#!/usr/bin/env python
#
# License: BSD
# https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
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# Documentation
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"""
While a graph of connected behaviours and composites form a tree in their own right
(i.e. it can be initialised and ticked), it is usually convenient to wrap your tree
in another class to take care of alot of the housework and provide some extra bells
and whistles that make your tree flourish.
.. image:: images/yggdrasil.jpg
:width: 200px
:align: center
This package provides a default reference implementation that is directly usable, but
can also be easily used as inspiration for your own tree custodians.
"""
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# Imports
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import multiprocessing
import time
from . import behaviour
from . import common
from . import composites
from . import visitors
CONTINUOUS_TICK_TOCK = -1
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# Trees
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[docs]class BehaviourTree(object):
"""
Grow, water, prune your behaviour tree with this, the default reference
implementation. It features a few enhancements to provide richer logging,
introspection and dynamic management of the tree itself:
* Pre and post tick handlers to execute code automatically before and after a tick
* Visitor access to the parts of the tree that were traversed in a tick
* Subtree pruning and insertion operations
* Continuous tick-tock support
.. seealso:: The :ref:`py-trees-demo-tree-stewardship-program` program demonstrates the above features.
Args:
root (:class:`~py_trees.behaviour.Behaviour`): root node of the tree
Attributes:
count (:obj:`int`): number of times the tree has been ticked.
root (:class:`~py_trees.behaviour.Behaviour`): root node of the tree
visitors ([:mod:`~py_trees.visitors`]): entities that visit traversed parts of the tree when it ticks
pre_tick_handlers ([:obj:`func`]): functions that run before the entire tree is ticked
post_tick_handlers ([:obj:`func`]): functions that run after the entire tree is ticked
Raises:
TypeError: if root variable is not an instance of :class:`~py_trees.behaviour.Behaviour`
"""
def __init__(self, root: behaviour.Behaviour):
self.count = 0
if not isinstance(root, behaviour.Behaviour):
raise TypeError("root node must be an instance of 'py_trees.behaviour.Behaviour' [{}]".format(type(root)))
self.root = root
self.visitors = []
self.pre_tick_handlers = []
self.post_tick_handlers = []
self.interrupt_tick_tocking = False
self.tree_update_handler = None # child classes can utilise this one
[docs] def add_pre_tick_handler(self, handler):
"""
Add a function to execute before the tree is ticked. The function must have
a single argument of type :class:`~py_trees.trees.BehaviourTree`.
Some ideas that are often used:
* logging (to file or stdout)
* modifications on the tree itself (e.g. starting a new plan)
Args:
handler (:obj:`func`): function
"""
self.pre_tick_handlers.append(handler)
[docs] def add_post_tick_handler(self, handler):
"""
Add a function to execute after the tree has ticked. The function must have
a single argument of type :class:`~py_trees.trees.BehaviourTree`.
Some ideas that are often used:
* logging
* modifications on the tree itself (e.g. closing down a plan)
* sending data to visualisation tools
* introspect the state of the tree to make and send reports
Args:
handler (:obj:`func`): function
"""
self.post_tick_handlers.append(handler)
[docs] def prune_subtree(self, unique_id):
"""
Prune a subtree given the unique id of the root of the subtree.
Args:
unique_id (uuid.UUID): unique id of the subtree root
Returns:
:obj:`bool`: success or failure of the operation
Raises:
RuntimeError: if unique id is the behaviour tree's root node id
"""
# TODO: convert this to throwing exceptions instead
if self.root.id == unique_id:
raise RuntimeError("may not prune the root node")
for child in self.root.iterate():
if child.id == unique_id:
parent = child.parent
if parent is not None:
parent.remove_child(child)
if self.tree_update_handler is not None:
self.tree_update_handler(self.root)
return True
return False
[docs] def insert_subtree(self, child, unique_id, index):
"""
Insert a subtree as a child of the specified parent. If the parent
is found, this directly calls the parent's
:meth:`~py_trees.composites.Composite.insert_child`
method using the child and index arguments.
Args:
child (:class:`~py_trees.behaviour.Behaviour`): subtree to insert
unique_id (uuid.UUID): unique id of the parent
index (:obj:`int`): insert the child at this index, pushing all children after it back one.
Returns:
:obj:`bool`: suceess or failure (parent not found) of the operation
Raises:
TypeError: if the parent is not a :class:`~py_trees.composites.Composite`
.. todo::
Could use better, more informative error handling here. Especially if the insertion
has its own error handling (e.g. index out of range). Could also use a different api
that relies on the id of the sibling node it should be inserted before/after.
"""
# TODO: convert this to throwing exceptions instead
for node in self.root.iterate():
if node.id == unique_id:
if not isinstance(node, composites.Composite):
raise TypeError("parent must be a Composite behaviour.")
node.insert_child(child, index)
if self.tree_update_handler is not None:
self.tree_update_handler(self.root)
return True
return False
[docs] def replace_subtree(self, unique_id, subtree):
"""
Replace the subtree with the specified id for the new subtree.
This is a common pattern where we'd like to swap out a whole sub-behaviour for another one.
Args:
unique_id (uuid.UUID): unique id of the parent
subtree (:class:`~py_trees.behaviour.Behaviour`): root behaviour of the subtree
Raises
AssertionError: if unique id is the behaviour tree's root node id
Returns:
:obj:`bool`: suceess or failure of the operation
"""
# TODO: convert this to throwing exceptions instead
if self.root.id == unique_id:
raise RuntimeError("may not replace the root node")
for child in self.root.iterate():
if child.id == unique_id:
parent = child.parent
if parent is not None:
parent.replace_child(child, subtree)
if self.tree_update_handler is not None:
self.tree_update_handler(self.root)
return True
return False
[docs] def setup(self, timeout: float=common.Duration.INFINITE, visitor: visitors.VisitorBase=None):
"""
Crawls across the tree calling :meth:`~py_trees.behaviour.Behaviour.setup`
on each behaviour.
Visitors can optionally be provided to provide a node-by-node analysis
on the result of each node's :meth:`~py_trees.behaviour.Behaviour.setup`
before the next node's :meth:`~py_trees.behaviour.Behaviour.setup` is called.
This is useful on trees with relatively long setup times to progressively
report out on the current status of the operation.
Args:
timeout (:obj:`float`): time (s) to wait (use common.Duration.INFINITE to block indefinitely)
visitor (:class:`~py_trees.visitors.VisitorBase`): runnable entities on each node after it's setup
Raises:
Exception: be ready to catch if any of the behaviours raise an exception
"""
def visited_setup():
for node in self.root.iterate():
node.setup()
if visitor is not None:
node.visit(visitor)
if timeout == common.Duration.INFINITE:
visited_setup()
else:
setup_process = multiprocessing.Process(target=visited_setup)
setup_process.start()
setup_process.join(timeout=timeout)
if setup_process.is_alive(): # could just as easily have checked the result of join
setup_process.terminate()
raise RuntimeError("tree setup() timed out")
[docs] def tick(self, pre_tick_handler=None, post_tick_handler=None):
"""
Tick the tree just once and run any handlers before and after the tick.
This optionally accepts some one-shot handlers (c.f. those added by
:meth:`~py_trees.trees.BehaviourTree.add_pre_tick_handler` and :meth:`~py_trees.trees.BehaviourTree.add_post_tick_handler`
which will be automatically run every time).
The handler functions must have a single argument of type :class:`~py_trees.trees.BehaviourTree`.
Args:
pre_tick_handler (:obj:`func`): function to execute before ticking
post_tick_handler (:obj:`func`): function to execute after ticking
"""
# pre
for handler in self.pre_tick_handlers:
handler(self)
if pre_tick_handler is not None:
pre_tick_handler(self)
for visitor in self.visitors:
visitor.initialise()
# tick
for node in self.root.tick():
for visitor in [visitor for visitor in self.visitors if not visitor.full]:
node.visit(visitor)
for node in self.root.iterate():
for visitor in [visitor for visitor in self.visitors if visitor.full]:
node.visit(visitor)
# post
for handler in self.post_tick_handlers:
handler(self)
if post_tick_handler is not None:
post_tick_handler(self)
self.count += 1
[docs] def tick_tock(self, sleep_ms, number_of_iterations=CONTINUOUS_TICK_TOCK, pre_tick_handler=None, post_tick_handler=None):
"""
Tick continuously with a sleep interval as specified. This optionally accepts some handlers that will
be used for the duration of this tick tock (c.f. those added by
:meth:`~py_trees.trees.BehaviourTree.add_pre_tick_handler` and :meth:`~py_trees.trees.BehaviourTree.add_post_tick_handler`
which will be automatically run every time).
The handler functions must have a single argument of type :class:`~py_trees.trees.BehaviourTree`.
Args:
sleep_ms (:obj:`float`): sleep this much between ticks (milliseconds)
number_of_iterations (:obj:`int`): number of iterations to tick-tock
pre_tick_handler (:obj:`func`): function to execute before ticking
post_tick_handler (:obj:`func`): function to execute after ticking
"""
tick_tocks = 0
while not self.interrupt_tick_tocking and (tick_tocks < number_of_iterations or number_of_iterations == CONTINUOUS_TICK_TOCK):
self.tick(pre_tick_handler, post_tick_handler)
try:
time.sleep(sleep_ms / 1000.0)
except KeyboardInterrupt:
break
tick_tocks += 1
self.interrupt_tick_tocking = False
[docs] def tip(self):
"""
Get the *tip* of the tree.
This corresponds to the the deepest node that was running before the
subtree traversal reversed direction and headed back to this node.
Returns:
:class:`~py_trees.behaviour.Behaviour` or :obj:`None`: child behaviour, itself or :obj:`None` if its status is :data:`~py_trees.common.Status.INVALID`
.. seealso:: :meth:`~py_trees.behaviour.Behaviour.tip`
"""
return self.root.tip()
[docs] def interrupt(self):
"""
Interrupt tick-tock if it is tick-tocking. Note that this will permit a currently
executing tick to finish before interrupting the tick-tock.
"""
self.interrupt_tick_tocking = True
[docs] def destroy(self):
"""
Destroy the tree by stopping the root node.
"""
self.root.stop()