gh-38666: some care for pep8 E203 in pyx files
    
fixing all E203 warnings in pyx files (except 2 files)

``` E203 whitespace before```

### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
    
URL: #38666
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert

Author: Release Manager

src/sage/algebras/fusion_rings/fast_parallel_fmats_methods.pyx

@@ -399,7 +399,7 @@ cdef list compute_gb(factory, tuple args):
     cdef MPolynomialRing_libsingular R = PolynomialRing(factory._FR.field(), len(sorted_vars), 'a', order=term_order)
 
     # Zip tuples into R and compute Groebner basis
-    cdef idx_map = {old : new for new, old in enumerate(sorted_vars)}
+    cdef idx_map = {old: new for new, old in enumerate(sorted_vars)}
     nvars = len(sorted_vars)
     F = factory.field()
     cdef list polys = list()

src/sage/coding/codecan/codecan.pyx

@@ -916,8 +916,8 @@ cdef class PartitionRefinementLinearCode(PartitionRefinement_generic):
         if self._inner_group.rank < 2:
             return True
 
-        lower = iter(self._matrix[ : self._inner_group.rank].columns())
-        upper = iter(self._matrix[self._inner_group.rank : ].columns())
+        lower = iter(self._matrix[:self._inner_group.rank].columns())
+        upper = iter(self._matrix[self._inner_group.rank:].columns())
 
         for i in range(self._n):
             l = next(lower)

src/sage/combinat/designs/designs_pyx.pyx

@@ -289,14 +289,14 @@ def is_orthogonal_array(OA, int k, int n, int t=2, verbose=False, terminology='O
     for R in OA:
         if len(R) != k:
             if verbose:
-                print({"OA"   : "Some row does not have length "+str(k),
-                       "MOLS" : "The number of squares is not "+str(k-2)}[terminology])
+                print({"OA": "Some row does not have length "+str(k),
+                       "MOLS": "The number of squares is not "+str(k-2)}[terminology])
             return False
 
     if len(OA) != n2:
         if verbose:
-            print({"OA"   : "The number of rows is {} instead of {}^2={}".format(len(OA),n,n2),
-                   "MOLS" : "All squares do not have dimension n^2={}^2".format(n)}[terminology])
+            print({"OA": "The number of rows is {} instead of {}^2={}".format(len(OA),n,n2),
+                   "MOLS": "All squares do not have dimension n^2={}^2".format(n)}[terminology])
         return False
 
     if n == 0:
@@ -319,8 +319,8 @@ def is_orthogonal_array(OA, int k, int n, int t=2, verbose=False, terminology='O
         for j,x in enumerate(R):
             if x < 0 or x >= n:
                 if verbose:
-                    print({"OA"   : "{} is not in the interval [0..{}]".format(x,n-1),
-                           "MOLS" : "Entry {} was expected to be in the interval [0..{}]".format(x,n-1)}[terminology])
+                    print({"OA": "{} is not in the interval [0..{}]".format(x,n-1),
+                           "MOLS": "Entry {} was expected to be in the interval [0..{}]".format(x,n-1)}[terminology])
                 sig_free(OAc)
                 return False
             OAc[j*n2+i] = x
@@ -341,8 +341,8 @@ def is_orthogonal_array(OA, int k, int n, int t=2, verbose=False, terminology='O
                 sig_free(OAc)
                 bitset_free(seen)
                 if verbose:
-                    print({"OA"   : "Columns {} and {} are not orthogonal".format(i,j),
-                           "MOLS" : "Squares {} and {} are not orthogonal".format(i,j)}[terminology])
+                    print({"OA": "Columns {} and {} are not orthogonal".format(i,j),
+                           "MOLS": "Squares {} and {} are not orthogonal".format(i,j)}[terminology])
                 return False
 
     sig_free(OAc)

src/sage/combinat/designs/orthogonal_arrays_find_recursive.pyx

@@ -145,7 +145,7 @@ cpdef find_product_decomposition(int k,int n):
         sage: _ = f(*args)
     """
     cdef int n1,n2
-    for n1 in range(2,n):
+    for n1 in range(2, n):
         n2 = n/n1  # n2 is decreasing along the loop
         if n2 < n1:
             break
@@ -194,15 +194,13 @@ cpdef find_wilson_decomposition_with_one_truncated_group(int k,int n):
         if u == 0 or (u>1 and k >= u+2):
             continue
 
-        m = n/r
+        m = n // r
         # If there exists a TD(k,m) then k<m+2
         if k >= m+2:
             break
 
-        if (is_available(k  ,m  ) and
-            is_available(k  ,m+1) and
-            is_available(k+1,r  ) and
-            is_available(k  ,u  )):
+        if (is_available(k, m) and is_available(k, m + 1) and
+            is_available(k + 1, r) and is_available(k, u)):
             from sage.combinat.designs.orthogonal_arrays import wilson_construction
             return wilson_construction, (None,k,r,m,(u,),False)
 
@@ -294,22 +292,20 @@ cpdef find_construction_3_3(int k,int n):
         sage: find_construction_3_3(12,11)
     """
     cdef int mm,nn,i
-    for mm in range(k-1,n/2+1):
-        if (not is_available(k ,mm  ) or
-            not is_available(k ,mm+1)):
+    for mm in range(k-1, n//2+1):
+        if not(is_available(k, mm) and is_available(k, mm + 1)):
             continue
 
-        for nn in range(2,n/mm+1):
+        for nn in range(2, n//mm+1):
             i = n-nn*mm
-            if i<=0:
+            if i <= 0:
                 continue
 
-            if (is_available(k+i, nn  ) and
-                is_available(k  , mm+i)):
+            if is_available(k + i, nn) and is_available(k, mm + i):
                 from sage.combinat.designs.orthogonal_arrays_build_recursive import construction_3_3
-                return construction_3_3, (k,nn,mm,i)
+                return construction_3_3, (k, nn, mm, i)
 
-cpdef find_construction_3_4(int k,int n):
+cpdef find_construction_3_4(int k, int n):
     r"""
     Find a decomposition for construction 3.4 from [AC07]_.
 
@@ -339,20 +335,20 @@ cpdef find_construction_3_4(int k,int n):
             not is_available(k,mm+2)):
             continue
 
-        for nn in range(2,n/mm+1):
+        for nn in range(2, n//mm+1):
             i = n-nn*mm
             if i<=0:
                 continue
 
             for s in range(1,min(i,nn)):
                 r = i-s
-                if (is_available(k+r+1,nn) and
-                    is_available(k    , s) and
-                    (is_available(k,mm+r) or is_available(k,mm+r+1))):
+                if (is_available(k + r + 1, nn) and
+                    is_available(k, s) and
+                    (is_available(k, mm + r) or is_available(k, mm + r + 1))):
                     from sage.combinat.designs.orthogonal_arrays_build_recursive import construction_3_4
-                    return construction_3_4, (k,nn,mm,r,s)
+                    return construction_3_4, (k, nn, mm, r, s)
 
-cpdef find_construction_3_5(int k,int n):
+cpdef find_construction_3_5(int k, int n):
     r"""
     Find a decomposition for construction 3.5 from [AC07]_.
 
@@ -376,14 +372,14 @@ cpdef find_construction_3_5(int k,int n):
         sage: find_construction_3_5(9,24)
     """
     cdef int mm,i,nn,r,s,t
-    for mm in range(2,n/2+1):
+    for mm in range(2, n//2+1):
         if (mm+3 >= n or
             not is_available(k,mm+1) or
             not is_available(k,mm+2) or
             not is_available(k,mm+3)):
             continue
 
-        for nn in range(2,n/mm+1):
+        for nn in range(2, n//mm+1):
             i = n-nn*mm
             if i<=0:
                 continue
@@ -433,7 +429,7 @@ cpdef find_construction_3_6(int k,int n):
             not is_available(k,mm+2)):
             continue
 
-        for nn in range(2,n/mm+1):
+        for nn in range(2, n//mm+1):
             i = n-nn*mm
             if i<=0:
                 continue
@@ -913,7 +909,7 @@ cpdef find_brouwer_van_rees_with_one_truncated_column(int k,int n):
     cdef tuple values
 
     # We write n=rm+remainder
-    for m in range(2,n//2):
+    for m in range(2, n//2):
         if not is_available(k,m):
             continue
 
@@ -935,7 +931,7 @@ cpdef find_brouwer_van_rees_with_one_truncated_column(int k,int n):
             continue
 
         max_multiplier = max(available_multipliers)
-        for r in range(2,n//m+1):
+        for r in range(2, n//m+1):
             remainder = n-r*m
             if (remainder > r*max_multiplier or
                 not is_available(k+1,r) or

src/sage/libs/flint/fmpz_poly_sage.pyx

@@ -87,9 +87,9 @@ cdef class Fmpz_poly(SageObject):
             sage: f[2] == 10**100000
             True
         """
-        if isinstance(value, Integer) :
+        if isinstance(value, Integer):
             fmpz_poly_set_coeff_mpz(self.poly, i, (<Integer>value).value)
-        else :
+        else:
             fmpz_poly_set_coeff_si(self.poly, i, value)
 
     def __getitem__(self, i):
@@ -336,7 +336,7 @@ cdef class Fmpz_poly(SageObject):
         fmpz_poly_divrem(Q.poly, R.poly, self.poly, other.poly)
         return Q, R
 
-    def left_shift(self, unsigned long n) :
+    def left_shift(self, unsigned long n):
         """
         Left shift ``self`` by `n`.
 
@@ -353,7 +353,7 @@ cdef class Fmpz_poly(SageObject):
 
         return res
 
-    def right_shift(self, unsigned long n) :
+    def right_shift(self, unsigned long n):
         """
         Right shift ``self`` by `n`.
 
@@ -383,7 +383,7 @@ cdef class Fmpz_poly(SageObject):
         fmpz_poly_pseudo_divrem(Q.poly, R.poly, &d, self.poly, other.poly)
         return Q, R, d
 
-    def derivative(self) :
+    def derivative(self):
         """
         Return the derivative of ``self``.