#!/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
[docs]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.
"""
[docs] def __init__(self, name="ContextSwitch"):
super(ContextSwitch, self).__init__(name)
self.feedback_message = "old context"
[docs] def initialise(self):
"""
Backup and set a new context.
"""
self.logger.debug("%s.initialise()[switch context]" % (self.__class__.__name__))
self.feedback_message = "new context"
[docs] 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
[docs] 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
##############################################################################
[docs]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")