more cleanups

nifty5/operators/operator.py

@@ -196,7 +196,8 @@ class _ConstCollector(object):
             self._nc |= set(fulldom.keys()) - set(const.keys())
             if self._const is None:
                 self._const = MultiField.from_dict(
-                    {key: const[key] for key in const.keys() if key not in self._nc})
+                    {key: const[key]
+                     for key in const.keys() if key not in self._nc})
             else:
                 self._const = self._const.unite(const)
                 self._const = MultiField.from_dict(

nifty5/operators/simple_linear_operators.py

@@ -296,15 +296,13 @@ class _PartialExtractor(LinearOperator):
             raise TypeError("MultiDomain expected")
         self._domain = domain
         self._target = target
+        for key in self._target.keys():
+            if not (self._domain[key] is not self._target[key]):
+                raise ValueError("domain mismatch")
         self._capability = self.TIMES | self.ADJOINT_TIMES
 
     def apply(self, x, mode):
         self._check_input(x, mode)
         if mode == self.TIMES:
-            res = x.extract(self._target)
-            assert res.domain is self.target
-            return res
-        fld = {key: x[key] if key in x.domain.keys() else Field.full(self._domain[key], 0.)
-               for key in self._domain.keys()}
-        assert MultiField.from_dict(fld).domain is self.domain
-        return MultiField.from_dict(fld)
+            return x.extract(self._target)
+        return MultiField.from_dict({key: x[key] for key in x.domain.keys()})

nifty5/operators/sum_operator.py

@@ -202,8 +202,8 @@ class SumOperator(LinearOperator):
         return "SumOperator:\n"+indent(subs)
 
     def _simplify_for_constant_input_nontrivial(self, c_inp):
-        f=[]
-        o=[]
+        f = []
+        o = []
         for op in self._ops:
             tf, to = op.simplify_for_constant_input(
                 c_inp.extract_part(op.domain))