AtacamaLargeMillimeterArray ACS Training Developing Python Clients

NRAO - Socorro, July 2004ACS Training2 Python’s Pros Good stability Faster start-up time than Java Execution time usually sufficient, although not comparable to C++ Fastest development time Fewer lines of code, easy to understand if not too complex Good for asynchronous, distributed testing Ideal to allow users (astronomers) to control program behavior through scripts

NRAO - Socorro, July 2004ACS Training3 Python’s Cons No compile-time checking: code inconsistencies only discovered at run-time in forms of software errors Therefore not well suited for production software that has a large code base and gets maintained by different developers Free tool support not as good as for Java (profilers, remote debugging, IDEs, …)

NRAO - Socorro, July 2004ACS Training4 What’s Available in Python? If it’s been implemented in the ACS C++ or Java APIs chances are it also exists in Python or no one has asked for it yet. Only major thing missing is XML support in the form of “helper” classes.

NRAO - Socorro, July 2004ACS Training5 Very Simple Example from Acspy.Clients.SimpleClient import PySimpleClient simpleClient = PySimpleClient() #Make an instance of the PySimpleClient remoteComponent="MOUNT2_LOOP" try: mount = simpleClient.getComponent(remoteComponent) actAzProperty = mount._get_actAz() #Get the actAz property (azm, compl) = actAzProperty.get_sync() #Get the value of the property print "MOUNT actual azimuth: ", azm simpleClient.releaseComponent(remoteComponent) except Exception, e: print "Sorry, maybe there was no",remoteComponent,"object" print "The exception was:", e simpleClient.disconnect()

NRAO - Socorro, July 2004ACS Training6 Callback Example from Acspy.Clients.SimpleClient import PySimpleClient import ACS, ACS__POA # Import the Python CORBA stubs for BACI from time import sleep class MyMonitor(ACS__POA.CBdouble): '''This class defines method(s) that will be invoked asynchronously by the mount device''' # def __init__ (self, propName = None): if propName != None: self.propName = propName else: self.propName = "NoName" #

NRAO - Socorro, July 2004ACS Training7 Callback Example (continued) def working (self, value, completion, desc): ''' Method that does all the real work. Parameters: value = the double we are interested in completion = completion structure desc = callback struct description ''' print "Working: ", str(self.propName), " is ", str(value) # def done (self, value, completion, desc): ''' Invoked just before a monitor is destroyed. Parameters: value = the final value of the double we are interested in completion = completion structure desc = callback struct description ''' print "Done: ", str(self.propName), " is ", str(value)

NRAO - Socorro, July 2004ACS Training8 Callback Example (continued) def negotiate (self, time_to_transmit, desc): '''For simplicities sake, we always return true. ''' return TRUE # simpleClient = PySimpleClient() try: mount = simpleClient.getComponent("MOUNT2_LOOP") actAzProperty = mount._get_actAz() #Get the actAz property cbMon = MyMonitor("actAz") #Create a callback monitor for actAz cbMonServant = cbMon._this() #Activate the callback monitor desc = ACS.CBDescIn(0L, 0L, 0L) #Create the real monitor actMon = actAzProperty.create_monitor(cbMonServant, desc) actMon.set_timer_trigger( ) #Working method once per sec. sleep(10) #Destroy the monitor after ten seconds actMon.destroy()

NRAO - Socorro, July 2004ACS Training9 Callback Example (continued) # Release the component simpleClient.releaseComponent("MOUNT2_LOOP") except Exception, e: print "Sorry, I expected there to be a Mount in the system and" print "there isn't." print "The exception was:", e simpleClient.disconnect()

NRAO - Socorro, July 2004ACS Training10 What methods does PySimpleClient have? Every Python Container Service method is available in Python!!! See the Pydoc documentation for the ContainerServicesContainerServices class.

NRAO - Socorro, July 2004ACS Training11 Python-related Makefile Targets PY_SCRIPTS - Specifies Python scripts without the.py extension that will be installed into $INTROOT/bin. PY_MODULES – Specifies Python modules with the.py extension that will be installed into $INTROOT/lib/python/site-packages. PY_PACKAGES – Specifies Python packages to be installed into $INTROOT/lib/python/site-packages. Really these are just directories containing Python scripts.

NRAO - Socorro, July 2004ACS Training12 Questions about Python Clients???

NRAO - Socorro, July 2004ACS Training13 Demo