How do I use a variable from one class function in another class function

Eric B

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Mar 9, 2020, 5:20:15 PM3/9/20

to Kivy users support

The RBox class gives me a reason, and the get_reason function gets called whenever a radio button is pressed so I know there's a reason that can get printed. When I run the pressed function though from a button, the reason doesn't get printed, please help.

class RBox(GridLayout):
    def get_reason(self):
        reason = self.ids.reason.text
        print(reason)


class FormScreen(BoxLayout):
    def pressed(self):

RBox().get_reason()

Elliot Garbus

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Mar 9, 2020, 5:43:08 PM3/9/20

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It is easier to answer these questions if you attach a complete runnable example.

The problem below is the RBox().

class FormScreen(BoxLayout):
def pressed(self):

RBox().get_reason

When you say RBox() you are creating a new RBox object, you want to access the existing RBox object. You can do this by giving the RBox an id in KV.

RBox:

id: my_rbox

Then change FormScreen to something like:

class FormScreen(BoxLayout):
def pressed(self):

app = App.get_running_app()

app.root.ids.my_rbox.get_reason()

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Message has been deleted

Eric B

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Mar 9, 2020, 6:03:56 PM3/9/20

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My message got deleted?

Heres the runnable code:


class RBox(GridLayout):
    def get_reason(self):
        reason = self.ids.reason.text

        return reason

class FormScreen(BoxLayout):
    def pressed(self):

 
class MainApp(App):
    def build(self):
        return FormScreen()


if __name__ == "__main__":
    MainApp().run()

<RBox>:
    cols: 2
    text: ''
    group: ''
    RCheckBox:
        id: cb
        group: root.group
        on_active: root.get_reason()
    RLabel:
        on_press: cb._do_press()
        text: root.text
        width: root.width*0.5
        id: reason

Elliot Garbus

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Mar 9, 2020, 7:17:36 PM3/9/20

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This code is not complete. There are no imports. There are other obvious errors in the code.

From: Eric B
Sent: Monday, March 9, 2020 3:04 PM
To: Kivy users support

Subject: [kivy-users] Re: How do I use a variable from one class function inanother class function

My message got deleted?

Heres the runnable code:


class RBox(GridLayout):
    def get_reason(self):
        reason = self.ids.reason.text
        return

reason
This cclass FormScreen(BoxLayout):
    def pressed(self):

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Eric B

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Mar 9, 2020, 7:24:33 PM3/9/20

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from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout




class RBox(GridLayout):
    def get_reason(self):
        reason = self.ids.reason.text

        return reason



class FormScreen(BoxLayout):
    def pressed(self):



class MainApp(App):
    def build(self):
        return FormScreen()


if __name__ == "__main__":
    MainApp().run()

<RBox>:
    cols: 2
    text: ''
    group: ''

    CheckBox:
        id: cb
        group: root.group
        on_active: root.get_reason()

    Label:
        on_press: cb._do_press()
        text: root.text
        width: root.width*0.5
        id: reason

<FormScreen>:

    Button:

        text: "Submit"

        on_press: root.pressed()

Elliot Garbus

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Mar 9, 2020, 9:51:59 PM3/9/20

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It is hard for me to tell what you are trying to do. Here is an example I put together for another developer. I’ve highlighted a few pieces of code. Note <AnotherClass@BoxLayout> defines the class.

AnotherClass: instances the class.

Each kivy ‘rule’ has it’s own ids dictionary. see print(f'And another layer down: {app.root.ids.instance_ac.ids}')

The id in kv code, at the time kv code is parsed, gets turned into a dictionary of ids, the dictionary associates the id with the widget.

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout

from kivy.lang import Builder

kv = """
<AnotherClass@BoxLayout>
    Label:
        id: label
        text: 'Here i am'
    Button:
        id: button
        text: 'I do nothing'


Tab1BoxLayout:
    id: box10
    orientation: 'vertical'

    Label:
        id: label10
        text: 'Second tab content area'
    Button:
        id: button10
        text: 'print ids'
        on_release:
            root.print_from_python()
            print(f'Print from KV: {app.root.ids}')
            print(f'And another layer down: {app.root.ids.instance_ac.ids}')
        

    BoxLayout:
        id: box20
        orientation: 'vertical'

        Label:
            id: label20
            text: 'Label 2'
        AnotherClass:
            id: instance_ac

"""


class Tab1BoxLayout(BoxLayout):
    def print_from_python(self):
        app = App.get_running_app()
        print(f'ids from Python {app.root.ids}')
        print(f'This is the same, because self is the root widget: {self.ids}')
        print(f'For this case, the app.root.ids dictionary and the self.ids dictionary is the same: {app.root.ids is self.ids}')


class AppRootProblemApp(App):
    def build(self):
        return Builder.load_string(kv)


if __name__ == '__main__':
    AppRootProblemApp().run()

From: Eric B
Sent: Monday, March 9, 2020 4:24 PM
To: Kivy users support
Subject: [kivy-users] Re: How do I use a variable from one class function inanother class function

from kivy.app import App

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Elliot Garbus

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Mar 10, 2020, 3:53:17 PM3/10/20

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I made a few modifications.

I instanced the root widget FormScreen in kv. I put 2 instances of RBox under FormScreen.

RLabel, RCheckBox, were not defined so I replaced them.

Added print messages to illustrate what is going on.

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout

from kivy.lang import Builder

kv =

"""


<RBox>:
    cols: 2
    text: ''
    group: ''

    # RCheckBox:  # Not Defined


    CheckBox:
        id: cb
        group: root.group
        on_active: root.get_reason()

    # RLabel:  # Not Defined
    Button:                   # Label does not have an on_press, changed to button
        id: reason
        on_press:            
            cb._do_press() 
            app.root.pressed()  # added call to pressed()
        text: root.text
        

FormScreen: # Root widget
    RBox:
        text: 'Test RBox 1'
        group: 'test'
    RBox:
        id:my_rbox
        text: 'Text RBox 2'
        group: 'test'
"""

class RBox(GridLayout):
    def get_reason(self):
        reason = self

.ids.reason.text
        print(f'get reason called, reason = {reason}')
        return reason


class FormScreen(BoxLayout):
    def pressed(self):
        print('pressed called')
        app = App.get_running_app()
        app.root.ids.my_rbox.get_reason()
        print(f'app.root.ids = {app.root.ids}')
        print(f'app.root.ids.my_rbox.ids = {app.root.ids.my_rbox.ids}')


class Main_1App(App):
    def build(self):
        return Builder.load_string(kv)

if __name__ == "__main__":
    Main_1App().run()

From: Eric B
Sent: Tuesday, March 10, 2020 12:09 PM
To: Kivy users support
Subject: [kivy-users] Re: How do I use a variable from one class function inanother class function

When I tried that I got this error: KeyError: 'my_rbox' and AttributeError: 'super' object has no attribute '__getattr__'

Here is the runnable code:

#Python Code

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout

class RBox(GridLayout):
    def get_reason(self):
        reason = self.ids.reason.text
        return reason

class FormScreen(BoxLayout):
    def pressed(self):
        app = App.get_running_app()
        app.root.ids.my_rbox.get_reason()

class MainApp(App):
    def build(self):
        return FormScreen()

if __name__ == "__main__":
    MainApp().run()

#.kv Code

<RBox>:
    cols: 2
    text: ''
    group: ''

    id: my_rbox
    RCheckBox:


        id: cb
        group: root.group
        on_active: root.get_reason()

    RLabel:


        on_press: cb._do_press()
        text: root.text
        width: root.width*0.5
        id: reason

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