help/en/html/tools/scripting/HowTo.shtml

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      <h1>JMRI: Scripting "How To..."</h1>
 	  <!-- Page reorganized by Jerry Grochow 2018-11-29 -->

      <p class="subtitle">Some hints and examples on how to do basic operations in scripts</p>
      
      <p>NOTE REGARDING CODE EXAMPLES: The Python language provides alternative ways of addressing objects and methods;  
       examples may use one or the other syntax, as: </p>
		
		<pre>
      m = memories.provideMemory("IMXXX")
      m.value = "Anything"
        </pre>
        <pre>
      memories.provideMemory("IMYYY").setValue("Anything else")
 		</pre>
      
      <p>No assignment operator (=) is necessary in the second example as the "set" method does that work. Use whichever syntax you prefer, 
		although it is a good practice to be consistent.</p>
	  
      <ul>
	  <li><a href="#running">How do I run a saved script?</a></li>
      <li><a href="#varnaming">How should I name variables in JMRI scripts?</a></li>
	  <li><a href="#objects">How do I reference existing or create new JMRI objects (sensors, memories, etc.) in a script?</a></li>
      <li><a href="#chars">How do I use non ISO 8859-1 characters in user objects and aspects?</a></li>
	  <li><a href="#slotmon"> How do I print the slot monitor data?</a></li>
      <li>Waiting for things to change: 
        <ul>
          <li><a href="#priority">How can I limit the priority of a script?</a></li>
          <li><a href="#several">How do I wait for something(s) to change on my layout?</a></li>
          <li><a href="#multturnouts">How do I "listen" to a Turnout or Sensor?</a></li>
        </ul></li>
      <li>Doing useful things in scripts:
        <ul>
          <li><a href="#timestamp">How do I time stamp an output message in my script?</a></li>
          <li><a href="#sound">How can I get a script to play a sound?</a></li>
          <li><a href="#runwarrant">How can I run a warrant within a script?</a></li>
          <li><a href="#setroute">How do I set a route from within a script?</a></li>
        </ul></li>
      <li>Communicating with other windows, scripts, panels, files:
        <ul>
          <li><a href="#panelload">How do I load a panel file from within a script?</a></li>
          <li><a href="#windows">How do I access the JMRI application windows?</a></li>
          <li><a href="#invoke">How do I invoke another script file from a script?</a></li>
          <li><a href="#communicate">How do I communicate between scripts?</a></li>
          <li><a href="#preferences">How do I find a file in the preferences directory?</a></li>
        </ul></li>  
      </ul>
      
	  <p>See the <a href="Examples.shtml">examples page</a> for many sample scripts. Also,
        the <a href="Start.shtml">introductory page</a> shows some
        of the basic commands.</p>
	  <p>See also <a href="Python.shtml">Python/Jython Language</a> for general FAQ about the language.</p>
	  <p>See also <a href="WhatWhere.shtml">Jython Scripting "What... Where"</a> for other interesting tidbits.</p>

<!-- = = = = = = = = = = = = The How To's = = = = = = = = = = = = = = = = = -->	 
     
    <h2><a id="running">How do I run a saved script?</a></h2>
	  
	  <div class="para">
	  
	  <p>From the PanelPro main screen, click on "Panels" in the top menu. Or, from the DecoderPro main screen,
	  click on "Actions" in the top menu. Select "Run Script..." from the dropdown.</p>

      <p>The directory set up in Preferences (which you can change) will appear and you can select a script to run.  
	  YOu can also navigate to any other directory that contains stored scripts.  [On PCs, Jython script files have
	  a ".py" suffix standing for Python.]</p>
      
        <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>
      </div>
      
  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
	<h2><a id="varnaming">How should I name variables in JMRI scripts?</a></h2>

      <div class="para">
      
        <p>Short answer: you can name them any way you like!</p>
		
		<p>In many of the sample files, turnouts are referred to by
        names like "to12", signals by names like "si21", and
        sensors by names like "bo45". These conventions grew out of
        how some older code was written, and they can make the code
        clearer. But they are in no way required; the program
        doesn't care what you call variables.</p>

        <p>For example, "self.to12" is just the name of a variable.
        You can call it anything you want, e.g.
        self.MyBigFatNameForTheLeftTurnout</p>

        <p>The "self" part makes it completely local; "self" refers
        to "an object of the particular class I'm defining right
        now". Alternately, you can define a global variable, but
        that's not recommended. If you have multiple scripts
        running (and you can have as many as you'd like; we
        recommend that you put each signal head in a separate one),
        the variables can get confused if you use the same variable
        name to mean too different things. Using "self" like this
        one does makes sure that doesn't happen.</p>

        <p>Note that turnouts, etc, do have "System Names" that
        look like "LT12". You'll see those occasionally, but that's
        something different from the variable names in a script
        file.</p>
     
    <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>     
      </div>

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	<h2><a id="objects"> How do I reference existing or create new JMRI objects (sensors, memories, etc.) in a script?</a></h2>
		<!-- Section created by Jerry Grochow 2018-10-18, added info from posts to jmriusers@groups.io by Cliff Anderson on 2019-04-23
        and Dave Sand on 2019-09-05 -->
		
	  <div class="para">
		
      <p>All of the JMRI input and output objects listed in <a href="../../../../../help/en/html/tools/index.shtml">
      Common Tools</a>, such as sensors, memories, lights, signals, reporters, etc., can be accessed or new ones created 
      within a script. A simple line of code typed into the Script Entry window is all it takes to create an object:</p>
		
		<pre>
    a=memories.provideMemory("IM" + "XXX")
    b=sensors.provideSensor("IS" + "XXX")
		</pre>
		
      <p>Using the "provide" method for a specific type of input or output either creates a new object
      with the system name specified (IMXXX or ISXXX in these examples) or finds a reference to an existing
      object. These lines can also be included in scripts that are saved and then run.</p>
      
      <p>Using the "get" method, on the other hand, will find an existing object but will not create a new one.
      If your goal is to only find existing objects, you could use code like the following, where SomeSensorName
      is a variable with either a system name or a user name (see below):</p>
      
      <pre>
    c = sensors.getSensor(SomeSensorName)
    if c is None:
       print SomeSensorName," does not exist"
      </pre>
        
      <p>Once a reference is established, variables within an object can be set using statements like:</p>
		
		<pre>
    a.userName = "My memory 1"
    b.userName = "My Sensor 1 at East Yard"
    a.value = "Something I want to save"
    b.state = ACTIVE
		</pre>
		
  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  

	<h2><a id="chars">How do I use non ISO 8859-1 characters in user objects and aspects?</a></h2>
		
        <p>User Names of JMRI Object and Signal Aspects may include non ISO&nbsp;8859-1
		characters. You need to decode them properly to use these names in jython scripts.
		All strings that contain non ISO&nbsp;8859-1 characters must be decoded
		by the <b>.decode ("UTF-8")</b> method.</p>
		
		<p>Example: Distant signal of the Entry signal of the Czechoslovak State Railways 
		<a href="../../../../../xml/signals/CSD-1962-zakladni/appearance-entry_distant.xml">JMRI "&#268;SD 1962 z&#225;kladn&#237; n&#225;v&#283;stidla: P&#345;edv&#283;sti" Appearance Table</a>
		according to the rules is called <b>P&#345;L</b>. 
		The signal mast will display two aspects:  Clear &ndash; <b>Volno</b> and  
		Caution &ndash; <b>V&#253;straha</b>.</p>
		
		<p>In the table of Signal masts is distant signal mast with LocoNet DCC address 100
		with system name <b>LF$dsm:CSD-1962-zakladni:entry_distant(100)</b>.</p>
		
		<p>In the script, the signal mast and its aspects will work as follows:</p>
		
		<p>Window Script Entry:</p>
		
		<pre>
    mastDistantUserName = "P&#345;L".decode("UTF-8")
    aspectClear = "Volno"
    aspectCaution = "V&#253;straha".decode("UTF-8")
    
    mastDistant = masts.getSignalMast(mastDistantUserName)
    print "System Name:    ", mastDistant.getSystemName()
    print "User Name:      ", mastDistant.getUserName()
    
    print "aspect default: ", mastDistant.getAspect()
    
    mastDistant.setAspect(aspectClear)
    print "aspect Clear:   ", mastDistant.getAspect()
    
    mastDistant.setAspect(aspectCaution)
    print "aspect Caution: ", mastDistant.getAspect()
		</pre>
		
		
		<p>Window Script Output:</p>
		
		<pre>
    System Name:     LF$dsm:CSD-1962-zakladni:entry_distant(100)
    User Name:       P&#345;L
    aspect default:  None
    aspect Clear:    Volno
    aspect Caution:  V&#253;straha
		</pre>
		
		
            <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>
		</div>
        
  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
    <h2><a id="slotmon">How do I print slot monitor data?</a></h2>
	  
	  <div class="para">
	  <!-- Section created by Jerry Grochow 2019-10-14 based on post to jmriusers@groups.io by Bob Jacobsen 2019-10-09 -->
      
	  <p>The slot table keeps track of locomotives and consists controlled by JMRI.  To print the contents, 
      extract the data line by line and send to the printer.  Here is an example using the LocoNet slot table:</p>

      <pre>
    myLocoNetConnection = jmri.InstanceManager.getList(jmri.jmrix.loconet.LocoNetSystemConnectionMemo).get(0);
    slotManager = myLocoNetConnection.getSlotManager()
    for i in range(0, 127):
       print slotManager.slot(i).slotStatus
      </pre>
   
      <p>SystemConnectionMemo is available for many types of DCC communication systems.  See 
      <a href="https://www.jmri.org/JavaDoc/doc/jmri/jmrix/SystemConnectionMemo.html" target="_blank">
      JavaDocs </a>for more information.</p>
   
      <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>
      </div>
      

<!-- = = = = = = = = = = = = = = = Waiting for things to change = = = = = = = = = = = = = = = = = -->	 	
           
    <h2><a id="priority">How can I limit the priority of a script?</a></h2>

      <div class="para">
      
        <p>If the script runs a loop that's supposed to update
        something, it can't be written to run continuously or else
        it will just suck up as much computer time as it can.
        Rather, it should wait.</p>

        <p>The best thing to do is to wait for something to change.
        For example, if your script looks at some sensors to decide
        what to do, wait for one of those sensors to change (see
        <a href="#multturnouts">below</a> and the sample scripts for examples)</p>

        <p>Simpler, but not as efficient, is to just wait for a
        little while before checking again. For example</p>
        
    <pre>
    waitMsec(1000)
    </pre> 
    
        causes an automaton or Siglet script to wait for 1000 milliseconds (one second) before continuing.

        <p>For just a simple script, something that doesn't use the
        Automat or Siglet classes, you can sleep by doing</p>
     
     <pre>
    from time import sleep
    sleep(10)
    </pre>

      <p>The first line defines the "sleep" routine, and only needs to
      be done once. The second line then sleeps for 10 seconds. Note that
      the accuracy of this method is not as good as using one of the
      special classes.</p>

          <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>
      </div>
	    
  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
    <h2><a id="several">How do I wait for something(s) to change on my layout?</a></h2>

      <div class="para">
        <p>If your script is based on a Siglet or <a href=
        "https://jmri.org/JavaDoc/doc/jmri/jmrit/automat/AbstractAutomaton.html" target="_blank">
        AbstractAutomaton</a> class (e.g. if you're writing a
        "handle" routine" - <a href="WhatWhere.shtml#siglet-automaton" target="_blank">see What...Where page for more info on these classes</a>), 
        there's a general "<a href=
        "https://jmri.org/JavaDoc/doc/jmri/jmrit/automat/AbstractAutomaton.html#waitChange-jmri.NamedBean:A-" target="_blank">waitChange</a>"
        routine which waits for any of several sensors to change
        before returning to you. Note that more than one may change
        at the same time, so you can't assume that just one has a
        different value! And you'll then have to check whether
        they've become some particular state. It's written as:</p>
        
     <pre>
    self.waitChange([self.sensorA, self.sensorB, self.sensorC])
    </pre>
    
        where you've previously defined each of those "self.sensorA" things via a line like:

    <pre>
    self.sensorA = sensors.provideSensor("21")
    </pre>

      You can then check for various combinations like:
     <pre>
   if self.sensorA.knownState == ACTIVE :
        print "The plane! The plane!"
   elif self.sensorB.knownState == INACTIVE :
        print "Would you believe a really fast bird?"
   else
        print "Nothing to see here, move along..."
    </pre>
    You can also wait for any changes in objects of multiple types:
    <pre>
    self.waitChange([self.sensorA, self.turnoutB, self.signalC])
    </pre>

    Finally, you can specify the maximum time to wait before continuing even though nothing has changed:
    <pre>
    self.waitChange([self.sensorA, self.sensorB, self.sensorC], 5000)
    </pre>
    
    will wait a maximum of 5000 milliseconds, e.g. 5 seconds. If nothing has changed,
    the script will continue anyway.
      
          <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>
      </div>

  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
    <h2><a id="multturnouts">How do I "listen" to a Turnout or Sensor?</a></h2>

      <div class="para">
      
        <p>JMRI objects (Turnouts, Sensors, etc) can have "Listeners"
        attached to them. These are then notified when the status
        of the object changes. If you're using the Automat or
        Siglet classes, you don't need to use this capability;
        those classes handle all the creationg and registering of
        listeners. But if you want to do something special, you may
        need to use that capability.</p>

        <p>A single routine can listen to one or more Turnout,
        Sensor, etc.</p>

        <p>If you retain a reference to your listener object, you
        can attach it to more than one object:</p>
        
     <pre>
    m = MyListener()
    turnouts.provideTurnout("12").addPropertyChangeListener(m)
    turnouts.provideTurnout("13").addPropertyChangeListener(m)
    turnouts.provideTurnout("14").addPropertyChangeListener(m)
    </pre>

        <p>But how does the listener know what changed?</p>

        <p>A listener routine looks like this:</p>
        
     <pre>
class MyListener(java.beans.PropertyChangeListener):
  def propertyChange(self, event):
    print "change",event.propertyName
    print "from", event.oldValue, "to", event.newValue
    print "source systemName", event.source.systemName
    print "source userName", event.source.userName
    </pre>

        <p>When the listener is called, it's given an object
        (called event above) that contains the name of the property
        that changed, plus the old and new values of that
        property.</p>

        <p>You can also get a reference to the original object that
        changed via "name", and then do whatever you'd like through
        that. In the example above, you can retrieve the
        systemName, userName (or even other types of status).</p>

    <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>
    </div>

      
<!-- = = = = = = = = = = = = = = = = = Doing interesting things = = = = = = = = = = = = = = = = = -->	 	
      
    <h2><a id="timestamp">How do I time stamp an output message in my script?</a></h2>
    <!-- From Dave Sand 11/21/2018 -->
      <div class="para">
        
        <p>Import the "time" library and then it is easy:</p>
        
    <pre>
    import time
    .
    .
    .
    print time.strftime("%Y-%m-%d %H:%M:%S"), "Your message or variables here"
     </pre>        
    
    <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>

    </div>
    
  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
    <h2><a id="sound">How can I get a script to play a sound?</a></h2>
		
        <div class="para">
        
		<p>The
        jython/SampleSound.py file shows how to play a sound within
        a script. Briefly, you load a sound into a variable ("snd"
        in this case), then call "play()" to play it once, etc. </p>

        <p>Note that if more than one sound is playing at a time,
        the program combines them as best it can. Generally, it
        does a pretty good job.</p>

        <p>You can combine the play() call with other logic to play
        a sound when a Sensor changes, etc. Ron McKinnon provided
        an example of doing this. It plays a railroad crossing bell
        when the sensor goes active.</p>
        
    <pre>
# It listens for changes to a sensor,
# and then plays a sound file when sensor active

import jarray
import jmri

# create the sound object by loading a file
snd = jmri.jmrit.Sound("resources/sounds/Crossing.wav")

class SensndExample(jmri.jmrit.automat.Siglet) :

        # Modify this to define all of your turnouts, sensors and 
        # signal heads.
        def defineIO(self):
                
                # get the sensor 
                self.Sen1Sensor = sensors.provideSensor("473")
                                
                 # Register the inputs so setOutput will be called when needed.
                 self.setInputs(jarray.array([self.Sen1Sensor], jmri.NamedBean))

                return

        # setOutput is called when one of the inputs changes, and is
        # responsible for setting the correct output
        #
        # Modify this to do your calculation.
        def setOutput(self):
                                
                if self.Sen1Sensor.knownState==ACTIVE:
                        snd.play()

                return
        
# end of class definition

# start one of these up
SensndExample().start()
    </pre>

    <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>

    </div>
    
    
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  <h2><a id="runwarrant">How can I run a warrant from within a script?</a></h2>
  	  <!-- Section created by Jerry Grochow 2019-10-14 based on post to jmriusers@groups.io by Dave Sand 2019-07-11 -->

  <div class="para">
  
    <p>A Warrant in JMRI is a collection of information sufficient to run an automated train.  
    See <a href="../../../../../help/en/package/jmri/jmrit/logix/Warrant.shtml" target="_blank">
    the section on setting up warrants here.</a>  Get a reference to the warrant you want and run it
    by executing ("warrants" is a predefined manager reference in jython/jmri_bindings.py):</p>

    <pre>
    w = warrants.getWarrant("train 1")
    w.runWarrant(jmri.jmrit.logix.Warrant.MODE_RUN)
    </pre>  

    <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>  
  </div>

  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->

  <h2><a id="setroute">How do I set a route within a script?</a></h2>
  	  <!-- Section created by Jerry Grochow 2019-10-14 based on post to jmriusers@groups.io by Bob Jacobson 2019-01-23 -->

  <div class="para">
  
    <p>Routes are collections of Turnouts and/or Sensors whose states may be set all at once.  
    See <a href="../../../../../help/en/html/tools/Routes.shtml" target="_blank">
    the section on routes here.</a>  Get a reference to the route you want and run it
    by executing:</p>

    <pre>
    r = routes.getRoute("MyRouteName")
    r.setRoute()
        </pre>  

    <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>  
  </div>


<!-- = = = = = = = = = = = = = Communicating with other windows, scripts, panels, files = = = = = = = = -->	 	
    
    <h2><a id="panelload">How do I load a panel file from within a script?</a></h2>

      <div class="para">
    
    <pre>
    jmri.InstanceManager.getDefault(jmri.ConfigureManager).load(java.io.File("filename.xml"))
    </pre>
      
      <p>That looks for "filename.xml" in the JMRI program
      directory, which is not a good place to keep your files.
      (They tend to get lost or damaged when JMRI is updated). See
      the next question for a solution to this.</p>
      
      </div>
      
  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
    <h2><a id="windows">How do I access the JMRI application windows?</a></h2>

      <div class="para">
      
        <p>Your scripts can change the
        properties of all the main JMRI windows. They're all
        jmri.util.JmriJFrame objects, so they have all the various
        methods of a Swing JFrame. For example, this code
        snippet</p>

        <pre>
    window = jmri.util.JmriJFrame.getFrameList()[1]
    window.setLocation(java.awt.Point(0,0))
        </pre>

        <p>locates the application's main window, and sets its
        location to the upper left corner of the screen.</p>

        <p>The <code>jmri.util.JmriJFrame.getFrameList()</code>
        call in the first line returns a list of the existing
        windows. The [0] element of this list is the original
        splash screen and the [1] element is the main window; after
        that, they're the various windows in the order they are
        created. To find a particular one, you can index through
        the list checking e.g. the window's title with the
        <code>getTitle()</code> method.</p>
      
    <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>
      </div>

  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
    <h2><a id="invoke">How do I invoke another script file from a script?</a></h2>

      <div class="para">
      
    <pre>
    execfile("filename.py")
    </pre>
    
      <p>That will look for the file in the top-level JMRI
      program directory, which might now be what you want. If you
      want JMRI to search for the file in the default scripts
      directory (which you can set in preferences), use the
      slightly more complex form:</p>

    <pre>
    execfile(jmri.util.FileUtil.getExternalFilename("scripts:filename.py"))
    </pre>

      <p>The call to jmri.util.FileUtil.getExternalFilename(..) translates
      the string using JMRI's standard prefixes. The "scripts:"
      tells JMRI to search in the default scripts directory. You
      can also use other prefixes, see the <a href=
      "https://jmri.org/JavaDoc/doc/jmri/util/FileUtil.html#getExternalFilename(java.lang.String)" target="_blank">
      documentation</a>.</p>

    <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>      
      </div>

  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
    <h2><a id="communicate">How do I communicate between scripts?</a></h2>

      <div class="para">
        <p>All scripts run in the same default namespace, which means
        that a variable like "x" refers to the same location in all
        scripts. This allows you to define a procedure, for
        example, in one script, and use it elsewhere. For example,
        if a "definitions.py" file contained:</p>
        
    <pre>
    def printStatus() :
        print "x is", x
        print "y is", y
        print "z is", z
        return

    x = 0
    y = 0
    z = 0
    </pre>

       <p>Once that file has been executed, any later script can invoke
       the <code>printStatus()</code> routine in the global namespace
       whenever needed.</p>
      
        <p>You can also share variables, which allows two routines to
        share information. In the example above, the
        <code>x</code>, <code>y</code>, and <code>z</code>
        variables are available to anybody. This can lead to
        obscure bugs if two different routines are using a variable
        of the same name, without realizing that they are sharing
        data with each other. Putting your code into "classes" is a
        way to avoid that.</p>

      <p>Note that scripts imported into another script using
      <code>import</code> statements are not in the same namespace
      as other scripts and do not share variables or routines. To
      share variables from the default namespace with an imported
      script, you need to explicitly add the shared variable:</p>
      
    <pre>
    import myImport
    myImport.x = x # make x available to myImport
    </pre>

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  <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->	  
     <h2><a id="preferences">How do I find a file in the preferences directory?</a></h2>
	  
      <div class="para">
      
	  <p>You can always specify the complete pathname
      to a file, e.g. <code>C:\Documents and
      Files\mine\JMRI\filename.xml</code> or
      <code>/Users/mine/.jmri/filename.xml</code>. This is not very
      portable from computer to computer, however, and can become a
      pain to keep straight.</p>

      <p>JMRI provides a routine to convert "portable" names to
      names your computer will recognize:</p>
  
     <pre>
     fullname = jmri.util.FileUtil.getExternalFilename("preference:filename.xml")
    </pre>
    
      <p>The "<code>preference:</code>" means to look for that
      file starting in the preferences directory on the current
      computer. Other choices are "program:" and "home:", see the
      <a href=
      "https://jmri.org/JavaDoc/doc/jmri/util/FileUtil.html#getExternalFilename(java.lang.String)" target="_blank">
      documentation</a>.</p>

      <p><a href="#HowToTopOfPage">[Go to top of page]</a></p>
      </div>
      
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