gh-39332: some changes about dict in combinat (ruff PLC0206)
    
some changes for ruff code PLC0206 in the `combinat` folder

This is about using `.items()` when possible

### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
    
URL: #39332
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert

Author: Release Manager

src/sage/combinat/binary_recurrence_sequences.py

@@ -729,8 +729,8 @@ def pthpowers(self, p, Bound):
 
                     # Check how long each element has persisted, if it is for at least 7 cycles,
                     # then we check to see if it is actually a perfect power
-                    for i in Possible_count:
-                        if Possible_count[i] == 7:
+                    for i, pci in Possible_count.items():
+                        if pci == 7:
                             n = Integer(i)
                             if n < Bound:
                                 if _is_p_power(self(n), p):

src/sage/combinat/chas/wqsym.py

@@ -986,12 +986,12 @@ def union(X, Y):
             cur = {data[0]: 1}
             for B in data[1:]:
                 ret = {}
-                for A in cur:
+                for A, curA in cur.items():
                     for C in ShuffleProduct_overlapping(A, B, element_constructor=OSP, add=union):
                         if C in ret:
-                            ret[C] += cur[A]
+                            ret[C] += curA
                         else:
-                            ret[C] = cur[A]
+                            ret[C] = curA
                 cur = ret
 
             # Return the result in the X basis

src/sage/combinat/designs/bibd.py

@@ -1277,14 +1277,14 @@ def BIBD_5q_5_for_q_prime_power(q):
 
     d = (q-1)//4
     B = []
-    F = FiniteField(q,'x')
+    F = FiniteField(q, 'x')
     a = F.primitive_element()
-    L = {b:i for i,b in enumerate(F)}
-    for b in L:
-        B.append([i*q + L[b] for i in range(5)])
+    L = {b: i for i, b in enumerate(F)}
+    for b, Lb in L.items():
+        B.append([i*q + Lb for i in range(5)])
         for i in range(5):
             for j in range(d):
-                B.append([        i*q + L[b          ],
+                B.append([        i*q + Lb,
                           ((i+1) % 5)*q + L[ a**j+b    ],
                           ((i+1) % 5)*q + L[-a**j+b    ],
                           ((i+4) % 5)*q + L[ a**(j+d)+b],

src/sage/combinat/designs/difference_family.py

@@ -292,8 +292,8 @@ def is_difference_family(G, D, v=None, k=None, l=None, verbose=False):
 
         # Normalized number of occurrences added to counter
         stabi = len(stab[i])
-        for gg in tmp_counter:
-            counter[gg] += tmp_counter[gg]//stabi
+        for gg, tmp_gg in tmp_counter.items():
+            counter[gg] += tmp_gg // stabi
 
     # Check the counter and report any error
     too_few = []

src/sage/combinat/parallelogram_polyomino.py

@@ -311,8 +311,7 @@ def __call__(self, *get_values, **options):
             {'diagram': 'diagram representation',
             'list': 'list representation'}}
         """
-        for key in options:
-            value = options[key]
+        for key, value in options.items():
             self.__setitem__(key, value)
         for key in get_values:
             return self.__getitem__(key)

src/sage/combinat/posets/incidence_algebras.py

@@ -456,9 +456,9 @@ def __init__(self, I, prefix='R') -> None:
         for i in self._ambient.basis().keys():
             S = P.subposet(P.interval(*i))
             added = False
-            for k in EC:
+            for k, ECk in EC.items():
                 if S._hasse_diagram.is_isomorphic(k._hasse_diagram):
-                    EC[k].append(i)
+                    ECk.append(i)
                     added = True
                     break
             if not added:

src/sage/combinat/posets/posets.py

@@ -2056,10 +2056,10 @@ def plot(self, label_elements=True, element_labels=None,
                   'cover_colors': 'edge_colors',
                   'cover_style': 'edge_style',
                   'border': 'graph_border'}
-        for param in rename:
+        for param, value in rename.items():
             tmp = kwds.pop(param, None)
             if tmp is not None:
-                kwds[rename[param]] = tmp
+                kwds[value] = tmp
 
         heights = kwds.pop('heights', None)
         if heights is None:

src/sage/combinat/rigged_configurations/kleber_tree.py

@@ -666,8 +666,8 @@ def latex_options(self, **options):
         if not options:
             from copy import copy
             return copy(self._latex_options)
-        for k in options:
-            self._latex_options[k] = options[k]
+        for key, value in options.items():
+            self._latex_options[key] = value
 
     def _latex_(self):
         r"""

src/sage/combinat/root_system/weyl_characters.py

@@ -761,14 +761,9 @@ def _demazure_helper(self, dd, word='long', debug=False):
                         next[mu] = next.get(mu, 0) - accum[v]
                         if debug:
                             print("     mu=%s, next[mu]=%s" % (mu, next[mu]))
-            accum = {}
-            for v in next:
-                accum[v] = next[v]
-        ret = {}
-        for v in accum:
-            if accum[v]:
-                ret[self._space.from_vector_notation(v, style='coroots')] = accum[v]
-        return ret
+            accum = dict(next)
+        return {self._space.from_vector_notation(v, style='coroots'): val
+                for v, val in accum.items() if val}
 
     @cached_method
     def _weight_multiplicities(self, x):

src/sage/combinat/sf/classical.py

@@ -30,7 +30,11 @@
 from . import jack
 from . import orthotriang
 
-translate = {'monomial':'MONOMIAL', 'homogeneous':'HOMSYM', 'powersum':'POWSYM', 'elementary':'ELMSYM', 'Schur':'SCHUR'}
+translate = {'monomial': 'MONOMIAL',
+             'homogeneous': 'HOMSYM',
+             'powersum': 'POWSYM',
+             'elementary': 'ELMSYM',
+             'Schur': 'SCHUR'}
 
 conversion_functions = {}
 
@@ -55,11 +59,11 @@ def init():
         s[1, 1, 1, 1] - s[2, 1, 1] + 2*s[2, 2] - s[3, 1] + s[4]
     """
     import sage.libs.symmetrica.all as symmetrica
-    for other_basis in translate:
-        for basis in translate:
+    for other_basis, other_name in translate.items():
+        for basis, name in translate.items():
             try:
                 conversion_functions[(other_basis, basis)] = getattr(symmetrica,
-                     't_{}_{}'.format(translate[other_basis], translate[basis]))
+                        f't_{other_name}_{name}')
             except AttributeError:
                 pass