How to pass id of a Tkinter Scale through command - python-2.7

Question

I am using Tkinter to create a GUI for a program I am writing that will adjust some Zigbee controlled LED lights that I have. I am using a loop to create multiple copies of a Scale that I'm going to use as a brightness slider. I manage to create the sliders properly, but I am having difficulties actually adjust the sliders correctly. Here's my code:
import simplejson as json
import requests # submits http requests
from Tkinter import *
from ttk import Frame, Button, Label, Style, Notebook
# MD5 hash from http://www.miraclesalad.com/webtools/md5.php
myhash = "d9ffaca46d5990ec39501bcdf22ee7a1"
appname = "dddd" # name content isnt relevant
num_lights = int(3)
class hueApp(Frame):
def __init__(self, parent):
Frame.__init__(self, parent)
self.parent = parent
self.initUI()
def initUI(self, *args, **kwds):
# title the app window
self.parent.title("Hue controller")
self.style = Style()
# create grid layout
self.columnconfigure(0, pad=3)
self.columnconfigure(1, pad=3)
self.columnconfigure(2, pad=3)
self.rowconfigure(0, pad=3)
self.scale=[]
self.val=[]
for i in range(num_lights):
print 'i=', i, type(i)
self.val.append(i+1)
print 'val=', self.val, type(self.val)
self.scale.append(Scale(self, from_=255, to_=0, command=lambda i=self.val: self.brightness_adj(i,light_id=i)))
print self.scale[i]
print 'i = ', i, type(i), '\n\n'
self.scale[i].set(150)
self.scale[i].grid(row=1, column=i)
if i == 2:
print '\n', self.scale, '\n'
print self.val, '\n'
self.scale[i].set(200)
self.centerWindow
self.pack()
def brightness_adj(self,light_val, light_id):
#global bri_val
print 'light_id:', light_id, type(light_id)
print 'light_val:', light_val, type(light_val)
print self.val[int(light_id)]
#print int(light_id)
bri_val = self.scale[light_id-1].get()
print bri_val
light = light_id
global huehub
huehub = "http://192.168.0.100/api/"+ myhash + "/lights/" + str(light)
#brightness_logic()
reply = requests.get(huehub)
a=json.loads(reply.text)
#print bri_val
payload = json.dumps({"bri":bri_val})
sethuehub = huehub + "/state"
reply = requests.put(sethuehub, data=payload)
def centerWindow(self):
w = 250
h = 150
sw = self.parent.winfo_screenwidth()
sh = self.parent.winfo_screenheight()
x = (sw-w)/2
y = (sh-h)/2
self.parent.geometry('%dx%d+%d+%d' % (w, h, x, y))
def main():
root=Tk() #the root window is created
app=hueApp(root) #create an instance of the application class
root.mainloop()
if __name__ == '__main__':
main()
I realize that this code probably gives an error when you try to run it. Basically my problem is that the command for each scale is only send brightness_adj the value of the scale, but I can't get it to pass through the id of the light. I was trying to do this by sending through the index of the self.scale list that it is appended into when it is created. I need to know which light is being adjusted so that I can send a new brightness to the corresponding light bulb. I hope I was clear enough. Thanks in advance!

Answer 1

I'm a little confused about what you're trying to do with the line that assigns callback functions to the scale widgets:
self.scale.append(Scale(self, from_=255, to_=0, command=lambda i=self.val: self.brightness_adj(i,light_id=i)))
since self.val is a list, and you're sending it as both the light_val and the light_id arguments, which I would think should be integers.
Possible fix:
I'm guessing that you want each callback to send a different ID to the brightness_adj function depending on which scale it's assigned to. Here's how I would fix this up:
Add this function to your hueApp class namespace:
def brightnessCallbackFactory(self, id):
return lambda light_val:self.brightness_adj(light_val, id)
Then change the callback assignment line from the above to this:
self.scale.append(Scale(self, from_=255, to_=0, command=self.brightnessCallbackFactory(i)))
That should create callback functions that retain the ID value in their internal namespace and assign them to the corresponding scale widget.