bteng

5-minute Quick Start

This is the recommended first BTEng program. It uses TreeBuilder to construct the tree and TreeExecutor to run it.

Create quickstart.py:

from bteng import Blackboard, NodeStatus, TreeBuilder, TreeExecutor

bb = Blackboard.create("quickstart")
bb.set("battery_ok", True)

tree = (
    TreeBuilder(blackboard=bb)
    .tree_id("FirstTree")
    .sequence("mission")
        .condition("BatteryOK", lambda: bb.get("battery_ok", False))
        .action("Navigate", lambda: NodeStatus.SUCCESS)
    .end()
    .build()
)

executor = TreeExecutor()
executor.set_tree(tree)

status = executor.tick_until_result(max_ticks=10)
print(status)

Run it:

python3 quickstart.py

Expected output:

NodeStatus.SUCCESS

What happened

The tree uses a Sequence, which means:

1. Tick BatteryOK.
2. If BatteryOK succeeds, tick Navigate.
3. Return SUCCESS only if both children succeed.

If the condition fails, the action is not run:

bb.set("battery_ok", False)

Expected output:

NodeStatus.FAILURE

Common mistakes

Mistake	Fix
Forgetting .end()	Close every sequence, fallback, parallel, and decorator scope with .end()
Starting with BehaviorTreeEngine	Use TreeBuilder + TreeExecutor for new code
Reusing blackboard names across tests	Call Blackboard.reset("name") in test teardown
Confusing literals and blackboard keys	Use .literal("port", value) for static values and .map("port", "key") for blackboard lookup
Returning arbitrary objects from actions	Return NodeStatus.SUCCESS, NodeStatus.FAILURE, NodeStatus.RUNNING, or a boolean for simple inline nodes

Next: Which API should I use?.

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