Copy Attributes when copy is used.

nbodykit/base/catalog.py

@@ -471,6 +471,10 @@ def copy(self):
         .. note::
             No copy of data is made.
 
+        .. note::
+            This is different from view in that the attributes dictionary
+            of the copy no longer related to ``self``.
+
         Returns
         -------
         CatalogSource :
@@ -488,6 +492,10 @@ def copy(self):
         for col in self.columns:
             toret[col] = self[col]
 
+        # copy the attributes too, so they become decoupled
+        # this is different from view.
+        toret._attrs = self._attrs.copy()
+
         return toret
 
     def get_hardcolumn(self, col):

nbodykit/base/tests/test_catalog.py

@@ -288,6 +288,14 @@ def test_copy(comm):
     for k in source.attrs:
         assert k in copy.attrs
 
+    # adding columns to the copy doesn't add to original source
+    copy['TEST2'] = 5.0
+    assert 'TEST2' not in source
+
+    # make sure attrs are independent.
+    source.attrs['foo'] = 123
+    assert 'foo' not in copy.attrs
+
 @MPITest([4])
 def test_view(comm):
     CurrentMPIComm.set(comm)
@@ -309,3 +317,7 @@ def test_view(comm):
     # adding columns to the view changes original source
     view['TEST2'] = 5.0
     assert 'TEST2' in source
+
+    # make sure attrs are dependent.
+    source.attrs['foo'] = 123
+    assert 'foo' in view.attrs