Manual backport of PR 14357 onto v5.0.x (Fix bug creating QTable with units arg set)

astropy/table/table.py

@@ -922,7 +922,12 @@ def _set_column_attribute(self, attr, values):
                     value = None
 
             if value not in (np.ma.masked, None):
-                setattr(self[name].info, attr, value)
+                col = self[name]
+                if attr == "unit" and isinstance(col, Quantity):
+                    # Update the Quantity unit in-place
+                    col <<= value
+                else:
+                    setattr(col.info, attr, value)
 
     def __getstate__(self):
         columns = OrderedDict(

astropy/table/tests/test_init_table.py

@@ -6,8 +6,8 @@
 import pytest
 import numpy as np
 
-from astropy.table import Column, TableColumns, Table, MaskedColumn
 import astropy.units as u
+from astropy.table import Column, MaskedColumn, QTable, Table, TableColumns
 
 
 class DictLike(Mapping):
@@ -619,3 +619,16 @@ def test_init_Table_from_list_of_quantity():
     assert np.all(t["x"] == [5, 10])
     assert t["y"][0] == 1 * u.m
     assert t["y"][1] == 3
+
+
+def test_init_QTable_and_set_units():
+    """
+    Test fix for #14336 where providing units to QTable init fails.
+
+    This applies when the input is a Quantity.
+    """
+    t = QTable([[1, 2] * u.km, [1, 2]], units={"col0": u.m, "col1": u.s})
+    assert t["col0"].unit == u.m
+    assert np.all(t["col0"].value == [1000, 2000])
+    assert t["col1"].unit == u.s
+    assert np.all(t["col1"].value == [1, 2])

docs/changes/table/14357.bugfix.rst

@@ -0,0 +1,3 @@
+Fix a bug when creating a ``QTable`` when a ``Quantity`` input column is present and the
+``units`` argument modifies the unit of that column. This now works as expected where
+previously this caused an exception.