Add idf.copy and idf.deepcopy methods and tests

Implements #118

eppy/modeleditor.py

@@ -977,6 +977,37 @@ def savecopy(self, filename, lineendings='default', encoding='latin-1'):
         """
         self.save(filename, lineendings, encoding)
 
+    def shallowcopy(self):
+        """Make a shallow copy of the IDF.
+
+        This will remain connected to the original IDF, so that changes made to
+        either of the IDFs will be reflected in the other one.
+
+        Returns
+        --------
+        IDF object
+
+        """
+        return copy.copy(self)
+
+    def deepcopy(self):
+        """Make a deep copy of the IDF.
+
+        This will not remain connected to the original IDF, and so changes made
+        to the two IDFs will be independent of each other.
+
+        Returns
+        --------
+        IDF object
+
+        """
+        try:
+            return copy.deepcopy(self)  # this will fail on Python 3
+        except ValueError:
+            newidf = IDF()
+            newidf.initreadtxt(self.idfstr())
+            return newidf
+
     def getiddgroupdict(self):
         """Return a idd group dictionary
         sample: {'Plant-Condenser Loops': ['PlantLoop', 'CondenserLoop'],

eppy/tests/test_modeleditor.py

@@ -428,6 +428,60 @@ def test_savecopy():
     assert idf.idfname == 'test.idf'
 
 
+def test_shallowcopy():
+    """Test that copies made of the IDF using idf.copy remain linked.
+    
+    Fails if changes to a copy are not reflected in the original, and vice
+    versa.
+    
+    """
+    idf_txt = "Building, The White House, , , , , , , ;"    
+    idf1 = IDF()
+    idf1.initreadtxt(idf_txt)
+
+    # make a shallow copy that should remain "entangled" with idf1
+    idf2 = idf1.shallowcopy()
+
+    # change building name in idf1 and check in idf2
+    obj = idf1.getobject('BUILDING', 'The White House')
+    obj.Name = 'Big Ben'
+    assert idf2.getobject('BUILDING', 'Big Ben')
+    assert idf1.idfstr() == idf2.idfstr()  # the two IDFs are the same
+
+    # change building name in idf2 and check in idf1
+    obj = idf2.getobject('BUILDING', 'Big Ben') 
+    obj.Name = 'The Colosseum'
+    assert idf1.getobject('BUILDING', 'The Colosseum')
+    assert idf1.idfstr() == idf2.idfstr()  # the two IDFs are the same
+
+
+def test_deepcopy():
+    """Test that copies made of the IDF using idf.deepcopy do not remain linked.
+    
+    Fails if changes to a copy are reflected in the original, and vice
+    versa.
+    
+    """
+    idf_txt = "Building, The White House, , , , , , , ;"    
+    idf1 = IDF()
+    idf1.initreadtxt(idf_txt)
+
+    # make a deep copy that is not linked to the original IDF
+    idf2 = idf1.deepcopy()
+
+    # change building name in idf1 and check in idf2
+    obj = idf1.getobject('BUILDING', 'The White House')
+    obj.Name = 'Big Ben'
+    assert idf2.getobject('BUILDING', 'The White House')  # unchanged
+    assert idf1.idfstr() != idf2.idfstr()  # the two IDFs are not the same
+
+    # change building name in idf2 and check in idf1
+    obj = idf2.getobject('BUILDING', 'The White House')
+    obj.Name = 'The Colosseum'
+    assert not idf1.getobject('BUILDING', 'The Colosseum')
+    assert idf1.idfstr() != idf2.idfstr()  # the two IDFs are not the same
+
+
 def test_initread():
     """Test for IDF.initread() with filename in unicode and as python str.
     """