added python bindings #8

shaur-k · 2025-06-19T21:08:42Z

please tear me apart here

The way this works is that we basically serialize objects in C++ to Python and then back (hence "binding" objects to and from C++). the underlying Python is well abstracted outside of the JSON Serialization functions that we create a helper for (I couldn't use concepts and didn't have a great way to avoid SFINAE picking the more simple fromJSON function I wrote).

Here's some documentation to pybind: https://pybind11.readthedocs.io/en/latest/

commit 47f067c Author: shaur-k <[email protected]> Date: Thu Jun 19 14:53:45 2025 -0600 feat: clean up old PR for new version of BTCPP commit 8c6cfac Author: shaur-k <[email protected]> Date: Thu Jun 19 13:16:13 2025 -0600 temp commit 6a6f86e Merge: 890396c 1b9e0e2 Author: shaur-k <[email protected]> Date: Thu Jun 19 12:07:36 2025 -0600 Merge branch 'master' into python-bindings commit 890396c Author: Kyle Cesare <[email protected]> Date: Tue Sep 5 23:45:06 2023 -0600 Fix setup.py package attributes. commit fb33788 Author: Kyle Cesare <[email protected]> Date: Tue Sep 5 21:57:19 2023 -0600 Add useful note for ex05 on shared lib location. commit 632eb66 Author: Kyle Cesare <[email protected]> Date: Tue Sep 5 21:55:52 2023 -0600 Clean up dummy node use in ex05. commit 1a7ac0a Author: Kyle Cesare <[email protected]> Date: Tue Sep 5 21:48:23 2023 -0600 Properly specify __all__ for btpy module. commit b425c91 Author: Kyle Cesare <[email protected]> Date: Mon Sep 4 19:17:31 2023 -0600 Add docs for `JsonExporter::fromJson`. commit 2584aec Author: Kyle Cesare <[email protected]> Date: Mon Sep 4 19:03:16 2023 -0600 Add default impl of AsyncActionNode#on_halted commit 04f435d Author: Kyle Cesare <[email protected]> Date: Mon Sep 4 19:03:07 2023 -0600 Add `halt_tree` binding and use in demo commit 535ea88 Author: Kyle Cesare <[email protected]> Date: Mon Sep 4 18:56:14 2023 -0600 Improve python example README commit 93b58c3 Author: Kyle Cesare <[email protected]> Date: Mon Sep 4 18:56:08 2023 -0600 Formatting. commit 0ee0a20 Author: Kyle Cesare <[email protected]> Date: Mon Sep 4 18:55:57 2023 -0600 Fix some string-embedded XML indentation. commit 0786475 Author: Kyle Cesare <[email protected]> Date: Mon Sep 4 18:54:11 2023 -0600 Don't make Py_StatefulActionNode final. commit 4ad738c Author: Kyle Cesare <[email protected]> Date: Sun Sep 3 19:16:29 2023 -0600 Add some docs to Python ex06. commit 84ae12d Author: Kyle Cesare <[email protected]> Date: Sun Sep 3 19:04:27 2023 -0600 Add some type hints to the Python code commit 46929a8 Author: Kyle Cesare <[email protected]> Date: Sun Sep 3 12:31:00 2023 -0600 Move Python-related source files into subdirectory. commit 9d8db3c Author: Kyle Cesare <[email protected]> Date: Sun Sep 3 11:57:13 2023 -0600 Clean up Python example XMLs. commit ee7f464 Author: Kyle Cesare <[email protected]> Date: Sat Sep 2 11:08:42 2023 -0600 Modify py::type argument to support older pybind commit fdc2232 Author: Kyle Cesare <[email protected]> Date: Fri Sep 1 22:18:04 2023 -0600 Add pyproject.toml/setup.py for building wheels. commit 2c1b18a Author: Kyle Cesare <[email protected]> Date: Fri Sep 1 21:40:14 2023 -0600 Use docstring as tree node description. commit 1a69d3a Author: Kyle Cesare <[email protected]> Date: Sat Aug 26 22:47:56 2023 -0600 Clean up Python ex06. commit 0e35ac0 Author: Kyle Cesare <[email protected]> Date: Fri Sep 1 19:35:57 2023 -0600 Move some dummy_nodes definitions to cpp file to fix linker error commit 83caef7 Author: Kyle Cesare <[email protected]> Date: Fri Sep 1 19:35:46 2023 -0600 Add missing pybind11 dependency to package.xml commit c703efd Author: Kyle Cesare <[email protected]> Date: Sat Aug 19 19:49:01 2023 -0600 Implement coroutine-based Python nodes. commit 4448376 Author: Kyle Cesare <[email protected]> Date: Sat Aug 19 19:07:54 2023 -0600 Add pybind11 conan dependency. commit 21d450e Author: Kyle Cesare <[email protected]> Date: Sat Aug 19 18:52:52 2023 -0600 Add `BehaviorTreeFactory.register_from_plugin` binding. commit d1fe0e3 Author: Kyle Cesare <[email protected]> Date: Sat Aug 19 18:52:39 2023 -0600 Implement C++ <-> Python type interop via JSON. commit cfa553a Author: Kyle Cesare <[email protected]> Date: Sat Aug 19 12:52:01 2023 -0600 Disable zero variadic arg warning. commit 7927e67 Author: Kyle Cesare <[email protected]> Date: Sat Aug 19 12:51:44 2023 -0600 Fix onHalted override copy-paste error. commit 712370b Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 12:30:01 2023 -0600 Add useful command for ex04. commit dc9e953 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 12:28:16 2023 -0600 Fix typo in ex04. commit ed78e84 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 12:27:34 2023 -0600 Fix NodeStatus enum value ordering. commit 2a22fa8 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 12:05:05 2023 -0600 Add note about Py_getInput return value. commit 37ae114 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 12:01:52 2023 -0600 Add simple README. commit adf5cef Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 11:56:52 2023 -0600 Add ROS2 interop example. commit 404a195 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 11:56:38 2023 -0600 Add builder args to be passed to node ctors. commit 9493f10 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 11:56:23 2023 -0600 Return None if blackboard value doesn't exist. commit 6188c21 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 11:10:10 2023 -0600 Ignore pycache. commit b22772e Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 10:55:49 2023 -0600 Put generic methods on abstract base class. commit 17da541 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 10:54:59 2023 -0600 Clean up port handling. commit 4ff5673 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 10:54:37 2023 -0600 Export minimal set of identifiers to Python lib. commit 351c33a Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 10:54:25 2023 -0600 Use proper PYBIND11_OVERRIDE macros. commit 1f9db33 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 10:30:18 2023 -0600 Eliminate some code duplication. commit f560500 Author: Kyle Cesare <[email protected]> Date: Sun Aug 13 00:22:11 2023 -0600 Add stateful action bindings. commit 9fdcda1 Author: Kyle Cesare <[email protected]> Date: Sat Aug 12 23:09:20 2023 -0600 Implement minimal Python bindings to SyncActionNode

henrygerardmoore · 2025-06-19T21:24:51Z

I can't review this all yet, but would it be possible to add a bunch of tests that serialize a type back and forth and ensure it's the same? Or serialize it, change it, then test that the deserialized one has that change? Those or some set of tests like them are probably necessary before we should consider merging this big of a change, IMO

pac48 · 2025-06-19T23:37:29Z

I think we lost this code.

shaur-k · 2025-06-20T14:38:12Z

throwing back to draft to finish some implementation and clean up that I found last night

shaur-k · 2025-06-20T21:19:25Z

this is ready again, except @henrygerardmoore i know i need to add some better tests, but you can build this and run the python_examples to see what works

griswaldbrooks

first pass

btpy/__init__.py

griswaldbrooks · 2025-07-02T19:35:16Z

include/behaviortree_cpp/contrib/pybind11_json.hpp

+
+    inline py::object from_json(const nl::json& j)
+    {
+        if (j.is_null())


It feels like you should be able to change this to use a std::variant or function map using https://json.nlohmann.me/api/basic_json/type/

You can even do some sort of mapping of the py:: types. This if/else tree is just kind of hard to look at.

(and of course if you are returning, the you should use an if not an else if

griswaldbrooks · 2025-07-02T19:39:44Z

include/behaviortree_cpp/contrib/pybind11_json.hpp

+        }
+    }
+
+    inline nl::json to_json(const py::handle& obj)


Same comment as above, something should be done to simplify this, more to look like a mapping between objects

griswaldbrooks · 2025-07-02T19:40:26Z

include/behaviortree_cpp/contrib/pybind11_json.hpp

+                    return s;
+                }
+            }
+            catch (...)


usually if you don't swallow the exception?

griswaldbrooks · 2025-07-02T21:45:28Z

src/python/bindings.cpp

+{
+  py::object obj;
+
+  // The input could not exist on the blackboard, in which case we return Python


Suggested change

// The input could not exist on the blackboard, in which case we return Python

// The input was not on the blackboard, in which case we return Python

griswaldbrooks · 2025-07-02T21:47:39Z

src/python/bindings.cpp

+  }
+  catch(py::error_already_set& e)
+  {
+    // If that fails, then assume it's a string literal with quotation marks


griswaldbrooks · 2025-07-02T21:49:55Z

src/python/bindings.cpp

+    py::object obj;
+    obj = type(name, config, *args, **kwargs);


Does

Suggested change

py::object obj;

obj = type(name, config, *args, **kwargs);

py::object obj = type(name, config, *args, **kwargs);

work?

griswaldbrooks · 2025-07-02T21:53:03Z

src/python/bindings.cpp

+    py::object obj;
+    obj = type(name, config, *args, **kwargs);
+
+    // TODO: Increment the object's reference count or else it


What is this? Is this the recommended pattern?

griswaldbrooks · 2025-07-02T21:55:19Z

src/python/types.cpp

+#else
+__attribute__((visibility("default")))
+#endif
+    bool toPythonObject(const BT::Any& val, pybind11::object& dest)


Suggested change

bool toPythonObject(const BT::Any& val, pybind11::object& dest)

bool toPythonObject(const BT::Any& val, pybind11::object& dest)

shaur-k requested review from griswaldbrooks, EzraBrooks, pac48, dsobek, henrygerardmoore and dyackzan June 19, 2025 21:08

shaur-k self-assigned this Jun 19, 2025

shaur-k changed the title ~~Squashed commit of the following:~~ added python bindings Jun 19, 2025

Merge branch 'master' into python-bindings

38fb950

shaur-k force-pushed the python-bindings branch 2 times, most recently from 2899a69 to 86416c5 Compare June 20, 2025 03:26

shaur-k marked this pull request as draft June 20, 2025 14:37

fix: guards for template specialization of pyobject fromJson()

5f3220e

shaur-k force-pushed the python-bindings branch from 86416c5 to 5f3220e Compare June 20, 2025 20:51

shaur-k marked this pull request as ready for review June 20, 2025 20:51

EzraBrooks removed request for EzraBrooks, henrygerardmoore, dyackzan and pac48 June 23, 2025 15:19

griswaldbrooks assigned griswaldbrooks and unassigned shaur-k Jun 23, 2025

shaur-k assigned shaur-k and unassigned griswaldbrooks Jul 1, 2025

griswaldbrooks requested changes Jul 2, 2025

View reviewed changes

	// The input could not exist on the blackboard, in which case we return Python
	// The input was not on the blackboard, in which case we return Python

	py::object obj;
	obj = type(name, config, args, *kwargs);
	py::object obj = type(name, config, args, *kwargs);

	bool toPythonObject(const BT::Any& val, pybind11::object& dest)
	bool toPythonObject(const BT::Any& val, pybind11::object& dest)

added python bindings #8

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added python bindings #8

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shaur-k commented Jun 19, 2025

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henrygerardmoore commented Jun 19, 2025 •

edited

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