factor out common code

nifty5/operators/linear_operator.py

@@ -259,10 +259,4 @@ class LinearOperator(Operator):
 
     def _check_input(self, x, mode):
         self._check_mode(mode)
-        if self._dom(mode) != x.domain:
-            s = "The operator's and field's domains don't match."
-            from ..domain_tuple import DomainTuple
-            from ..multi_domain import MultiDomain
-            if not isinstance(self._dom(mode), [DomainTuple, MultiDomain]):
-                s += " Your operator's domain is neither a `DomainTuple` nor a `MultiDomain`."
-            raise ValueError(s)
+        self._check_domain_equality(self._dom(mode), x.domain)

nifty5/operators/operator.py

@@ -23,6 +23,17 @@ class Operator(NiftyMetaBase()):
             The domain on which the Operator's output Field lives."""
         return self._target
 
+    @staticmethod
+    def _check_domain_equality(dom_op, dom_field):
+        if dom_op != dom_field:
+            s = "The operator's and field's domains don't match."
+            from ..domain_tuple import DomainTuple
+            from ..multi_domain import MultiDomain
+            if not isinstance(dom_op, [DomainTuple, MultiDomain]):
+                s += " Your operator's domain is neither a `DomainTuple`" \
+                     " nor a `MultiDomain`."
+            raise ValueError(s)
+
     def scale(self, factor):
         if factor == 1:
             return self
@@ -66,13 +77,7 @@ class Operator(NiftyMetaBase()):
     def _check_input(self, x):
         from ..linearization import Linearization
         d = x.target if isinstance(x, Linearization) else x.domain
-        if self._domain != d:
-            s = "The operator's and field's domains don't match."
-            from ..domain_tuple import DomainTuple
-            from ..multi_domain import MultiDomain
-            if not isinstance(self._dom(mode), [DomainTuple, MultiDomain]):
-                s += " Your operator's domain is neither a `DomainTuple` nor a `MultiDomain`."
-            raise ValueError(s)
+        self._check_domain_equality(self._domain, d)
 
     def __call__(self, x):
         if isinstance(x, Operator):