, types):
         self.tools = root_system.type_reducible
         # a direct product of finite Cartan types is again finite;
         # idem for simply laced and crystallographic.
-        super_classes = tuple( cls
-                               for cls in (CartanType_finite, CartanType_simply_laced, CartanType_crystallographic)
-                               if all(isinstance(t, cls) for t in types) )
+        super_classes = tuple(cls
+                              for cls in (CartanType_finite, CartanType_simply_laced, CartanType_crystallographic)
+                              if all(isinstance(t, cls) for t in types))
         self._add_abstract_superclass(super_classes)
 
     def _repr_(self, compact=True):  # We should make a consistent choice here

src/sage/combinat/root_system/weight_lattice_realizations.py

@@ -596,10 +596,10 @@ def dynkin_diagram_automorphism_of_alcove_morphism(self, f):
             # Now, we have d = f w^-1
             winv = ~w
             assert all(alpha[i].level().is_zero() for i in self.index_set())
-            rank_simple_roots = dict( (alpha[i],i) for i in self.index_set())
+            rank_simple_roots = {alpha[i]: i for i in self.index_set()}
             permutation = dict()
             for i in self.index_set():
-                root = f(winv.action(alpha[i])) # This is d(alpha_i)
+                root = f(winv.action(alpha[i]))  # This is d(alpha_i)
                 assert root in rank_simple_roots
                 permutation[i] = rank_simple_roots[root]
                 assert set(permutation.values()), set(self.index_set())
@@ -694,7 +694,8 @@ def _test_reduced_word_of_translation(self, elements=None, **options):
             # preserving the alcoves.
             if elements is None:
                 c = self.cartan_type().c()
-                elements = [ c[i] * Lambda[i] for i in self.cartan_type().classical().index_set() ]
+                elements = [c[i] * Lambda[i]
+                            for i in self.cartan_type().classical().index_set()]
 
             # When the null root is zero in this root lattice realization,
             # the roots correspond to the classical roots. We use that to
@@ -703,7 +704,7 @@ def _test_reduced_word_of_translation(self, elements=None, **options):
             # set to be of the form 0..n
             test_automorphism = self.null_root().is_zero() and set(self.index_set()) == set(i for i in range(len(self.index_set())))
             # dictionary assigning a simple root to its index
-            rank_simple_roots = dict( (alpha[i],i) for i in self.index_set() )
+            rank_simple_roots = {alpha[i]: i for i in self.index_set()}
 
             try:
                 W = self.weyl_group()

src/sage/combinat/similarity_class_type.py

@@ -919,11 +919,11 @@ def number_of_classes(self, invertible=False, q=None):
         maximum_degree = max(list_of_degrees)
         numerator = prod([prod([primitives(d+1, invertible=invertible, q=q)-i for i in range(list_of_degrees.count(d+1))]) for d in range(maximum_degree)])
         tau_list = list(self)
-        D = dict((i, tau_list.count(i)) for i in tau_list)
+        D = {i: tau_list.count(i) for i in tau_list}
         denominator = prod(factorial(D[primary_type]) for primary_type in D)
         return numerator / denominator
 
-    def is_semisimple(self):
+    def is_semisimple(self) -> bool:
         """
         Return ``True`` if every primary similarity class type in ``self`` has
         all parts equal to ``1``.
@@ -939,7 +939,7 @@ def is_semisimple(self):
         """
         return all(PT.partition().get_part(0) == 1 for PT in self)
 
-    def is_regular(self):
+    def is_regular(self) -> bool:
         """
         Return ``True`` if every primary type in ``self`` has partition with one
         part.
@@ -1325,8 +1325,9 @@ def dictionary_from_generator(gen):
         high.
     """
     L = list(gen)
-    setofkeys = list(set(item[0] for item in L))
-    return dict((key, sum(entry[1] for entry in (pair for pair in L if pair[0] == key))) for key in setofkeys)
+    setofkeys = set(item[0] for item in L)
+    return {key: sum(pair[1] for pair in L if pair[0] == key)
+            for key in setofkeys}
 
 
 def matrix_similarity_classes(n, q=None, invertible=False):

src/sage/combinat/symmetric_group_algebra.py

@@ -2887,7 +2887,7 @@ def a(tableau, star=0, base_ring=QQ):
     if n <= 1:
         return sgalg.one()
 
-    rd = dict((P(h), one) for h in rs)
+    rd = {P(h): one for h in rs}
     return sgalg._from_dict(rd)
 
 
@@ -2971,7 +2971,7 @@ def b(tableau, star=0, base_ring=QQ):
     if n <= 1:
         return sgalg.one()
 
-    cd = dict((P(v), v.sign() * one) for v in cs)
+    cd = {P(v): v.sign() * one for v in cs}
     return sgalg._from_dict(cd)
 
 

src/sage/crypto/mq/sr.py

@@ -462,7 +462,7 @@ def __init__(self, n=1, r=1, c=1, e=4, star=False, **kwargs):
         self._reverse_variables = bool(kwargs.get("reverse_variables", True))
 
         with AllowZeroInversionsContext(self):
-            sub_byte_lookup = dict([(v, self.sub_byte(v)) for v in self._base])
+            sub_byte_lookup = {v: self.sub_byte(v) for v in self._base}
         self._sub_byte_lookup = sub_byte_lookup
 
         if self._gf2:

src/sage/manifolds/utilities.py

@@ -972,12 +972,10 @@ def _repr_(self):
                     strv[i] = "(" + sv + ")"
 
             # dictionary to group multiple occurrences of differentiation: d/dxdx -> d/dx^2 etc.
-            occ = dict((i, strv[i] + "^" + str(diffargs.count(i))
-                       if (diffargs.count(i) > 1) else strv[i])
-                       for i in diffargs)
+            occ = {i: strv[i] + "^" + str(D) if (D := diffargs.count(i)) > 1
+                   else strv[i] for i in diffargs}
 
-            res = "d" + str(numargs) + "(" + str(funcname) + ")/d" + "d".join(
-                occ.values())
+            res = f"d{numargs}({funcname})/d" + "d".join(occ.values())
 
             # str representation of the operator
             s = self._parent._repr_element_(m[0])