Demos

py-trees-demo-action-behaviour

Demonstrates the characteristics of a typical ‘action’ behaviour.

  • Mocks an external process and connects to it in the setup() method
  • Kickstarts new goals with the external process in the initialise() method
  • Monitors the ongoing goal status in the update() method
  • Determines RUNNING/SUCCESS pending feedback from the external process

usage: py-trees-demo-action-behaviour [-h]
_images/action.gif
class py_trees.demos.action.Action(name='Action')[source]

Bases: py_trees.behaviour.Behaviour

Connects to a subprocess to initiate a goal, and monitors the progress of that goal at each tick until the goal is completed, at which time the behaviour itself returns with success or failure (depending on success or failure of the goal itself).

This is typical of a behaviour that is connected to an external process responsible for driving hardware, conducting a plan, or a long running processing pipeline (e.g. planning/vision).

Key point - this behaviour itself should not be doing any work!

__init__(name='Action')[source]

Default construction.

initialise()[source]

Reset a counter variable.

setup(unused_timeout=15)[source]

No delayed initialisation required for this example.

terminate(new_status)[source]

Nothing to clean up in this example.

update()[source]

Increment the counter and decide upon a new status result for the behaviour.

py_trees.demos.action.main()[source]

Entry point for the demo script.

py_trees.demos.action.planning(pipe_connection)[source]

Emulates an external process which might accept long running planning jobs.

py_trees/demos/action.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
#!/usr/bin/env python
#
# License: BSD
#   https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################

"""
.. argparse::
   :module: py_trees.demos.action
   :func: command_line_argument_parser
   :prog: py-trees-demo-action-behaviour

.. image:: images/action.gif
"""

##############################################################################
# Imports
##############################################################################

import argparse
import atexit
import multiprocessing
import py_trees
import time

import py_trees.console as console

##############################################################################
# Classes
##############################################################################


def description():
    content = "Demonstrates the characteristics of a typical 'action' behaviour.\n"
    content += "\n"
    content += "* Mocks an external process and connects to it in the setup() method\n"
    content += "* Kickstarts new goals with the external process in the initialise() method\n"
    content += "* Monitors the ongoing goal status in the update() method\n"
    content += "* Determines RUNNING/SUCCESS pending feedback from the external process\n"

    if py_trees.console.has_colours:
        banner_line = console.green + "*" * 79 + "\n" + console.reset
        s = "\n"
        s += banner_line
        s += console.bold_white + "Action Behaviour".center(79) + "\n" + console.reset
        s += banner_line
        s += "\n"
        s += content
        s += "\n"
        s += banner_line
    else:
        s = content
    return s


def epilog():
    if py_trees.console.has_colours:
        return console.cyan + "And his noodly appendage reached forth to tickle the blessed...\n" + console.reset
    else:
        return None


def command_line_argument_parser():
    return argparse.ArgumentParser(description=description(),
                                   epilog=epilog(),
                                   formatter_class=argparse.RawDescriptionHelpFormatter,
                                   )


def planning(pipe_connection):
    """
    Emulates an external process which might accept long running planning jobs.
    """
    idle = True
    percentage_complete = 0
    try:
        while(True):
            if pipe_connection.poll():
                pipe_connection.recv()
                percentage_complete = 0
                idle = False
            if not idle:
                percentage_complete += 10
                pipe_connection.send([percentage_complete])
                if percentage_complete == 100:
                    idle = True
            time.sleep(0.5)
    except KeyboardInterrupt:
        pass


class Action(py_trees.behaviour.Behaviour):
    """
    Connects to a subprocess to initiate a goal, and monitors the progress
    of that goal at each tick until the goal is completed, at which time
    the behaviour itself returns with success or failure (depending on
    success or failure of the goal itself).

    This is typical of a behaviour that is connected to an external process
    responsible for driving hardware, conducting a plan, or a long running
    processing pipeline (e.g. planning/vision).

    Key point - this behaviour itself should not be doing any work!
    """
    def __init__(self, name="Action"):
        """
        Default construction.
        """
        super(Action, self).__init__(name)
        self.logger.debug("%s.__init__()" % (self.__class__.__name__))

    def setup(self, unused_timeout=15):
        """
        No delayed initialisation required for this example.
        """
        self.logger.debug("%s.setup()->connections to an external process" % (self.__class__.__name__))
        self.parent_connection, self.child_connection = multiprocessing.Pipe()
        self.planning = multiprocessing.Process(target=planning, args=(self.child_connection,))
        atexit.register(self.planning.terminate)
        self.planning.start()
        return True

    def initialise(self):
        """
        Reset a counter variable.
        """
        self.logger.debug("%s.initialise()->sending new goal" % (self.__class__.__name__))
        self.parent_connection.send(['new goal'])
        self.percentage_completion = 0

    def update(self):
        """
        Increment the counter and decide upon a new status result for the behaviour.
        """
        new_status = py_trees.Status.RUNNING
        if self.parent_connection.poll():
            self.percentage_completion = self.parent_connection.recv().pop()
            if self.percentage_completion == 100:
                new_status = py_trees.Status.SUCCESS
        if new_status == py_trees.Status.SUCCESS:
            self.feedback_message = "Processing finished"
            self.logger.debug("%s.update()[%s->%s][%s]" % (self.__class__.__name__, self.status, new_status, self.feedback_message))
        else:
            self.feedback_message = "{0}%".format(self.percentage_completion)
            self.logger.debug("%s.update()[%s][%s]" % (self.__class__.__name__, self.status, self.feedback_message))
        return new_status

    def terminate(self, new_status):
        """
        Nothing to clean up in this example.
        """
        self.logger.debug("%s.terminate()[%s->%s]" % (self.__class__.__name__, self.status, new_status))


##############################################################################
# Main
##############################################################################

def main():
    """
    Entry point for the demo script.
    """
    command_line_argument_parser().parse_args()

    print(description())

    py_trees.logging.level = py_trees.logging.Level.DEBUG

    action = Action()
    action.setup()
    try:
        for unused_i in range(0, 12):
            action.tick_once()
            time.sleep(0.5)
        print("\n")
    except KeyboardInterrupt:
        pass

py-trees-demo-behaviour-lifecycle

Demonstrates a typical day in the life of a behaviour.

This behaviour will count from 1 to 3 and then reset and repeat. As it does so, it logs and displays the methods as they are called - construction, setup, initialisation, ticking and termination.

usage: py-trees-demo-behaviour-lifecycle [-h]
_images/lifecycle.gif
class py_trees.demos.lifecycle.Counter(name='Counter')[source]

Bases: py_trees.behaviour.Behaviour

Simple counting behaviour that facilitates the demonstration of a behaviour in the demo behaviours lifecycle program.

  • Increments a counter from zero at each tick
  • Finishes with success if the counter reaches three
  • Resets the counter in the initialise() method.
__init__(name='Counter')[source]

Default construction.

initialise()[source]

Reset a counter variable.

setup(unused_timeout=15)[source]

No delayed initialisation required for this example.

terminate(new_status)[source]

Nothing to clean up in this example.

update()[source]

Increment the counter and decide upon a new status result for the behaviour.

py_trees.demos.lifecycle.main()[source]

Entry point for the demo script.

py_trees/demos/lifecycle.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
#!/usr/bin/env python
#
# License: BSD
#   https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################

"""
.. argparse::
   :module: py_trees.demos.lifecycle
   :func: command_line_argument_parser
   :prog: py-trees-demo-behaviour-lifecycle

.. image:: images/lifecycle.gif
"""

##############################################################################
# Imports
##############################################################################

import argparse
import py_trees
import time

import py_trees.console as console

##############################################################################
# Classes
##############################################################################


def description():
    content = "Demonstrates a typical day in the life of a behaviour.\n\n"
    content += "This behaviour will count from 1 to 3 and then reset and repeat. As it does\n"
    content += "so, it logs and displays the methods as they are called - construction, setup,\n"
    content += "initialisation, ticking and termination.\n"
    if py_trees.console.has_colours:
        banner_line = console.green + "*" * 79 + "\n" + console.reset
        s = "\n"
        s += banner_line
        s += console.bold_white + "Behaviour Lifecycle".center(79) + "\n" + console.reset
        s += banner_line
        s += "\n"
        s += content
        s += "\n"
        s += banner_line
    else:
        s = content
    return s


def epilog():
    if py_trees.console.has_colours:
        return console.cyan + "And his noodly appendage reached forth to tickle the blessed...\n" + console.reset
    else:
        return None


def command_line_argument_parser():
    return argparse.ArgumentParser(description=description(),
                                   epilog=epilog(),
                                   formatter_class=argparse.RawDescriptionHelpFormatter,
                                   )


class Counter(py_trees.behaviour.Behaviour):
    """
    Simple counting behaviour that facilitates the demonstration of a behaviour in
    the demo behaviours lifecycle program.

    * Increments a counter from zero at each tick
    * Finishes with success if the counter reaches three
    * Resets the counter in the initialise() method.
    """
    def __init__(self, name="Counter"):
        """
        Default construction.
        """
        super(Counter, self).__init__(name)
        self.logger.debug("%s.__init__()" % (self.__class__.__name__))

    def setup(self, unused_timeout=15):
        """
        No delayed initialisation required for this example.
        """
        self.logger.debug("%s.setup()" % (self.__class__.__name__))
        return True

    def initialise(self):
        """
        Reset a counter variable.
        """
        self.logger.debug("%s.initialise()" % (self.__class__.__name__))
        self.counter = 0

    def update(self):
        """
        Increment the counter and decide upon a new status result for the behaviour.
        """
        self.counter += 1
        new_status = py_trees.Status.SUCCESS if self.counter == 3 else py_trees.Status.RUNNING
        if new_status == py_trees.Status.SUCCESS:
            self.feedback_message = "counting...{0} - phew, thats enough for today".format(self.counter)
        else:
            self.feedback_message = "still counting"
        self.logger.debug("%s.update()[%s->%s][%s]" % (self.__class__.__name__, self.status, new_status, self.feedback_message))
        return new_status

    def terminate(self, new_status):
        """
        Nothing to clean up in this example.
        """
        self.logger.debug("%s.terminate()[%s->%s]" % (self.__class__.__name__, self.status, new_status))


##############################################################################
# Main
##############################################################################

def main():
    """
    Entry point for the demo script.
    """
    command_line_argument_parser().parse_args()

    print(description())

    py_trees.logging.level = py_trees.logging.Level.DEBUG

    counter = Counter()
    counter.setup()
    try:
        for unused_i in range(0, 7):
            counter.tick_once()
            time.sleep(0.5)
        print("\n")
    except KeyboardInterrupt:
        print("")
        pass

py-trees-demo-blackboard

Demonstrates usage of the blackboard and related behaviours.

A sequence is populated with a default set blackboard variable behaviour, a custom write to blackboard behaviour that writes a more complicated structure, and finally a default check blackboard variable beheaviour that looks for the first variable.

usage: py-trees-demo-blackboard [-h] [-r]

Named Arguments

-r, --render

render dot tree to file

Default: False
digraph sequence { graph [fontname="times-roman"]; node [fontname="times-roman"]; edge [fontname="times-roman"]; Sequence [fillcolor=orange, fontcolor=black, fontsize=11, shape=box, style=filled]; "Set Foo" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> "Set Foo"; Writer [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> Writer; "Check Foo" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> "Check Foo"; }
_images/blackboard.gif
class py_trees.demos.blackboard.BlackboardWriter(name='Writer')[source]

Bases: py_trees.behaviour.Behaviour

Custom writer that submits a more complicated variable to the blackboard.

__init__(name='Writer')[source]

Initialize self. See help(type(self)) for accurate signature.

update()[source]

Write a dictionary to the blackboard and return SUCCESS.

py_trees.demos.blackboard.main()[source]

Entry point for the demo script.

py_trees/demos/blackboard.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
#!/usr/bin/env python
#
# License: BSD
#   https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################

"""
.. argparse::
   :module: py_trees.demos.blackboard
   :func: command_line_argument_parser
   :prog: py-trees-demo-blackboard

.. graphviz:: dot/demo-blackboard.dot

.. image:: images/blackboard.gif
"""

##############################################################################
# Imports
##############################################################################

import argparse
import py_trees
import sys

import py_trees.console as console

##############################################################################
# Classes
##############################################################################


def description():
    content = "Demonstrates usage of the blackboard and related behaviours.\n"
    content += "\n"
    content += "A sequence is populated with a default set blackboard variable\n"
    content += "behaviour, a custom write to blackboard behaviour that writes\n"
    content += "a more complicated structure, and finally a default check\n"
    content += "blackboard variable beheaviour that looks for the first variable.\n"

    if py_trees.console.has_colours:
        banner_line = console.green + "*" * 79 + "\n" + console.reset
        s = "\n"
        s += banner_line
        s += console.bold_white + "Blackboard".center(79) + "\n" + console.reset
        s += banner_line
        s += "\n"
        s += content
        s += "\n"
        s += banner_line
    else:
        s = content
    return s


def epilog():
    if py_trees.console.has_colours:
        return console.cyan + "And his noodly appendage reached forth to tickle the blessed...\n" + console.reset
    else:
        return None


def command_line_argument_parser():
    parser = argparse.ArgumentParser(description=description(),
                                     epilog=epilog(),
                                     formatter_class=argparse.RawDescriptionHelpFormatter,
                                     )
    parser.add_argument('-r', '--render', action='store_true', help='render dot tree to file')
    return parser


class BlackboardWriter(py_trees.behaviour.Behaviour):
    """
    Custom writer that submits a more complicated variable to the blackboard.
    """
    def __init__(self, name="Writer"):
        super(BlackboardWriter, self).__init__(name)
        self.logger.debug("%s.__init__()" % (self.__class__.__name__))
        self.blackboard = py_trees.blackboard.Blackboard()

    def update(self):
        """
        Write a dictionary to the blackboard and return :data:`~py_trees.Status.SUCCESS`.
        """
        self.logger.debug("%s.update()" % (self.__class__.__name__))
        self.blackboard.spaghetti = {"type": "Gnocchi", "quantity": 2}
        return py_trees.Status.SUCCESS


def create_tree():
    root = py_trees.composites.Sequence("Sequence")
    set_blackboard_variable = py_trees.blackboard.SetBlackboardVariable(name="Set Foo", variable_name="foo", variable_value="bar")
    write_blackboard_variable = BlackboardWriter(name="Writer")
    check_blackboard_variable = py_trees.blackboard.CheckBlackboardVariable(name="Check Foo", variable_name="foo", expected_value="bar")
    root.add_children([set_blackboard_variable, write_blackboard_variable, check_blackboard_variable])
    return root


##############################################################################
# Main
##############################################################################

def main():
    """
    Entry point for the demo script.
    """
    args = command_line_argument_parser().parse_args()
    print(description())
    py_trees.logging.level = py_trees.logging.Level.DEBUG

    tree = create_tree()

    ####################
    # Rendering
    ####################
    if args.render:
        py_trees.display.render_dot_tree(tree)
        sys.exit()

    ####################
    # Execute
    ####################
    tree.setup(timeout=15)
    print("\n--------- Tick 0 ---------\n")
    tree.tick_once()
    print("\n")
    py_trees.display.print_ascii_tree(tree, show_status=True)
    print("\n")
    print(py_trees.blackboard.Blackboard())

py-trees-demo-context-switching

Demonstrates context switching with parallels and sequences.

A context switching behaviour is run in parallel with a work sequence. Switching the context occurs in the initialise() and terminate() methods of the context switching behaviour. Note that whether the sequence results in failure or success, the context switch behaviour will always call the terminate() method to restore the context. It will also call terminate() to restore the context in the event of a higher priority parent cancelling this parallel subtree.

usage: py-trees-demo-context-switching [-h] [-r]

Named Arguments

-r, --render

render dot tree to file

Default: False
digraph parallel { graph [fontname="times-roman"]; node [fontname="times-roman"]; edge [fontname="times-roman"]; Parallel [fillcolor=gold, fontcolor=black, fontsize=11, shape=note, style=filled]; Context [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Parallel -> Context; Sequence [fillcolor=orange, fontcolor=black, fontsize=11, shape=box, style=filled]; Parallel -> Sequence; "Action 1" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> "Action 1"; "Action 2" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> "Action 2"; }
_images/context_switching.gif
class py_trees.demos.context_switching.ContextSwitch(name='ContextSwitch')[source]

Bases: py_trees.behaviour.Behaviour

An example of a context switching class that sets (in initialise()) and restores a context (in terminate()). Use in parallel with a sequence/subtree that does the work while in this context.

Attention

Simply setting a pair of behaviours (set and reset context) on either end of a sequence will not suffice for context switching. In the case that one of the work behaviours in the sequence fails, the final reset context switch will never trigger.

__init__(name='ContextSwitch')[source]

Initialize self. See help(type(self)) for accurate signature.

initialise()[source]

Backup and set a new context.

terminate(new_status)[source]

Restore the context with the previously backed up context.

update()[source]

Just returns RUNNING while it waits for other activities to finish.

py_trees.demos.context_switching.main()[source]

Entry point for the demo script.

py_trees/demos/contex_switching.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
#!/usr/bin/env python
#
# License: BSD
#   https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################

"""
.. argparse::
   :module: py_trees.demos.context_switching
   :func: command_line_argument_parser
   :prog: py-trees-demo-context-switching

.. graphviz:: dot/demo-context_switching.dot

.. image:: images/context_switching.gif
"""

##############################################################################
# Imports
##############################################################################

import argparse
import py_trees
import sys
import time

import py_trees.console as console

##############################################################################
# Classes
##############################################################################


def description():
    content = "Demonstrates context switching with parallels and sequences.\n"
    content += "\n"
    content += "A context switching behaviour is run in parallel with a work sequence.\n"
    content += "Switching the context occurs in the initialise() and terminate() methods\n"
    content += "of the context switching behaviour. Note that whether the sequence results\n"
    content += "in failure or success, the context switch behaviour will always call the\n"
    content += "terminate() method to restore the context. It will also call terminate()\n"
    content += "to restore the context in the event of a higher priority parent cancelling\n"
    content += "this parallel subtree.\n"
    if py_trees.console.has_colours:
        banner_line = console.green + "*" * 79 + "\n" + console.reset
        s = "\n"
        s += banner_line
        s += console.bold_white + "Context Switching".center(79) + "\n" + console.reset
        s += banner_line
        s += "\n"
        s += content
        s += "\n"
        s += banner_line
    else:
        s = content
    return s


def epilog():
    if py_trees.console.has_colours:
        return console.cyan + "And his noodly appendage reached forth to tickle the blessed...\n" + console.reset
    else:
        return None


def command_line_argument_parser():
    parser = argparse.ArgumentParser(description=description(),
                                     epilog=epilog(),
                                     formatter_class=argparse.RawDescriptionHelpFormatter,
                                     )
    parser.add_argument('-r', '--render', action='store_true', help='render dot tree to file')
    return parser


class ContextSwitch(py_trees.behaviour.Behaviour):
    """
    An example of a context switching class that sets (in ``initialise()``)
    and restores a context (in ``terminate()``). Use in parallel with a
    sequence/subtree that does the work while in this context.

    .. attention:: Simply setting a pair of behaviours (set and reset context) on
        either end of a sequence will not suffice for context switching. In the case
        that one of the work behaviours in the sequence fails, the final reset context
        switch will never trigger.

    """
    def __init__(self, name="ContextSwitch"):
        super(ContextSwitch, self).__init__(name)
        self.feedback_message = "old context"

    def initialise(self):
        """
        Backup and set a new context.
        """
        self.logger.debug("%s.initialise()[switch context]" % (self.__class__.__name__))
        self.feedback_message = "new context"

    def update(self):
        """
        Just returns RUNNING while it waits for other activities to finish.
        """
        self.logger.debug("%s.update()[RUNNING][%s]" % (self.__class__.__name__, self.feedback_message))
        return py_trees.Status.RUNNING

    def terminate(self, new_status):
        """
        Restore the context with the previously backed up context.
        """
        self.logger.debug("%s.terminate()[%s->%s][restore context]" % (self.__class__.__name__, self.status, new_status))
        self.feedback_message = "old context"


def create_tree():
    root = py_trees.composites.Parallel(name="Parallel", policy=py_trees.common.ParallelPolicy.SUCCESS_ON_ONE)
    context_switch = ContextSwitch(name="Context")
    sequence = py_trees.composites.Sequence(name="Sequence")
    for job in ["Action 1", "Action 2"]:
        success_after_two = py_trees.behaviours.Count(name=job,
                                                      fail_until=0,
                                                      running_until=2,
                                                      success_until=10)
        sequence.add_child(success_after_two)
    root.add_child(context_switch)
    root.add_child(sequence)
    return root


##############################################################################
# Main
##############################################################################

def main():
    """
    Entry point for the demo script.
    """
    args = command_line_argument_parser().parse_args()
    print(description())
    py_trees.logging.level = py_trees.logging.Level.DEBUG

    tree = create_tree()

    ####################
    # Rendering
    ####################
    if args.render:
        py_trees.display.render_dot_tree(tree)
        sys.exit()

    ####################
    # Execute
    ####################
    tree.setup(timeout=15)
    for i in range(1, 6):
        try:
            print("\n--------- Tick {0} ---------\n".format(i))
            tree.tick_once()
            print("\n")
            py_trees.display.print_ascii_tree(tree, show_status=True)
            time.sleep(1.0)
        except KeyboardInterrupt:
            break
    print("\n")

py-trees-demo-dot-graphs

Renders a dot graph for a simple tree, with blackboxes.

usage: py-trees-demo-dot-graphs [-h]
                                [-l {all,fine_detail,detail,component,big_picture}]

Named Arguments

-l, --level

Possible choices: all, fine_detail, detail, component, big_picture

visibility level

Default: “fine_detail”
digraph demo_dot_graphs_fine_detail { graph [fontname="times-roman"]; node [fontname="times-roman"]; edge [fontname="times-roman"]; "Demo Dot Graphs fine_detail" [fillcolor=cyan, fontcolor=black, fontsize=11, shape=octagon, style=filled]; "BlackBox 1" [fillcolor=gray20, fontcolor=white, fontsize=11, shape=box, style=filled]; "Demo Dot Graphs fine_detail" -> "BlackBox 1"; Worker [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "BlackBox 1" -> Worker; "Worker*" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "BlackBox 1" -> "Worker*"; "Worker**" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "BlackBox 1" -> "Worker**"; "Blackbox 3" [fillcolor=gray20, fontcolor=dodgerblue, fontsize=11, shape=box, style=filled]; "BlackBox 1" -> "Blackbox 3"; "Worker***" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "Blackbox 3" -> "Worker***"; "Worker****" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "Blackbox 3" -> "Worker****"; "Worker*****" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "Blackbox 3" -> "Worker*****"; "Blackbox 2" [fillcolor=gray20, fontcolor=lawngreen, fontsize=11, shape=box, style=filled]; "Demo Dot Graphs fine_detail" -> "Blackbox 2"; "Worker******" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "Blackbox 2" -> "Worker******"; "Worker*******" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "Blackbox 2" -> "Worker*******"; "Worker********" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "Blackbox 2" -> "Worker********"; }
py_trees.demos.dot_graphs.main()[source]

Entry point for the demo script.

py_trees/demos/dot_graphs.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
#!/usr/bin/env python
#
# License: BSD
#   https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################

"""
.. argparse::
   :module: py_trees.demos.dot_graphs
   :func: command_line_argument_parser
   :prog: py-trees-demo-dot-graphs

.. graphviz:: dot/demo-dot-graphs.dot

"""

##############################################################################
# Imports
##############################################################################

import argparse
import subprocess
import py_trees

import py_trees.console as console

##############################################################################
# Classes
##############################################################################


def description():
    name = "py-trees-demo-dot-graphs"
    content = "Renders a dot graph for a simple tree, with blackboxes.\n"
    if py_trees.console.has_colours:
        banner_line = console.green + "*" * 79 + "\n" + console.reset
        s = "\n"
        s += banner_line
        s += console.bold_white + "Dot Graphs".center(79) + "\n" + console.reset
        s += banner_line
        s += "\n"
        s += content
        s += "\n"
        s += console.white
        s += console.bold + "    Generate Full Dot Graph" + console.reset + "\n"
        s += "\n"
        s += console.cyan + "        {0}".format(name) + console.reset + "\n"
        s += "\n"
        s += console.bold + "    With Varying Visibility Levels" + console.reset + "\n"
        s += "\n"
        s += console.cyan + "        {0}".format(name) + console.yellow + " --level=all" + console.reset + "\n"
        s += console.cyan + "        {0}".format(name) + console.yellow + " --level=detail" + console.reset + "\n"
        s += console.cyan + "        {0}".format(name) + console.yellow + " --level=component" + console.reset + "\n"
        s += console.cyan + "        {0}".format(name) + console.yellow + " --level=big_picture" + console.reset + "\n"
        s += "\n"
        s += banner_line
    else:
        s = content
    return s


def epilog():
    if py_trees.console.has_colours:
        return console.cyan + "And his noodly appendage reached forth to tickle the blessed...\n" + console.reset
    else:
        return None


def command_line_argument_parser():
    parser = argparse.ArgumentParser(description=description(),
                                     epilog=epilog(),
                                     formatter_class=argparse.RawDescriptionHelpFormatter,
                                     )
    parser.add_argument('-l', '--level', action='store',
                        default='fine_detail',
                        choices=['all', 'fine_detail', 'detail', 'component', 'big_picture'],
                        help='visibility level')
    return parser


def create_tree(level):
    root = py_trees.composites.Selector("Demo Dot Graphs %s" % level)
    first_blackbox = py_trees.composites.Sequence("BlackBox 1")
    first_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    first_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    first_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    first_blackbox.blackbox_level = py_trees.common.BlackBoxLevel.BIG_PICTURE
    second_blackbox = py_trees.composites.Sequence("Blackbox 2")
    second_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    second_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    second_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    second_blackbox.blackbox_level = py_trees.common.BlackBoxLevel.COMPONENT
    third_blackbox = py_trees.composites.Sequence("Blackbox 3")
    third_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    third_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    third_blackbox.add_child(py_trees.behaviours.Running("Worker"))
    third_blackbox.blackbox_level = py_trees.common.BlackBoxLevel.DETAIL
    root.add_child(first_blackbox)
    root.add_child(second_blackbox)
    first_blackbox.add_child(third_blackbox)
    return root


##############################################################################
# Main
##############################################################################

def main():
    """
    Entry point for the demo script.
    """
    args = command_line_argument_parser().parse_args()
    args.enum_level = py_trees.common.string_to_visibility_level(args.level)
    print(description())
    py_trees.logging.level = py_trees.logging.Level.DEBUG

    root = create_tree(args.level)
    py_trees.display.render_dot_tree(root, args.enum_level)

    if py_trees.utilities.which("xdot"):
        try:
            subprocess.call(["xdot", "demo_dot_graphs_%s.dot" % args.level])
        except KeyboardInterrupt:
            pass
    else:
        print("")
        console.logerror("No xdot viewer found, skipping display [hint: sudo apt install xdot]")
        print("")

py-trees-demo-selector

Higher priority switching and interruption in the children of a selector.

In this example the higher priority child is setup to fail initially, falling back to the continually running second child. On the third tick, the first child succeeds and cancels the hitherto running child.

usage: py-trees-demo-selector [-h] [-r]

Named Arguments

-r, --render

render dot tree to file

Default: False
digraph selector { graph [fontname="times-roman"]; node [fontname="times-roman"]; edge [fontname="times-roman"]; Selector [fillcolor=cyan, fontcolor=black, fontsize=11, shape=octagon, style=filled]; "After Two" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Selector -> "After Two"; Running [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Selector -> Running; }
_images/selector.gif
py_trees.demos.selector.main()[source]

Entry point for the demo script.

py_trees/demos/selector.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
#!/usr/bin/env python
#
# License: BSD
#   https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################

"""
.. argparse::
   :module: py_trees.demos.selector
   :func: command_line_argument_parser
   :prog: py-trees-demo-selector

.. graphviz:: dot/demo-selector.dot

.. image:: images/selector.gif

"""
##############################################################################
# Imports
##############################################################################

import argparse
import py_trees
import sys
import time

import py_trees.console as console

##############################################################################
# Classes
##############################################################################


def description():
    content = "Higher priority switching and interruption in the children of a selector.\n"
    content += "\n"
    content += "In this example the higher priority child is setup to fail initially,\n"
    content += "falling back to the continually running second child. On the third\n"
    content += "tick, the first child succeeds and cancels the hitherto running child.\n"
    if py_trees.console.has_colours:
        banner_line = console.green + "*" * 79 + "\n" + console.reset
        s = "\n"
        s += banner_line
        s += console.bold_white + "Selectors".center(79) + "\n" + console.reset
        s += banner_line
        s += "\n"
        s += content
        s += "\n"
        s += banner_line
    else:
        s = content
    return s


def epilog():
    if py_trees.console.has_colours:
        return console.cyan + "And his noodly appendage reached forth to tickle the blessed...\n" + console.reset
    else:
        return None


def command_line_argument_parser():
    parser = argparse.ArgumentParser(description=description(),
                                     epilog=epilog(),
                                     formatter_class=argparse.RawDescriptionHelpFormatter,
                                     )
    parser.add_argument('-r', '--render', action='store_true', help='render dot tree to file')
    return parser


def create_tree():
    root = py_trees.composites.Selector("Selector")
    success_after_two = py_trees.behaviours.Count(name="After Two",
                                                  fail_until=2,
                                                  running_until=2,
                                                  success_until=10)
    always_running = py_trees.behaviours.Running(name="Running")
    root.add_children([success_after_two, always_running])
    return root


##############################################################################
# Main
##############################################################################

def main():
    """
    Entry point for the demo script.
    """
    args = command_line_argument_parser().parse_args()
    print(description())
    py_trees.logging.level = py_trees.logging.Level.DEBUG

    tree = create_tree()

    ####################
    # Rendering
    ####################
    if args.render:
        py_trees.display.render_dot_tree(tree)
        sys.exit()

    ####################
    # Execute
    ####################
    tree.setup(timeout=15)
    for i in range(1, 4):
        try:
            print("\n--------- Tick {0} ---------\n".format(i))
            tree.tick_once()
            print("\n")
            py_trees.display.print_ascii_tree(tree, show_status=True)
            time.sleep(1.0)
        except KeyboardInterrupt:
            break
    print("\n")

py-trees-demo-sequence

Demonstrates sequences in action.

A sequence is populated with 2-tick jobs that are allowed to run through to completion.

usage: py-trees-demo-sequence [-h] [-r]

Named Arguments

-r, --render

render dot tree to file

Default: False
digraph sequence { graph [fontname="times-roman"]; node [fontname="times-roman"]; edge [fontname="times-roman"]; Sequence [fillcolor=orange, fontcolor=black, fontsize=11, shape=box, style=filled]; "Job 1" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> "Job 1"; "Job 2" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> "Job 2"; "Job 3" [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> "Job 3"; }
_images/sequence.gif
py_trees.demos.sequence.main()[source]

Entry point for the demo script.

py_trees/demos/sequence.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
#!/usr/bin/env python
#
# License: BSD
#   https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################

"""
.. argparse::
   :module: py_trees.demos.sequence
   :func: command_line_argument_parser
   :prog: py-trees-demo-sequence

.. graphviz:: dot/demo-sequence.dot

.. image:: images/sequence.gif
"""

##############################################################################
# Imports
##############################################################################

import argparse
import py_trees
import sys
import time

import py_trees.console as console

##############################################################################
# Classes
##############################################################################


def description():
    content = "Demonstrates sequences in action.\n\n"
    content += "A sequence is populated with 2-tick jobs that are allowed to run through to\n"
    content += "completion.\n"

    if py_trees.console.has_colours:
        banner_line = console.green + "*" * 79 + "\n" + console.reset
        s = "\n"
        s += banner_line
        s += console.bold_white + "Sequences".center(79) + "\n" + console.reset
        s += banner_line
        s += "\n"
        s += content
        s += "\n"
        s += banner_line
    else:
        s = content
    return s


def epilog():
    if py_trees.console.has_colours:
        return console.cyan + "And his noodly appendage reached forth to tickle the blessed...\n" + console.reset
    else:
        return None


def command_line_argument_parser():
    parser = argparse.ArgumentParser(description=description(),
                                     epilog=epilog(),
                                     formatter_class=argparse.RawDescriptionHelpFormatter,
                                     )
    parser.add_argument('-r', '--render', action='store_true', help='render dot tree to file')
    return parser


def create_tree():
    root = py_trees.composites.Sequence("Sequence")
    for action in ["Action 1", "Action 2", "Action 3"]:
        success_after_two = py_trees.behaviours.Count(name=action,
                                                      fail_until=0,
                                                      running_until=1,
                                                      success_until=10)
        root.add_child(success_after_two)
    return root


##############################################################################
# Main
##############################################################################

def main():
    """
    Entry point for the demo script.
    """
    args = command_line_argument_parser().parse_args()
    print(description())
    py_trees.logging.level = py_trees.logging.Level.DEBUG

    tree = create_tree()

    ####################
    # Rendering
    ####################
    if args.render:
        py_trees.display.render_dot_tree(tree)
        sys.exit()

    ####################
    # Execute
    ####################
    tree.setup(timeout=15)
    for i in range(1, 6):
        try:
            print("\n--------- Tick {0} ---------\n".format(i))
            tree.tick_once()
            print("\n")
            py_trees.display.print_ascii_tree(tree, show_status=True)
            time.sleep(1.0)
        except KeyboardInterrupt:
            break
    print("\n")

py-trees-demo-tree-stewardship

A demonstration of tree stewardship.

A slightly less trivial tree that uses a simple stdout pre-tick handler and both the debug and snapshot visitors for logging and displaying the state of the tree.

EVENTS

  • 3 : sequence switches from running to success
  • 4 : selector’s first child flicks to success once only
  • 8 : the fallback idler kicks in as everything else fails
  • 14 : the first child kicks in again, aborting a running sequence behind it

usage: py-trees-demo-tree-stewardship [-h] [-r | -i]

Named Arguments

-r, --render

render dot tree to file

Default: False

-i, --interactive
 

pause and wait for keypress at each tick

Default: False
digraph demo_tree { graph [fontname="times-roman"]; node [fontname="times-roman"]; edge [fontname="times-roman"]; "Demo Tree" [fillcolor=cyan, fontcolor=black, fontsize=11, shape=octagon, style=filled]; EveryN [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "Demo Tree" -> EveryN; Sequence [fillcolor=gray20, fontcolor=lawngreen, fontsize=11, shape=box, style=filled]; "Demo Tree" -> Sequence; Guard [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> Guard; Periodic [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> Periodic; Finisher [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; Sequence -> Finisher; Idle [fillcolor=gray, fontcolor=black, fontsize=11, shape=ellipse, style=filled]; "Demo Tree" -> Idle; }
_images/tree_stewardship.gif
py_trees.demos.stewardship.main()[source]

Entry point for the demo script.

py_trees.demos.stewardship.post_tick_handler(snapshot_visitor, behaviour_tree)[source]

Prints an ascii tree with the current snapshot status.

py_trees.demos.stewardship.pre_tick_handler(behaviour_tree)[source]

This prints a banner and will run immediately before every tick of the tree.

Parameters:behaviour_tree (BehaviourTree) – the tree custodian
py_trees/demos/stewardship.py
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
#!/usr/bin/env python
#
# License: BSD
#   https://raw.githubusercontent.com/stonier/py_trees/devel/LICENSE
#
##############################################################################
# Documentation
##############################################################################

"""
.. argparse::
   :module: py_trees.demos.stewardship
   :func: command_line_argument_parser
   :prog: py-trees-demo-tree-stewardship

.. graphviz:: dot/stewardship.dot

.. image:: images/tree_stewardship.gif
"""

##############################################################################
# Imports
##############################################################################

import argparse
import functools
import py_trees
import sys
import time

import py_trees.console as console

##############################################################################
# Classes
##############################################################################


def description(root):
    content = "A demonstration of tree stewardship.\n\n"
    content += "A slightly less trivial tree that uses a simple stdout pre-tick handler\n"
    content += "and both the debug and snapshot visitors for logging and displaying\n"
    content += "the state of the tree.\n"
    content += "\n"
    content += "EVENTS\n"
    content += "\n"
    content += " -  3 : sequence switches from running to success\n"
    content += " -  4 : selector's first child flicks to success once only\n"
    content += " -  8 : the fallback idler kicks in as everything else fails\n"
    content += " - 14 : the first child kicks in again, aborting a running sequence behind it\n"
    content += "\n"
    if py_trees.console.has_colours:
        banner_line = console.green + "*" * 79 + "\n" + console.reset
        s = "\n"
        s += banner_line
        s += console.bold_white + "Trees".center(79) + "\n" + console.reset
        s += banner_line
        s += "\n"
        s += content
        s += "\n"
        s += banner_line
    else:
        s = content
    return s


def epilog():
    if py_trees.console.has_colours:
        return console.cyan + "And his noodly appendage reached forth to tickle the blessed...\n" + console.reset
    else:
        return None


def command_line_argument_parser():
    parser = argparse.ArgumentParser(description=description(create_tree()),
                                     epilog=epilog(),
                                     formatter_class=argparse.RawDescriptionHelpFormatter,
                                     )
    group = parser.add_mutually_exclusive_group()
    group.add_argument('-r', '--render', action='store_true', help='render dot tree to file')
    group.add_argument('-i', '--interactive', action='store_true', help='pause and wait for keypress at each tick')
    return parser


def pre_tick_handler(behaviour_tree):
    """
    This prints a banner and will run immediately before every tick of the tree.

    Args:
        behaviour_tree (:class:`~py_trees.trees.BehaviourTree`): the tree custodian

    """
    print("\n--------- Run %s ---------\n" % behaviour_tree.count)


def post_tick_handler(snapshot_visitor, behaviour_tree):
    """
    Prints an ascii tree with the current snapshot status.
    """
    print("\n" + py_trees.display.ascii_tree(behaviour_tree.root,
                                             snapshot_information=snapshot_visitor))


def create_tree():
    every_n_success = py_trees.behaviours.SuccessEveryN("EveryN", 5)
    sequence = py_trees.Sequence(name="Sequence")
    guard = py_trees.behaviours.Success("Guard")
    periodic_success = py_trees.behaviours.Periodic("Periodic", 3)
    finisher = py_trees.behaviours.Success("Finisher")
    sequence.add_child(guard)
    sequence.add_child(periodic_success)
    sequence.add_child(finisher)
    sequence.blackbox_level = py_trees.common.BlackBoxLevel.COMPONENT
    idle = py_trees.behaviours.Success("Idle")
    root = py_trees.Selector(name="Demo Tree")
    root.add_child(every_n_success)
    root.add_child(sequence)
    root.add_child(idle)
    return root


##############################################################################
# Main
##############################################################################

def main():
    """
    Entry point for the demo script.
    """
    args = command_line_argument_parser().parse_args()
    py_trees.logging.level = py_trees.logging.Level.DEBUG
    tree = create_tree()
    print(description(tree))

    ####################
    # Rendering
    ####################
    if args.render:
        py_trees.display.render_dot_tree(tree)
        sys.exit()

    ####################
    # Tree Stewardship
    ####################
    behaviour_tree = py_trees.trees.BehaviourTree(tree)
    behaviour_tree.add_pre_tick_handler(pre_tick_handler)
    behaviour_tree.visitors.append(py_trees.visitors.DebugVisitor())
    snapshot_visitor = py_trees.visitors.SnapshotVisitor()
    behaviour_tree.add_post_tick_handler(functools.partial(post_tick_handler, snapshot_visitor))
    behaviour_tree.visitors.append(snapshot_visitor)
    behaviour_tree.setup(timeout=15)

    ####################
    # Tick Tock
    ####################
    if args.interactive:
        unused_result = py_trees.console.read_single_keypress()
    while True:
        try:
            behaviour_tree.tick()
            if args.interactive:
                unused_result = py_trees.console.read_single_keypress()
            else:
                time.sleep(0.5)
        except KeyboardInterrupt:
            break
    print("\n")