fix suggested details

Author: fchapoton

src/sage/rings/number_field/homset.py

@@ -143,7 +143,7 @@ def _an_element_(self):
         else:
             from sage.categories.sets_cat import EmptySetError
             raise EmptySetError("There is no morphism from {} to {}".format(
-                                              self.domain(), self.codomain()))
+                self.domain(), self.codomain()))
 
     def _repr_(self):
         r"""
@@ -238,7 +238,7 @@ def list(self):
             v = [D.hom([r], codomain=C, check=False) for r in roots]
         else:
             v = []
-        return Sequence(v, universe=self, check=False, immutable=True, cr=v != [])
+        return Sequence(v, universe=self, check=False, immutable=True, cr=bool(v))
 
     def __getitem__(self, n):
         r"""
@@ -389,7 +389,7 @@ def _element_constructor_(self, x, base_map=None, base_hom=None, check=True):
                 raise ValueError("codomain of absolute homomorphism must be codomain of this homset.")
             return self.element_class(self, x)
         if (isinstance(x, RelativeNumberFieldHomomorphism_from_abs)
-            and x.parent() == self):
+                and x.parent() == self):
             return self.element_class(self, x.abs_hom())
         if base_map is None:
             base_map = self.default_base_hom()
@@ -519,7 +519,7 @@ def list(self):
         C = self.codomain()
         D_abs = D.absolute_field('a')
         v = [self(f, check=False) for f in D_abs.Hom(C).list()]
-        return Sequence(v, universe=self, check=False, immutable=True, cr=v != [])
+        return Sequence(v, universe=self, check=False, immutable=True, cr=bool(v))
 
 
 class CyclotomicFieldHomset(NumberFieldHomset):
@@ -579,7 +579,7 @@ def _element_constructor_(self, x, check=True):
             x^2 + b
         """
         if (isinstance(x, CyclotomicFieldHomomorphism_im_gens)
-            and x.parent() == self):
+                and x.parent() == self):
             return self.element_class(self, x.im_gens())
         return self.element_class(self, x, check=check)
 
@@ -622,4 +622,4 @@ def list(self):
             else:
                 w = C.zeta(n)
             v = [self([w**k], check=False) for k in Zmod(n) if k.is_unit()]
-        return Sequence(v, universe=self, check=False, immutable=True, cr=v != [])
+        return Sequence(v, universe=self, check=False, immutable=True, cr=bool(v))

src/sage/rings/number_field/number_field_rel.py

@@ -463,7 +463,7 @@ def subfields(self, degree=0, name=None):
             if to_K is not None:
                 to_K = RelativeNumberFieldHomomorphism_from_abs(self.Hom(K), to_K*to_abs)
             ans.append((K, from_K, to_K))
-        ans = Sequence(ans, immutable=True, cr=ans != [])
+        ans = Sequence(ans, immutable=True, cr=bool(ans))
         return ans
 
     def is_absolute(self):
@@ -2077,7 +2077,7 @@ def embeddings(self, K):
         # then it is most natural, so we put it first.
         put_natural_embedding_first(v)
 
-        self.__embeddings[K] = Sequence(v, cr=v != [], immutable=True, check=False, universe=self.Hom(K))
+        self.__embeddings[K] = Sequence(v, cr=bool(v), immutable=True, check=False, universe=self.Hom(K))
         return self.__embeddings[K]
 
     def automorphisms(self):
@@ -2152,13 +2152,14 @@ def automorphisms(self):
 
         L = self.absolute_field('a')
         L_into_self, self_into_L = L.structure()
-        aas = L.automorphisms() # absolute automorphisms
+        aas = L.automorphisms()  # absolute automorphisms
 
         a = self_into_L(self.gen())
         abs_base_gens = [self_into_L(_) for _ in self.base_field().gens()]
-        v = sorted([ self.hom([ L_into_self(aa(a)) ]) for aa in aas if all(aa(g) == g for g in abs_base_gens) ])
+        v = sorted([self.hom([L_into_self(aa(a))]) for aa in aas
+                    if all(aa(g) == g for g in abs_base_gens)])
         put_natural_embedding_first(v)
-        self.__automorphisms = Sequence(v, cr=(v != []), immutable=True,
+        self.__automorphisms = Sequence(v, cr=bool(v), immutable=True,
                                         check=False, universe=self.Hom(self))
         return self.__automorphisms