cppmule · April 14, 2017 10:16 · Feb 25, 2011
diff --git a/yaml_ordered_dict.py b/yaml_ordered_dict.py
@@ -0,0 +1,65 @@
+import yaml
+import yaml.constructor
+
+try:
+    # included in standard lib from Python 2.7
+    from collections import OrderedDict
+except ImportError:
+    # try importing the backported drop-in replacement
+    # it's available on PyPI
+    from ordereddict import OrderedDict
+
+class OrderedDictYAMLLoader(yaml.Loader):
+    """
+    A YAML loader that loads mappings into ordered dictionaries.
+    """
+
+    def __init__(self, *args, **kwargs):
+        yaml.Loader.__init__(self, *args, **kwargs)
+
+        self.add_constructor(u'tag:yaml.org,2002:map', type(self).construct_yaml_map)
+        self.add_constructor(u'tag:yaml.org,2002:omap', type(self).construct_yaml_map)
+
+    def construct_yaml_map(self, node):
+        data = OrderedDict()
+        yield data
+        value = self.construct_mapping(node)
+        data.update(value)
+
+    def construct_mapping(self, node, deep=False):
+        if isinstance(node, yaml.MappingNode):
+            self.flatten_mapping(node)
+        else:
+            raise yaml.constructor.ConstructorError(None, None,
+                'expected a mapping node, but found %s' % node.id, node.start_mark)
+
+        mapping = OrderedDict()
+        for key_node, value_node in node.value:
+            key = self.construct_object(key_node, deep=deep)
+            try:
+                hash(key)
+            except TypeError, exc:
+                raise yaml.constructor.ConstructorError('while constructing a mapping',
+                    node.start_mark, 'found unacceptable key (%s)' % exc, key_node.start_mark)
+            value = self.construct_object(value_node, deep=deep)
+            mapping[key] = value
+        return mapping
+
+if __name__ == '__main__':
+    import textwrap
+
+    sample = """
+    one:
+        two: fish
+        red: fish
+        blue: fish
+    two:
+        a: yes
+        b: no
+        c: null
+    """
+
+    data = yaml.load(textwrap.dedent(sample), OrderedDictYAMLLoader)
+
+    assert type(data) is OrderedDict
+    print data
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