[Tutor] Let imported module access calling program

[Michael Langford]

The following is a pretty normal control loop for robot control (or other
embedded devices). There are probably some syntactical errors as I'm writing
this without a working python interpreter available at this second, but it
should give you the correct gist to do what you said you were trying to do.

You may want something like:
#robotcontrol.py
import time

class OperationalStep(object):
   def __init__(self,func,interval=0):
         self.func = func
         self.interval = interval
         self.lastRun = getTime()

   def run():
        """If the step hasn't been run recently enough, do so"""
          if self.interval + self.lastRun < getTime():
              self.func()
              self.lastRun = getTime()

def unknownEvent():
  print( "This is an undefined event code" )

events = collections.defaultdict(unknownEvent)

def getTime():
   """returns time"""
  return time.clock()

def registerEventHandler(eventCode,handler):
   """When event eventCode is seen, run handler"""
   global events
   events[eventCode] = handler

def registerOperationalStep(step,delayAtLeast=0):
   """Registers a step that will be taken in the program no more often than
delayAtLeast often"""
   global tasks
   t = OperationalStep(step,delayAtLeast)
   tasks.append(t)

eventQueue = []
def addEvent(ev):
   global eventQueue
   eventQueue.append(ev)

def robotLoop():
  """runs each task, handling events as possible"""
   global eventQueue,tasks
   while True:
      for task in tasks:
          #process events
          for ev in eventQueue:
              events[ev]()

          #run next task
          task.run()


All of this would be put in its own module, say robotcontrol, that would
then be used thusly in a complete separate file:

#myrobot.py
import robotcontrol
from madeupRobotApi import *
from time import sleep


def checkBump():
   """Checks to see if the robot bump bar is pushed in"""
   if bump.pressed():
     robotcontrol.addEvent(BUMP_EVENT)

def handleSonarData():
   """gets data from the sonar"""
   data = sonar.read()
   print (data)

def handleCoreMeltdown():
    """turns off the core"""
    powercore.off()

def turnLeft():
   ""turns the robot 90 degrees left"
   lwheels.run(-10)
   rwheels.run(10)
   sleep(10)
   lwheels.run(0)
   rwheels.run(0)
   checkBump()

def turnRight():
   ""turns the robot 90 degrees right"
   lwheels.run(10)
   rwheels.run(-10)
   sleep(10)
   lwheels.run(0)
   rwheels.run(0)
   checkBump()

def goForward(speed=10,t=10):
  """goes forward at speed for time t"""
  lwheels.run(speed)
  rwheels.run(speed)
  sleep(t)
  lwheels.run(0)
  rwheels.run(0)
  checkBump()

def goForwardALittle()
  goForward(10,1)
  checkBump()

def checkSensors()
  if sonar.ready():
    robotcontrol.addEvent(SONAR_EVENT)
  if core.tooHot():
    robotcontrol.addEvent(OHNO_EVENT)

direction = "RIGHT"

def decideNewDirection():
   global direction
   if sonar.data == "heavy":
     direction = "LEFT"
   else:
     direction = "RIGHT"

def handleBump()
   """back up upon bump"""
   if bump.pressed():
     goForward(speed=-10,t=10)

def turn():
   """turns the direction specified in direction"""
   global direction
   if direction == "LEFT":
     turnLeft()
   else:
     turnRight()


def robotSetup():
   """sets all the event handlers and defines the operational program"""

   #these will happen as things generate events
   registerEventHandler(SONAR_EVENT,handleSonarData)
   registerEventHandler(OHNO_EVENT,handleCoreMeltdown)
   registerEventHandler(BUMP_EVENT,handleBump)

   #robot control scheme
   registerOperationalStep(checkSensors,10)
   registerOperationalStep(decideNewDirection)
   registerOperationalStep(turn)
   registerOperationalStep(goForwardALittle)
   registerOperationalStep(decideNewDirection)
   registerOperationalStep(turn)


if "__name__"==__main__:
  robotSetup()
  robotcontrol.robotLoop()

-- 
Michael Langford
404-386-0495
http://www.RowdyLabs.com
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