Add docu and cosmetics

nifty5/operators/domain_distributor.py

@@ -28,11 +28,26 @@ from .linear_operator import LinearOperator
 
 
 class DomainDistributor(LinearOperator):
+    """A linear operator which broadcasts a field to a larger domain.
+
+    This DomainDistributor broadcasts a field which is defined on a
+    DomainTuple to a DomainTuple which contains the former as a subset. The
+    entries of the field are copied such that they are constant in the
+    direction of the new spaces.
+
+    Parameters
+    ----------
+    target : Domain, tuple of Domain or DomainTuple
+    spaces : int or tuple of int
+        The elements of "target" which are taken as domain.
+    """
+
     def __init__(self, target, spaces):
         self._target = DomainTuple.make(target)
         self._spaces = utilities.parse_spaces(spaces, len(self._target))
-        self._domain = [tgt for i, tgt in enumerate(self._target)
-                        if i in self._spaces]
+        self._domain = [
+            tgt for i, tgt in enumerate(self._target) if i in self._spaces
+        ]
         self._domain = DomainTuple.make(self._domain)
         self._capability = self.TIMES | self.ADJOINT_TIMES
 
@@ -43,9 +58,9 @@ class DomainDistributor(LinearOperator):
             shp = []
             for i, tgt in enumerate(self._target):
                 tmp = tgt.shape if i > 0 else tgt.local_shape
-                shp += tmp if i in self._spaces else(1,)*len(tgt.shape)
+                shp += tmp if i in self._spaces else (1,)*len(tgt.shape)
             ldat = np.broadcast_to(ldat.reshape(shp), self._target.local_shape)
             return Field.from_local_data(self._target, ldat)
         else:
-            return x.sum([s for s in range(len(x.domain))
-                          if s not in self._spaces])
+            return x.sum(
+                [s for s in range(len(x.domain)) if s not in self._spaces])