Using local variables in a KV file

[Colin Brett]

Hi,

The app I'm working on needs to pass a variable set by a checkbox in the KV file back to the main Python program. The relevant section of the KV file is:

<SelectGenre>:

    GridLayout:

        cols: 2

        Label:

            text:'Fantasy'

        CheckBox:

            group: 'genre_group'

            on_active: root.fantasy_genre(*args)

            #:set genre 'fantasy'

        Label:

            text:'Sci-Fi'

        CheckBox:

            group: 'genre_group'

            on_active: root.scifi_genre(*args)

            #:set genre 'scifi'

        Label:

            text:'Cyberpunk'

        CheckBox:

            group: 'genre_group'

            on_active: root.cyberpunk_genre(*args)

            #:set genre 'cyberpunk'

        Label:

            text:'Wild West'

        CheckBox:

            group: 'genre_group'

            on_active: root.wildwest_genre(*args)

            #:set genre 'wildwest'

        Label:

            text:'Horror'

        CheckBox:

            group: 'genre_group'

            on_active: root.horror_genre(*args)

            #:set genre 'horror'

        Button:

            text:'Back'

            on_press: root.manager.current = 'welcome'

        Button:

            text:'Next'

#           on_press: root.manager.current = 'race'

            on_press: root.choose_race_screen(genre)

I want to pass the variable for the chosen genre into the following Python function:

 class SelectGenre(Screen):

#   pass

#self.manager.genre = ''

    def choose_race_screen(self,args):

        print (self)

        print (args)

        print (*args)

        race_display = args

        print ("Race display =", race_display)

        if race_display == 'fantasy':

            sm.current = 'race_fantasy'

        if race_display == 'scifi':

            sm.current = 'race_scifi'

        if race_display == 'cyberpunk':

            sm.current = 'race_cyberpunk'

        if race_display == 'wildwest':

            sm.current = 'race_wildwest'

        if race_display == 'horror':

            sm.current = 'race_horror'

The idea being, if a scifi genre is chosen, the races appropriate to that genre will be displayed next. What's happening is that no matter which genre I select, it always ends up as "horror".

Now, I think variables set with the #:set construct in the KV file are treated as global variables and that (presumably) the last option in the <SelectGenre> screen overrides all the others. Is this correct?

So the question is: how do I set a local variable in the KV file which can be successfully passed to the choose_race_screen function?

Please let me know if any further information is needed.

Regards,

Colin Brett

[ZenCODE]

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen, SlideTransition
from kivy.properties import StringProperty


class SelectGenre(Screen):
    genre = StringProperty()

    def choose_race_screen(self):
        print("Race display =", "_".join(['race', self.genre]))
        # sm.current = "_".join(['race', race])


class MainApp(App):
    def build(self):
        Builder.load_file('<your_kv_file>.kv')
        return SelectGenre()

if __name__ == '__main__':

    MainApp().run()

========================
'<your_kv_file>.kv'
========================

<SelectGenre>:
    GridLayout:
        cols: 2
        Label:
            text:'Fantasy'
        CheckBox:
            group: 'genre_group'

            on_active: root.genre = 'fantasy'

            #:set genre 'fantasy'
        Label:
            text:'Sci-Fi'
        CheckBox:
            group: 'genre_group'

            on_active: root.genre = 'scifi'

            #:set genre 'scifi'
        Label:
            text:'Cyberpunk'
        CheckBox:
            group: 'genre_group'

            on_active: root.genre = 'cyberpunk'

            #:set genre 'cyberpunk'
        Label:
            text:'Wild West'
        CheckBox:
            group: 'genre_group'

            on_active: root.genre = 'wildwest'

            #:set genre 'wildwest'
        Label:
            text:'Horror'
        CheckBox:
            group: 'genre_group'

            on_active: root.genre = 'horror'

            #:set genre 'horror'
        Button:
            text:'Back'
            on_press: root.manager.current = 'welcome'
        Button:
            text:'Next'
#           on_press: root.manager.current = 'race'

            on_press: root.choose_race_screen()

[Colin Brett]

Hi ZenCODE,

Your suggestions worked like a charm. Thank you very much.

Colin

PS: How can I +1 your post?

On Wednesday, August 3, 2016 at 9:03:11 PM UTC+1, Colin Brett wrote:

[ZenCODE]

Glad it worked :-)

There is a star at the top left of the post, next to the first line.

ps. I should probably point out that 'on_active' will fire also for a deactivate, then the activate, so the above is not 100% optimal. You could have:

on_active: if args[1]: root.genre = "blah"

so that it only fires when the active state is True (args are the parameters passed to the 'on_active' event). But I really doubt that is an issue in this case...