#!/usr/bin/env python
#
# License: BSD
# https://raw.githubusercontent.com/splintered-reality/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################
"""
Composites are responsible for directing the path traced through
the tree on a given tick (execution). They are the **factories**
(Sequences and Parallels) and **decision makers** (Selectors) of a behaviour
tree.
.. graphviz:: dot/composites.dot
:align: center
:caption: PyTree Composites
Composite behaviours typically manage children and apply some logic to the way
they execute and return a result, but generally don't do anything themselves.
Perform the checks or actions you need to do in the non-composite behaviours.
Most any desired functionality can be authored with a combination of these
three composites. In fact, it is precisely this feature that makes behaviour
trees attractive - it breaks down complex decision making logic to just three
primitive elements. It is possible and often desirable to extend this set with
custom composites of your own, but think carefully before you do - in almost
every case, a combination of the existing composites will serve and as a
result, you will merely compound the complexity inherent in your tree logic.
This this makes it confoundingly difficult to design, introspect and debug. As
an example, design sessions often revolve around a sketched graph on a
whiteboard. When these graphs are composed of just five elements (Selectors,
Sequences, Parallels, Decorators and Behaviours), it is very easy to understand
the logic at a glance. Double the number of fundamental elements and you may as
well be back at the terminal parsing code.
.. tip:: You should never need to subclass or create new composites.
The basic operational modes of the three composites in this library are as follows:
* :class:`~py_trees.composites.Selector`: select a child to execute based on cascading priorities
* :class:`~py_trees.composites.Sequence`: execute children sequentially
* :class:`~py_trees.composites.Parallel`: execute children concurrently
This library does provide some flexibility in *how* each composite is implemented without
breaking the fundamental nature of each (as described above). Selectors and Sequences can
be configured with or without memory (resumes or resets if children are RUNNING) and
the results of a parallel can be configured to wait upon all children completing, succeed
on one, all or a subset thereof.
.. tip:: Follow the links in each composite's documentation to the relevant demo programs.
"""
##############################################################################
# Imports
##############################################################################
import itertools
import typing
from . import behaviour
from . import common
##############################################################################
# Composites
##############################################################################
[docs]class Composite(behaviour.Behaviour):
"""
The parent class to all composite behaviours, i.e. those that
have children.
Args:
name (:obj:`str`): the composite behaviour name
children ([:class:`~py_trees.behaviour.Behaviour`]): list of children to add
"""
[docs] def __init__(self,
name: typing.Union[str, common.Name]=common.Name.AUTO_GENERATED,
children: typing.List[behaviour.Behaviour]=None
):
super(Composite, self).__init__(name)
if children is not None:
for child in children:
self.add_child(child)
else:
self.children = []
self.current_child = None
############################################
# Worker Overrides
############################################
[docs] def stop(self, new_status=common.Status.INVALID):
"""
There is generally two use cases that must be supported here.
1) Whenever the composite has gone to a recognised state (i.e. :data:`~py_trees.common.Status.FAILURE` or SUCCESS),
or 2) when a higher level parent calls on it to truly stop (INVALID).
In only the latter case will children need to be forcibly stopped as well. In the first case, they will
have stopped themselves appropriately already.
Args:
new_status (:class:`~py_trees.common.Status`): behaviour will transition to this new status
"""
self.logger.debug("%s.stop()[%s]" % (self.__class__.__name__, "%s->%s" % (self.status, new_status) if self.status != new_status else "%s" % new_status))
# priority interrupted
if new_status == common.Status.INVALID:
self.current_child = None
for child in self.children:
child.stop(new_status)
# This part just replicates the Behaviour.stop function. We replicate it here so that
# the Behaviour logging doesn't duplicate the composite logging here, just a bit cleaner this way.
self.terminate(new_status)
self.status = new_status
self.iterator = self.tick()
[docs] def tip(self):
"""
Recursive function to extract the last running node of the tree.
Returns:
:class::`~py_trees.behaviour.Behaviour`: the tip function of the current child of this composite or None
"""
if self.current_child is not None:
return self.current_child.tip()
else:
return super().tip()
############################################
# Children
############################################
[docs] def add_child(self, child):
"""
Adds a child.
Args:
child (:class:`~py_trees.behaviour.Behaviour`): child to add
Raises:
TypeError: if the child is not an instance of :class:`~py_trees.behaviour.Behaviour`
RuntimeError: if the child already has a parent
Returns:
uuid.UUID: unique id of the child
"""
if not isinstance(child, behaviour.Behaviour):
raise TypeError("children must be behaviours, but you passed in {}".format(type(child)))
self.children.append(child)
if child.parent is not None:
raise RuntimeError("behaviour '{}' already has parent '{}'".format(child.name, child.parent.name))
child.parent = self
return child.id
[docs] def add_children(self, children):
"""
Append a list of children to the current list.
Args:
children ([:class:`~py_trees.behaviour.Behaviour`]): list of children to add
"""
for child in children:
self.add_child(child)
return self
[docs] def remove_child(self, child):
"""
Remove the child behaviour from this composite.
Args:
child (:class:`~py_trees.behaviour.Behaviour`): child to delete
Returns:
:obj:`int`: index of the child that was removed
.. todo:: Error handling for when child is not in this list
"""
if self.current_child is not None and (self.current_child.id == child.id):
self.current_child = None
if child.status == common.Status.RUNNING:
child.stop(common.Status.INVALID)
child_index = self.children.index(child)
self.children.remove(child)
child.parent = None
return child_index
[docs] def remove_all_children(self):
"""
Remove all children. Makes sure to stop each child if necessary.
"""
self.current_child = None
for child in self.children:
if child.status == common.Status.RUNNING:
child.stop(common.Status.INVALID)
child.parent = None
# makes sure to delete it for this class and all references to it
# http://stackoverflow.com/questions/850795/clearing-python-lists
del self.children[:]
[docs] def replace_child(self, child, replacement):
"""
Replace the child behaviour with another.
Args:
child (:class:`~py_trees.behaviour.Behaviour`): child to delete
replacement (:class:`~py_trees.behaviour.Behaviour`): child to insert
"""
self.logger.debug("%s.replace_child()[%s->%s]" % (self.__class__.__name__, child.name, replacement.name))
child_index = self.children.index(child)
self.remove_child(child)
self.insert_child(replacement, child_index)
child.parent = None
[docs] def remove_child_by_id(self, child_id):
"""
Remove the child with the specified id.
Args:
child_id (uuid.UUID): unique id of the child
Raises:
IndexError: if the child was not found
"""
child = next((c for c in self.children if c.id == child_id), None)
if child is not None:
self.remove_child(child)
else:
raise IndexError('child was not found with the specified id [%s]' % child_id)
[docs] def prepend_child(self, child):
"""
Prepend the child before all other children.
Args:
child (:class:`~py_trees.behaviour.Behaviour`): child to insert
Returns:
uuid.UUID: unique id of the child
"""
self.children.insert(0, child)
child.parent = self
return child.id
[docs] def insert_child(self, child, index):
"""
Insert child at the specified index. This simply directly calls
the python list's :obj:`insert` method using the child and index arguments.
Args:
child (:class:`~py_trees.behaviour.Behaviour`): child to insert
index (:obj:`int`): index to insert it at
Returns:
uuid.UUID: unique id of the child
"""
self.children.insert(index, child)
child.parent = self
return child.id
##############################################################################
# Selector
##############################################################################
[docs]class Selector(Composite):
"""
Selectors are the decision makers.
.. graphviz:: dot/selector.dot
A selector executes each of its child behaviours in turn until one of them
succeeds (at which point it itself returns :data:`~py_trees.common.Status.RUNNING` or :data:`~py_trees.common.Status.SUCCESS`,
or it runs out of children at which point it itself returns :data:`~py_trees.common.Status.FAILURE`.
We usually refer to selecting children as a means of *choosing between priorities*.
Each child and its subtree represent a decreasingly lower priority path.
.. note::
Switching from a low -> high priority branch causes a `stop(INVALID)` signal to be sent to the previously
executing low priority branch. This signal will percolate down that child's own subtree. Behaviours
should make sure that they catch this and *destruct* appropriately.
.. seealso:: The :ref:`py-trees-demo-selector-program` program demos higher priority switching under a selector.
Args:
name (:obj:`str`): the composite behaviour name
memory (:obj:`bool`): if :data:`~py_trees.common.Status.RUNNING` on the previous tick, resume with the :data:`~py_trees.common.Status.RUNNING` child
children ([:class:`~py_trees.behaviour.Behaviour`]): list of children to add
"""
[docs] def __init__(self, name="Selector", memory=False, children=None):
super(Selector, self).__init__(name, children)
self.memory = memory
[docs] def tick(self):
"""
Run the tick behaviour for this selector. Note that the status
of the tick is always determined by its children, not
by the user customised update function.
Yields:
:class:`~py_trees.behaviour.Behaviour`: a reference to itself or one of its children
"""
self.logger.debug("%s.tick()" % self.__class__.__name__)
# initialise
if self.status != common.Status.RUNNING:
# selector specific initialisation - leave initialise() free for users to
# re-implement without having to make calls to super()
self.logger.debug("%s.tick() [!RUNNING->reset current_child]" % self.__class__.__name__)
self.current_child = self.children[0] if self.children else None
# reset the children - don't need to worry since they will be handled
# a) prior to a remembered starting point, or
# b) invalidated by a higher level priority
# user specific initialisation
self.initialise()
# customised work
self.update()
# nothing to do
if not self.children:
self.current_child = None
self.stop(common.Status.FAILURE)
yield self
return
# starting point
if self.memory:
index = self.children.index(self.current_child)
# clear out preceding status' - not actually necessary but helps
# visualise the case of memory vs no memory
for child in itertools.islice(self.children, None, index):
child.stop(common.Status.INVALID)
else:
index = 0
# actual work
previous = self.current_child
for child in itertools.islice(self.children, index, None):
for node in child.tick():
yield node
if node is child:
if node.status == common.Status.RUNNING or node.status == common.Status.SUCCESS:
self.current_child = child
self.status = node.status
if previous is None or previous != self.current_child:
# we interrupted, invalidate everything at a lower priority
passed = False
for child in self.children:
if passed:
if child.status != common.Status.INVALID:
child.stop(common.Status.INVALID)
passed = True if child == self.current_child else passed
yield self
return
# all children failed, set failure ourselves and current child to the last bugger who failed us
self.status = common.Status.FAILURE
try:
self.current_child = self.children[-1]
except IndexError:
self.current_child = None
yield self
[docs] def stop(self, new_status=common.Status.INVALID):
"""
Stopping a selector requires setting the current child to none. Note that it
is important to implement this here instead of terminate, so users are free
to subclass this easily with their own terminate and not have to remember
that they need to call this function manually.
Args:
new_status (:class:`~py_trees.common.Status`): the composite is transitioning to this new status
"""
# retain information about the last running child if the new status is
# SUCCESS or FAILURE
if new_status == common.Status.INVALID:
self.current_child = None
Composite.stop(self, new_status)
##############################################################################
# Sequence
##############################################################################
[docs]class Sequence(Composite):
"""
Sequences are the factory lines of Behaviour Trees
.. graphviz:: dot/sequence.dot
A sequence will progressively tick over each of its children so long as
each child returns :data:`~py_trees.common.Status.SUCCESS`. If any child returns
:data:`~py_trees.common.Status.FAILURE` or :data:`~py_trees.common.Status.RUNNING` the sequence will halt and the parent will adopt
the result of this child. If it reaches the last child, it returns with
that result regardless.
.. note::
The sequence halts once it sees a child is RUNNING and then returns
the result. *It does not get stuck in the running behaviour*.
.. seealso:: The :ref:`py-trees-demo-sequence-program` program demos a simple sequence in action.
Args:
name: the composite behaviour name
memory: if :data:`~py_trees.common.Status.RUNNING` on the previous tick, resume with the :data:`~py_trees.common.Status.RUNNING` child
children: list of children to add
"""
[docs] def __init__(
self,
name: str="Sequence",
memory: bool=True,
children: typing.List[behaviour.Behaviour]=None
):
super(Sequence, self).__init__(name, children)
self.memory = memory
[docs] def tick(self):
"""
Tick over the children.
Yields:
:class:`~py_trees.behaviour.Behaviour`: a reference to itself or one of its children
"""
self.logger.debug("%s.tick()" % self.__class__.__name__)
# initialise
index = 0
if self.status != common.Status.RUNNING or not self.memory:
self.current_child = self.children[0] if self.children else None
for child in self.children:
if child.status != common.Status.INVALID:
child.stop(common.Status.INVALID)
# user specific initialisation
self.initialise()
else: # self.memory is True and status is RUNNING
index = self.children.index(self.current_child)
# customised work
self.update()
# nothing to do
if not self.children:
self.current_child = None
self.stop(common.Status.SUCCESS)
yield self
return
# actual work
for child in itertools.islice(self.children, index, None):
for node in child.tick():
yield node
if node is child and node.status != common.Status.SUCCESS:
self.status = node.status
yield self
return
try:
# advance if there is 'next' sibling
self.current_child = self.children[index + 1]
index += 1
except IndexError:
pass
self.stop(common.Status.SUCCESS)
yield self
##############################################################################
# Parallel
##############################################################################
[docs]class Parallel(Composite):
"""
Parallels enable a kind of concurrency
.. graphviz:: dot/parallel.dot
Ticks every child every time the parallel is run (a poor man's form of parallelism).
* Parallels will return :data:`~py_trees.common.Status.FAILURE` if any
child returns :py:data:`~py_trees.common.Status.FAILURE`
* Parallels with policy :class:`~py_trees.common.ParallelPolicy.SuccessOnAll`
only returns :py:data:`~py_trees.common.Status.SUCCESS` if **all** children
return :py:data:`~py_trees.common.Status.SUCCESS`
* Parallels with policy :class:`~py_trees.common.ParallelPolicy.SuccessOnOne`
return :py:data:`~py_trees.common.Status.SUCCESS` if **at least one** child
returns :py:data:`~py_trees.common.Status.SUCCESS` and others are
:py:data:`~py_trees.common.Status.RUNNING`
* Parallels with policy :class:`~py_trees.common.ParallelPolicy.SuccessOnSelected`
only returns :py:data:`~py_trees.common.Status.SUCCESS` if a **specified subset**
of children return :py:data:`~py_trees.common.Status.SUCCESS`
Policies :class:`~py_trees.common.ParallelPolicy.SuccessOnAll` and
:class:`~py_trees.common.ParallelPolicy.SuccessOnSelected` may be configured to be
*synchronised* in which case children that tick with
:data:`~py_trees.common.Status.SUCCESS` will be skipped on subsequent ticks until
the policy criteria is met, or one of the children returns
status :data:`~py_trees.common.Status.FAILURE`.
Parallels with policy :class:`~py_trees.common.ParallelPolicy.SuccessOnSelected` will
check in both the :meth:`~py_trees.behaviour.Behaviour.setup` and
:meth:`~py_trees.behaviour.Behaviour.tick` methods to to verify the
selected set of children is actually a subset of the children of this parallel.
.. seealso::
* :ref:`Context Switching Demo <py-trees-demo-context-switching-program>`
"""
[docs] def __init__(self,
name: typing.Union[str, common.Name]=common.Name.AUTO_GENERATED,
policy: common.ParallelPolicy.Base=common.ParallelPolicy.SuccessOnAll(),
children: typing.List[behaviour.Behaviour]=None
):
"""
Args:
name (:obj:`str`): the composite behaviour name
policy (:class:`~py_trees.common.ParallelPolicy`): policy to use for deciding success or otherwise
children ([:class:`~py_trees.behaviour.Behaviour`]): list of children to add
"""
super(Parallel, self).__init__(name, children)
self.policy = policy
[docs] def setup(self, **kwargs):
"""
Detect before ticking whether the policy configuration is invalid.
Args:
**kwargs (:obj:`dict`): distribute arguments to this
behaviour and in turn, all of it's children
Raises:
RuntimeError: if the parallel's policy configuration is invalid
Exception: be ready to catch if any of the children raise an exception
"""
self.logger.debug("%s.setup()" % (self.__class__.__name__))
self.validate_policy_configuration()
[docs] def tick(self):
"""
Tick over the children.
Yields:
:class:`~py_trees.behaviour.Behaviour`: a reference to itself or one of its children
Raises:
RuntimeError: if the policy configuration was invalid
"""
self.logger.debug("%s.tick()" % self.__class__.__name__)
self.validate_policy_configuration()
# reset
if self.status != common.Status.RUNNING:
self.logger.debug("%s.tick(): re-initialising" % self.__class__.__name__)
for child in self.children:
# reset the children, this ensures old SUCCESS/FAILURE status flags
# don't break the synchronisation logic below
if child.status != common.Status.INVALID:
child.stop(common.Status.INVALID)
self.current_child = None
# subclass (user) handling
self.initialise()
# nothing to do
if not self.children:
self.current_child = None
self.stop(common.Status.SUCCESS)
yield self
return
# process them all first
for child in self.children:
if self.policy.synchronise and child.status == common.Status.SUCCESS:
continue
for node in child.tick():
yield node
# determine new status
new_status = common.Status.RUNNING
self.current_child = self.children[-1]
try:
failed_child = next(child for child in self.children if child.status == common.Status.FAILURE)
self.current_child = failed_child
new_status = common.Status.FAILURE
except StopIteration:
if type(self.policy) is common.ParallelPolicy.SuccessOnAll:
if all([c.status == common.Status.SUCCESS for c in self.children]):
new_status = common.Status.SUCCESS
self.current_child = self.children[-1]
elif type(self.policy) is common.ParallelPolicy.SuccessOnOne:
successful = [child for child in self.children if child.status == common.Status.SUCCESS]
if successful:
new_status = common.Status.SUCCESS
self.current_child = successful[-1]
elif type(self.policy) is common.ParallelPolicy.SuccessOnSelected:
if all([c.status == common.Status.SUCCESS for c in self.policy.children]):
new_status = common.Status.SUCCESS
self.current_child = self.policy.children[-1]
else:
raise RuntimeError("this parallel has been configured with an unrecognised policy [{}]".format(type(self.policy)))
# this parallel may have children that are still running
# so if the parallel itself has reached a final status, then
# these running children need to be terminated so they don't dangle
if new_status != common.Status.RUNNING:
self.stop(new_status)
self.status = new_status
yield self
[docs] def stop(self, new_status: common.Status=common.Status.INVALID):
"""
For interrupts or any of the termination conditions, ensure that any
running children are stopped.
Args:
new_status : the composite is transitioning to this new status
"""
# clean up dangling (running) children
for child in self.children:
if child.status == common.Status.RUNNING:
# interrupt it exactly as if it was interrupted by a higher priority
child.stop(common.Status.INVALID)
# only nec. thing here is to make sure the status gets set to INVALID if
# it was a higher priority interrupt (new_status == INVALID)
Composite.stop(self, new_status)
[docs] def validate_policy_configuration(self):
"""
Policy configuration can be invalid if:
* Policy is SuccessOnSelected and no behaviours have been specified
* Policy is SuccessOnSelected and behaviours that are not children exist
Raises:
RuntimeError: if policy configuration was invalid
"""
if type(self.policy) is common.ParallelPolicy.SuccessOnSelected:
if not self.policy.children:
error_message = ("policy SuccessOnSelected requires a non-empty "
"selection of children [{}]".format(self.name))
self.logger.error(error_message)
raise RuntimeError(error_message)
missing_children_names = [child.name for child in self.policy.children if child not in self.children]
if missing_children_names:
error_message = ("policy SuccessOnSelected has selected behaviours that are "
"not children of this parallel {}[{}]""".format(missing_children_names, self.name))
self.logger.error(error_message)
raise RuntimeError(error_message)