Preserve column order in YAML export

yaml.safe_dump sorts mapping keys alphabetically by default, so YAML export
reordered columns (e.g. apple, id, name, zebra) inconsistently with the CSV and
JSON exports, which keep the dataset's header order.

Pass sort_keys=False when dumping the dataset and databook so YAML keeps the
original column order.

Fixes #287

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: vineethsaivs

src/tablib/formats/_yaml.py

@@ -14,14 +14,20 @@ class YAMLFormat:
     def export_set(cls, dataset):
         """Returns YAML representation of Dataset."""
         return yaml.safe_dump(
-            dataset._package(), default_flow_style=None, allow_unicode=True
+            dataset._package(),
+            default_flow_style=None,
+            allow_unicode=True,
+            sort_keys=False,
         )
 
     @classmethod
     def export_book(cls, databook):
         """Returns YAML representation of Databook."""
         return yaml.safe_dump(
-            databook._package(), default_flow_style=None, allow_unicode=True
+            databook._package(),
+            default_flow_style=None,
+            allow_unicode=True,
+            sort_keys=False,
         )
 
     @classmethod

tests/test_tablib.py

@@ -1709,14 +1709,22 @@ def test_yaml_export(self):
 
         self.founders.append(('名字', '李', 60))
         expected = """\
-- {first_name: John, gpa: 90, last_name: Adams}
-- {first_name: George, gpa: 67, last_name: Washington}
-- {first_name: Thomas, gpa: 50, last_name: Jefferson}
-- {first_name: 名字, gpa: 60, last_name: 李}
+- {first_name: John, last_name: Adams, gpa: 90}
+- {first_name: George, last_name: Washington, gpa: 67}
+- {first_name: Thomas, last_name: Jefferson, gpa: 50}
+- {first_name: 名字, last_name: 李, gpa: 60}
 """
         output = self.founders.yaml
         self.assertEqual(output, expected)
 
+    def test_yaml_export_preserves_column_order(self):
+        """YAML export must keep the dataset's column order instead of sorting the keys
+        alphabetically."""
+        data = tablib.Dataset()
+        data.headers = ('name', 'id', 'zebra', 'apple')
+        data.append(('x', 1, 'z', 'a'))
+        self.assertEqual(data.yaml.strip(), '- {name: x, id: 1, zebra: z, apple: a}')
+
     def test_yaml_load(self):
         """ test issue 524: invalid format  """
         yaml_source = Path(__file__).parent / 'files' / 'issue_524.yaml'