title: Invalid Syntax for Assignment in Kivy File
body: <p>I've got a KV file that describes a simple popup with a few sliders that are supposed to change the R, G and B values of a color ListProperty.</p>
  
  <pre><code>Slider:
     value: root.color[0] = self.value
  Slider:
     value: root.color[1] = self.value
  Slider:
      value: root.color[2] = self.value
  </code></pre>
  
  <p>When I attempt to run the app, Python insists that my assignment for the values is invalid syntax. I've looked over the rest of the code and can't find what the problem is.</p>
  
  <p>Here's the entire KV file:</p>
  
  <pre><code>&lt;WelcomeScreen&gt;:
      AnchorLayout:
          anchor_x: 'center'
          anchor_y: 'bottom'
          Button:
              text: "Welcome!"
              size_hint: 0.1,0.1
              on_press: root.manager.current = app.screens[7] 
  
  &lt;PhoneSelection&gt;:
      BoxLayout:
          Button:
              text: "iPhone 4/4s"
              on_press: 
                  root.manager.current = app.screens[1] 
                  app.vars.phone_type = "iPhone YAYAYA"
                  self.text = str(app.vars.phone_type)
  
  &lt;PhotoEditor&gt;
      AnchorLayout:
          anchor_x: 'center'
          anchor_y: 'bottom'
          Button:
              text: 'Color'
              on_press: root.open_popup()
  
  &lt;ColorPopup&gt;
      size_hint: .5, .5
      auto_dismiss: True
      title: 'Hello world'
      AnchorLayout:
          anchor_x: 'center'
          anchor_y: 'center'
          AnchorLayout:
              anchor_x: 'center'
              anchor_y: 'bottom'
              Button:
                  text: 'Click me to dismiss'
                  on_press: root.dismiss()
          AnchorLayout:
              anchor_x: 'center'
              anchor_y: 'center'
              BoxLayout:
                  orientation: 'vertical'
                  Slider:
                      value: root.color[0] = self.value
                  Slider:
                      value: root.color[1] = self.value
                  Slider:
                      value: root.color[2] = self.value
  </code></pre>
  
  <p>And here's the Python file:</p>
  
  <pre><code>from kivy.app import App
  from kivy.uix.scatter import Scatter
  from kivy.uix.button import Button
  from kivy.uix.popup import Popup
  from kivy.uix.label import Label
  from kivy.uix.floatlayout import FloatLayout
  from kivy.uix.textinput import TextInput
  from kivy.uix.boxlayout import BoxLayout
  from kivy.uix.screenmanager import ScreenManager, Screen
  from kivy.uix.colorpicker import ColorPicker
  from kivy.logger import Logger
  from kivy.graphics import Color, Ellipse, Line
  from kivy.properties import ListProperty
  #from editor import PhotoEditor
  import random
  
  #Each class def is a different screen.
  class WelcomeScreen(Screen):
      def do_stuff():
          pass
  
  class PhoneSelection(Screen):
      pass
  
  class StyleSelection(Screen):
      pass
  
  class ColorSelection(Screen):
      pass
  
  class DesignSelection(Screen):
      pass
  
  class UploadPhoto(Screen):
      pass
  
  class PatternSelection(Screen):
      pass
  
  class PhotoEditor(Screen):
      color = ListProperty([1,1,1,1])
      def open_popup(self):
          popup = ColorPopup()
          popup.open()
  
  class Confirm(Screen):
      pass
  
  class Pay(Screen):
      pass
  
  class ThankYou(Screen):
      pass
  
  class ColorPopup(Popup):
      pass
  
  class Variables():
      phone_type = ""
      phone_color = ""
      phone_style = ""
      phone_design_option = ""
      total_price = 0.0
  
  #This is the main class that has all the app info.
  class MainApp(App):
      #list of names for each screen. Each name is used as an ID when changing the current screen.
      screens = ["welcome","choose_phone","choose_style","choose_color","choose_design","upload_photo","choose_pattern","photo_edit","confirm","pay","thanks"]
      vars = Variables()
      def build(self):
          #The manager that holds all the screens and allows transitioning between them.
          SM = ScreenManager()
  
          #list of names for each screen. Each name is used as an ID when changing the current screen.
          screens = ["welcome","choose_phone","choose_style","choose_color","choose_design","upload_photo","choose_pattern","photo_edit","confirm","pay","thanks"]
  
          #Add all screens to the manager and assign the corresponding ID.
          SM.add_widget(WelcomeScreen(name=screens[0]))
          SM.add_widget(PhoneSelection(name=screens[1]))
          SM.add_widget(StyleSelection(name=screens[2]))
          SM.add_widget(ColorSelection(name=screens[3]))
          SM.add_widget(DesignSelection(name=screens[4]))
          SM.add_widget(UploadPhoto(name=screens[5]))
          SM.add_widget(PatternSelection(name=screens[6]))
          SM.add_widget(PhotoEditor(name=screens[7]))
          SM.add_widget(Confirm(name=screens[8]))
          SM.add_widget(Pay(name=screens[9]))
          SM.add_widget(ThankYou(name=screens[10]))
  
          #Set the current screen to the welcome screen.
          SM.current = screens[0]
          return SM
  
  #Runs the app.
  if __name__ == "__main__":
      t = MainApp();
      t.run()
  </code></pre>