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skywriter - python to javascript

  • Just bought a skywriter to control my mirror based on swipes and presses. (

    It comes with a python library:

    What I would like to achieve is that a certain div comes to the page when I make a “up” gesture. Or when I swipe left, that the entire page is switched to another profile.

    What is the best starting point to control javascript in a webpage thru python?

  • Moderator

    @kclemen If you want an example of how to put together python and a module, you can have a look at this. It uses a python backend for face recognition. I think you could use a similar approach to “listen” for flicks.

  • Thanks for your reply. First glance at the link, seems to be rather difficult to implement what I want.

    Following code can be generated in py to link an action to a certain “gesture”:
    if(start == “north” and finish == “south”):
    print “Volume: down”
    system(“irsend SEND_ONCE TV KEY_VOLUMEDOWN”)
    elif(start == “south” and finish == “north”):
    print “Volume: up”
    system(“irsend SEND_ONCE TV KEY_VOLUMEUP”)

    I would like to slde in a certain dev when I wave from “north” to “south”… Searches on the net results that py and javascript do not work ery well together?

  • Moderator

    @kclemen Well, you can try googling for node.js (which is programmed in javascript) and python, and the answer will be quite different.

    If you want to program this module, you will need (at least) 3 components (I will demonstrate how it works in the facial recognition example):

    • the module in the browser:
      this will listen for events send from node_helper.js, for example see this function. In the example, it broadcasts this event to all modules (here), and then catches that notification again (here) to show all modules with a certain class

    • the node_helper.js:
      this is what will be calling your python code in the backend, for example in this line the python module is started, and then listens for events here

    • your python code:
      not much here you need, most of the code would look like your example, except the communication to node from this line

    Hope this helps to get you started.

  • @Jopyth Thanks for your wonderful reply. Will take a look at it as soon the skywriter is delivered.

  • ok, first steps are being taken…

  • fixed it…

  • I’ve got following error:

    SyntaxError: Unexpected token g in JSON at position 0
    at PythonShell.asJson (/home/pi/MagicMirror/modules/MMM-skywriter/node_modules/python-shell/index.js:142:21)
    at /home/pi/MagicMirror/modules/MMM-skywriter/node_modules/python-shell/index.js:232:35
    at Array.forEach (native)
    at PythonShell.receive (/home/pi/MagicMirror/modules/MMM-skywriter/node_modules/python-shell/index.js:231:11)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:176:18)
    at Socket.Readable.push (_stream_readable.js:134:10)
    at Pipe.onread (net.js:543:20)

    Here is the script:
    `#!/usr/bin/env python
    import sys
    import json
    import time
    import signal
    import skywriter

    some_value = 5000

    last_airwheel = 0
    delay = 5000

    def to_node(type, message):
    # convert to json and print (node helper will read from stdout)
    print(json.dumps({type: message}))
    except Exception:
    # stdout has to be flushed manually to prevent delays in the node helper communication

    to_node(“status”, ‘Skywriter started…’)

    def flick(start,finish):

    #slide music player div OFF the screen
    if(start == "north" and finish == "south"):
    	print "gesture is north to south"
    	to_node("gesture", "down")
    #slide music player div ONTO the screen
    elif(start == "south" and finish == "north"):
    	print "gesture is south to north"
    	to_node("gesture", "up")
    #Next track
    elif(start == "west" and finish == "east"):
    	print "Gesture is west to east"
    	to_node("gesture", "next")
    #previous track
    elif(start == "east" and finish == "west"):
    	print "Gesture is east to west"
    	to_node("gesture", "previous")
    	# print "Invalid"

    def spinny(delta):
    global some_value
    global last_airwheel
    global delay
    some_value += delta
    if some_value < 0:
    some_value = 0
    if some_value > 10000:
    some_value = 10000
    now = int(round(time.time() * 1000))
    if(now - last_airwheel > delay):
    print(“TV & Digibox: power”)
    # system(“irsend SEND_ONCE TV KEY_POWER”)
    # system(“irsend SEND_ONCE Digibox KEY_POWER”)
    last_airwheel = now


    I do not really understand what is wrong? Anybody an idea?

  • Moderator

    @kclemen Please use three backticks (```) for markdown if you paste your code, instead of one (`). Otherwise it will not recognize it as multi line code.

    The problem are your regular print statements (e.g. print "Gesture is west to east"), these are also read by node, and they are not in the JSON format. You can comment these out, or maybe write them to a log file instead, if you want them to debug.

  • Thanks for the input. Indeed this was the mistake.

    seems I’m missing still something. Now I get following error:

    TypeError: parser.close is not a function
    at SAXStream.openf1 (/home/pi/MagicMirror/node_modules/feedme/lib/xmlfeedparser.js:107:14)
    at emitOne (events.js:96:13)
    at SAXStream.emit (events.js:188:7)
    at function) [as onopentag] (/home/pi/MagicMirror/node_modules/sax/lib/sax.js:258:17)
    at emit (/home/pi/MagicMirror/node_modules/sax/lib/sax.js:640:35)
    at emitNode (/home/pi/MagicMirror/node_modules/sax/lib/sax.js:645:5)
    at openTag (/home/pi/MagicMirror/node_modules/sax/lib/sax.js:841:5)
    at Object.write (/home/pi/MagicMirror/node_modules/sax/lib/sax.js:1404:13)
    at SAXStream.write (/home/pi/MagicMirror/node_modules/sax/lib/sax.js:239:18)
    at yoshi.write (/home/pi/MagicMirror/node_modules/feedme/lib/feedme.js:41:14)

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