# How to access inherited attributes **URL:** \ **Category:** How-to Guides\ **Tags:** automator\ **Created:** [October 13, 2025, 9:50am UTC](https://forum.sensmetry.com/t/how-to-access-inherited-attributes/254 "2025-10-13T09:50:53Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Axel](https://avatars.discourse-cdn.com/v4/letter/a/6de8d8/32.png) [@Axel](https://forum.sensmetry.com/u/Axel)\ **Post date:** [October 13, 2025, 9:50am UTC](https://forum.sensmetry.com/t/how-to-access-inherited-attributes/254/1 "2025-10-13T09:50:53Z")
I have a part def where an attribute is defined, and then in a part usage I want to access the value of the attribute which I expect to be inherited. ```auto part def MyPartDef { attribute attr1 = 1; attribute attr2 = 2; attribute attrSum = attr1 + attr2; } part myPartUsage : MyPartDef; ``` In automator I’ve got this script: ```python def get_node(model: syside.Model, qualified_name: Sequence[str]) -> syside.Element: # Using the function provided in syside_helpers.py in the state machine example def get_attribute_value(node: syside.AttributeUsage): return syside.Compiler().evaluate(node.feature_value_expression)[0] print(get_node(model, ['MyPartDef','attrSum'])) print(get_attribute_value(get_node(model, ['MyPartDef','attrSum']))) print(get_node(model, ['myPartUsage'])) print(get_node(model, ['myPartUsage','attr1'])) ``` The output becomes: ```auto MyPartDef::attrSum 3 myPartUsage --------------------------------------------------------------------------- KeyError Traceback (most recent call last) ... File XXXXXXX, in _get_node_by_qualified_name(node, qualified_name) 31 for segment in qualified_name: 32 assert isinstance(current_node, syside.Namespace) ---> 33 current_node = current_node[segment] 34 return current_node KeyError: "No member named 'attr1' exists in this namespace" ``` Surely it is not an incorrect expectation that the attributes in the defintion would be inherited by the usages? Please advise. ---
**Author:** ![Daumantas](https://yyz2.discourse-cdn.com/flex008/user_avatar/forum.sensmetry.com/daumantas/32/19_2.png) [@Daumantas](https://forum.sensmetry.com/u/Daumantas)\ **Post date:** [October 13, 2025, 11:08am UTC](https://forum.sensmetry.com/t/how-to-access-inherited-attributes/254/2 "2025-10-13T11:08:04Z")
Hi @Axel, `Namespace. __getitem__ ` is intended to only return direct members which can be done cheaply, as opposed to an expensive graph search walking the inheritance and import graph. Inherited and imported members are not inlined to keep memory usage down. At the moment you will have to walk the inheritance graph manually: ```py queue: list[syside.Namespace] = [node] visited: set[syside.Namespace] = set() while queue: element = queue.pop(0) if isinstance(element, syside.Feature): element = element.feature_target if element in visited: continue visited.add(element) child = element.get_member(name) if child is not None: return child if isinstance(element, syside.Type): queue[0:0] = element.heritage.elements return None ``` High-level API is a work-in-progress. ---
**Author:** ![Axel](https://avatars.discourse-cdn.com/v4/letter/a/6de8d8/32.png) [@Axel](https://forum.sensmetry.com/u/Axel)\ **Post date:** [October 13, 2025, 4:02pm UTC](https://forum.sensmetry.com/t/how-to-access-inherited-attributes/254/3 "2025-10-13T16:02:07Z")
Hi @Daumantas, thanks for your reply. I am able to use the code you provided to retrieve the properties of the part definition. Wrapping it in a function `get_namespace_member()` I am able to do this: ```python part = get_node(model, ["myPartUsage"]) attr1 = get_namespace_member(part, "attr1") attr2 = get_namespace_member(part, "attr2") attrSum = get_namespace_member(part, "attrSum") print(attr1, "=", get_attribute_value(attr1)) print(attr2, "=", get_attribute_value(attr2)) print(attrSum, "=", get_attribute_value(attrSum)) ``` Which prints this: ```auto MyPartDef::attr1 = 1 MyPartDef::attr2 = 2 MyPartDef::attrSum = 3 ``` Now I tried to mix things up a bit by redefining the value of `attr1`, in the hope that `attrSum` would calculate a new value. For me, this is the reason behind this whole exercise: **to define a calculated attribute in a part definition, and be able to re-use that calculation in the part usages**. I changed the sysml snippet to this: ```auto part def MyPartDef { attribute attr1 default 1; attribute attr2 = 2; attribute attrSum = attr1 + attr2; } part myPartUsage : MyPartDef { attribute redefines attr1 = 10; } ``` And now when I run the same python code as above, the printout is instead this: ```auto myPartUsage::attr1 = 10 MyPartDef::attr2 = 2 MyPartDef::attrSum = 3 ``` As you see, the value of `attrSum` is not changing to 12 as I had hoped to see. Is there some different to accomplish this? Or am I running into a limitation of the current implementation of automator? ---
**Author:** ![Daumantas](https://yyz2.discourse-cdn.com/flex008/user_avatar/forum.sensmetry.com/daumantas/32/19_2.png) [@Daumantas](https://forum.sensmetry.com/u/Daumantas)\ **Post date:** [October 14, 2025, 6:23am UTC](https://forum.sensmetry.com/t/how-to-access-inherited-attributes/254/4 "2025-10-14T06:23:07Z")
There is a `Compiler.evaluate_feature` method that will do what you would expect by taking redefinitions into account: ```py result, report = compiler.evaluate_feature( feature=feature, scope=owning_type ) ``` Here, `feature` can be `MyPartDef::attrSum` and `owning_type` - `myPartUsage`, and it will correctly evaluate `attrSum` to `12`. > **Summary** > > ```python > import syside > > SRC = """\ > part def MyPartDef { > attribute attr1 default 1; > attribute attr2 = 2; > attribute attrSum = attr1 + attr2; > } > > part myPartUsage : MyPartDef { > attribute redefines attr1 = 10; > } > """ > > model, _ = syside.load_model(sysml_source=SRC) > with model.user_docs[0].lock() as doc: > pass > > compiler = syside.Compiler() > attr1 = ( > doc.root_node["MyPartDef"] > .cast(syside.PartDefinition)["attrSum"] > .cast(syside.AttributeUsage) > ) > usage = doc.root_node["myPartUsage"].cast(syside.PartUsage) > > result, report = compiler.evaluate_feature(attr1, scope=usage) > > assert not report.fatal, str(report.diagnostics) > print(result) # prints 12 > > ``` ---
**Author:** ![Axel](https://avatars.discourse-cdn.com/v4/letter/a/6de8d8/32.png) [@Axel](https://forum.sensmetry.com/u/Axel)\ **Post date:** [October 14, 2025, 10:22am UTC](https://forum.sensmetry.com/t/how-to-access-inherited-attributes/254/5 "2025-10-14T10:22:19Z")
Greatly appreciated @Daumantas, `syside.Compiler().evaluate_feature()` was precisely what I needed in this case. This brings me to the next step of what I am trying to accomplish: **using automator, I want to change the value of an inherited attribute**. So if my model is like this: ```auto part def MyPartDef { attribute attr1 default 1; attribute attr2 default 2; attribute attrSum = attr1 + attr2; } part myPartUsage : MyPartDef { attribute redefines attr1 = 10; } ``` I want to use automator to change the value of `myPartUsage.attr2`, for example to `50`. I know how change the value of an attribute usage in this way: ```python value_node = node.feature_value_member.set_member_element(syside.LiteralInteger)[1] value_node.value = 50 ``` But when I try this on the inherited attribute, as accessed in the way you showed earlier, with my `get_namespace_member()` function, the value that gets changed in the attribute in the definition instead of the usage: `MyPartDef.attr2` Is it possible to edit the value of an inherited attribute in this way? Are you required to redefine the attribute with a line like `attribute redefines attr2` in the part usage in order to be able to change the value only for that usage? ---
**Author:** ![Daumantas](https://yyz2.discourse-cdn.com/flex008/user_avatar/forum.sensmetry.com/daumantas/32/19_2.png) [@Daumantas](https://forum.sensmetry.com/u/Daumantas)\ **Post date:** [October 14, 2025, 10:25am UTC](https://forum.sensmetry.com/t/how-to-access-inherited-attributes/254/6 "2025-10-14T10:25:38Z")
You will need to create an attribute with the required redefinition: ```py _, attribute = my_part_usage.children.append( syside.FeatureMembership, syside.AttributeUsage ) attribute.heritage.append(syside.Redefinition, attr2) ``` You can then change it’s value as before.