py-behavior-tree

A C++ extension for Python of Behavior Tree

Prerequisite

• Python v2.7+
• cmake v3.0+

Build

git clone https://github.com/adonis0147/py-behavior-tree
mkdir build
cd build
cmake ..
make

Quick Start

Tick Functions

The module implements several tick functions for a node in behavior tree.

• tick_leaf: CallPythonFunction
• tick_node: TickNode
• run_until_success: RunUntilSuccess
• run_until_fail: RunUntilFail
• mem_run_until_success: MemRunUntilSuccess
• mem_run_until_fail: MemRunUntilFail
• report_success: ReportSuccess
• report_failure: ReportFailure
• revert_status: RevertStatus

More functions can be found in behavior_tree.FUNCTIONS_INDEX.

Add Nodes

You can call the behavior_tree.add_node method to add a node. However, there is a subtle difference between adding leaf nodes and non-leaf nodes.

For a leaf node which is used to call Python function, you should pass Python function to the method:

import behavior_tree

def foo():
  print 'Hello, world!'
  return behavior_tree.SUCCESS
  
behavior_tree.add_node(1, behavior_tree.FUNCTIONS_INDEX['tick_leaf'], function=foo)

For a non-leaf node, you should pass tick function and children nodes to the method:

behavior_tree.add_node(2, behavior_tree.FUNCTIONS_INDEX['tick_node'], children=[1])

Tick A Tree

1. create the root of the tree

  root = behavior_tree.Root(2)

2. tick the root

  root.tick()

3. the followings are the result in terminal

  Hello, world!

About Hotfix

Nodes are identified by id and you can change the tick function, the children nodes and the Python function of a node by calling the behavior_tree.add_node.

def bar():
  print 'Hello, hotfix!'
  return behavior_tree.SUCCESS

behavior_tree.add_node(1, behavior_tree.FUNCTIONS_INDEX['tick_leaf'], function=bar)

root.tick()

The result will be changed to Hello, hotfix!.

The nodes increment by id and will not be freed until the process terminates. Therefore, if you change the children nodes of a node, the memory of the old useless children nodes will not be released.

def baz():
  print 'Hello, new child!'
  return behavior_tree.SUCCESS

behavior_tree.add_node(3, behavior_tree.FUNCTIONS_INDEX['tick_leaf'], function=baz)

behavior_tree.add_node(2, behavior_tree.FUNCTIONS_INDEX['tick_node'], children=[3])

Node 1, Node 2, and Node 3 are all in the memory.

Related Project

• profile-viewer - Profile viewer for behavior tree