Merge pull request #4930 from taldcroft/tablepkey

Make Table inherit primary_key attribute from its parent Table.

CHANGES.rst

@@ -1423,6 +1423,9 @@ New Features
 
 - ``astropy.table``
 
+  - Fixed bug where Tables created from existing Table objects were not
+    inheriting the ``primary_key`` attribute. [#4672]
+
 - ``astropy.time``
 
 - ``astropy.units``

astropy/table/table.py

@@ -675,6 +675,7 @@ def _init_from_table(self, data, names, dtype, n_cols, copy):
         table = data  # data is really a Table, rename for clarity
         self.meta.clear()
         self.meta.update(deepcopy(table.meta))
+        self.primary_key = table.primary_key
         cols = list(table.columns.values())
 
         self._init_from_list(cols, names, dtype, n_cols, copy)
@@ -714,6 +715,7 @@ def _new_from_slice(self, slice_):
         table = self.__class__(masked=self.masked)
         table.meta.clear()
         table.meta.update(deepcopy(self.meta))
+        table.primary_key = self.primary_key
         cols = self.columns.values()
 
         newcols = []

astropy/table/tests/test_table.py

@@ -1711,3 +1711,28 @@ def test_replace_column_qtable():
     assert t.colnames == ['a', 'b']
     assert t['a'].info.meta is None
     assert t['a'].info.format is None
+
+def test_primary_key_is_inherited():
+    """Test whether a new Table inherits the primary_key attribute from
+    its parent Table. Issue #4672"""
+
+    t = table.Table([(2, 3, 2, 1), (8, 7, 6, 5)], names=('a', 'b'))
+    t.add_index('a')
+    original_key = t.primary_key
+
+    # can't test if tuples are equal, so just check content
+    assert original_key[0] is 'a'
+
+    t2 = t[:]
+    t3 = t.copy()
+    t4 = table.Table(t)
+
+    # test whether the reference is the same in the following
+    assert original_key == t2.primary_key
+    assert original_key == t3.primary_key
+    assert original_key == t4.primary_key
+
+    # just test one element, assume rest are equal if assert passes
+    assert t.loc[1] == t2.loc[1]
+    assert t.loc[1] == t3.loc[1]
+    assert t.loc[1] == t4.loc[1]