RangeSet: allow slice object in fromone()

lib/ClusterShell/RangeSet.py

@@ -185,9 +185,16 @@ def fromlist(cls, rnglist, autostep=None):
 
     @classmethod
     def fromone(cls, index, pad=0, autostep=None):
-        """Class method that returns a new RangeSet of one single item."""
+        """Class method that returns a new RangeSet of one single item or
+        a single range (from integer or slice object)."""
         inst = RangeSet(autostep=autostep)
-        inst.add(index, pad)
+        # support slice object with duck-typing
+        try:
+            inst.add(index, pad)
+        except TypeError:
+            if not index.stop:
+                raise ValueError("Invalid range upper limit (%s)" % index.stop)
+            inst.add_range(index.start or 0, index.stop, index.step or 1, pad)
         return inst
 
     def get_autostep(self):

tests/RangeSetTest.py

@@ -691,6 +691,22 @@ def testFromOneConstructor(self):
         rgs = RangeSet.fromone(42)
         self.assertEqual(str(rgs), "42")
         self.assertEqual(len(rgs), 1)
+        # also support slice object (v1.6+)
+        rgs = RangeSet.fromone(slice(42))
+        self.assertEqual(str(rgs), "0-41")
+        self.assertEqual(len(rgs), 42)
+        self.assertRaises(ValueError, RangeSet.fromone, slice(12, None))
+        rgs = RangeSet.fromone(slice(42, 43))
+        self.assertEqual(str(rgs), "42")
+        self.assertEqual(len(rgs), 1)
+        rgs = RangeSet.fromone(slice(42, 48))
+        self.assertEqual(str(rgs), "42-47")
+        self.assertEqual(len(rgs), 6)
+        rgs = RangeSet.fromone(slice(42, 57, 2))
+        self.assertEqual(str(rgs), "42,44,46,48,50,52,54,56")
+        rgs.autostep = 3
+        self.assertEqual(str(rgs), "42-56/2")
+        self.assertEqual(len(rgs), 8)
 
     def testIterator(self):
         """test RangeSet iterator"""