variables.Combine now creates a range attribute if all its variables …

…have range.

lena/variables/variable.py

@@ -193,10 +193,14 @@ def __init__(self, *args, **kwargs):
 
         *dim* is the number of variables.
 
+        *range*. If all variables have an attribute *range*,
+        the *range* of this variable is set to a list of them.
+
         All *args* must be *Variables*
         and there must be at least one of them,
         otherwise :class:`LenaTypeError` is raised.
         """
+        # set _vars, dim and getter.
         if not args:
             raise lena.core.LenaTypeError(
                 "Combine must be initialized with 1 or more variables"
@@ -211,6 +215,7 @@ def __init__(self, *args, **kwargs):
         self.dim = len(args)
         getter = lambda val: tuple(var.getter(val) for var in self._vars)
 
+        # update var_context with name and kwargs.
         name = kwargs.pop("name", None)
         if name is None:
             name = "_".join([var.name for var in self._vars])
@@ -221,6 +226,12 @@ def __init__(self, *args, **kwargs):
         var_context["combine"] = tuple(
             copy.deepcopy(var.var_context) for var in self._vars
         )
+
+        # set range of the combined variables
+        if all(hasattr(var, "range") for var in self._vars):
+            range_ = [var.range for var in self._vars]
+            var_context["range"] = range_
+
         super(Combine, self).__init__(name=name, getter=getter, **var_context)
 
     def __getitem__(self, index):

tests/variables/test_variable.py

@@ -19,14 +19,28 @@ def test_combine():
         Combine("xy")
     with pytest.raises(LenaTypeError):
         Combine(lambda x: x)
-    mm = Variable("mm", unit="mm", getter=lambda x: x*10, type="coordinate")
+    mm = Variable("mm", unit="mm", getter=lambda x: x*10, type="coordinate", range=[0, 100])
     c = Combine(mm, name="xy")
     assert c[0] == mm
 
+    # range creation works
+    assert c.range == [mm.range]
+    cm = Variable("cm", unit="cm", getter=lambda x: x, type="coordinate", range=[0, 10])
+    c2 = Combine(mm, cm)
+    assert c2.range == [mm.range, cm.range]
+    # same explicitly
+    assert c2.range == [[0, 100], [0, 10]]
+    # has no range
+    eV = Variable("cm", unit="cm", getter=lambda x: x, type="coordinate")
+    c3 = Combine(mm, eV)
+    with pytest.raises(lena.core.LenaAttributeError):
+        c3.range
+
     ## __call__ works
     data = [1, 2, 3]
     results = map(c, data)
     assert [res[0] for res in results]  == [(10,), (20,), (30,)]
+    mm = Variable("mm", unit="mm", getter=lambda x: x*10, type="coordinate")
     m = Variable("m", unit="m", getter=lambda x: x/100., type="coordinate")
     c = Combine(mm, m)
     results = map(c, data)