python - Unloading Kivy builder rules more than once, in order to re-import GUI elements from files - Stack Overflow

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I would like to import optional GUI elements defined in separate Mod1.py/Mod2.py/etc files and add/remove these dynamically from the main GUI. The separate files that define these optional GUI elements, contain kv strings. In my use case, these GUI elements can be unloaded/reloaded multiple times. I discovered that if I have identically named classes in the Modx.py files, this creates cross-talk between the modules because Builder.load_string works cumulatively. The background to this discovery is here - Importing multiple modules containing identically named class in python

Kivy Builder documentation suggests that a given kv string can be selectively unloaded later if a pseudo filename is supplied e.g. Builder.load_string("""<kv string>""", filename="myrule.kv") and later to unload - Builder.unload_file("myrule.kv") However when I try this, it appears to work only the first time a module is unloaded and another one is loaded. After that the optional GUI elements no longer appear when reloaded. The following example demonstrates this.

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.button import Button
from kivy.lang import Builder
import importlib

Builder.load_string('''
<MainWidget>:
    orientation: 'vertical'
    BoxLayout:
        Button:
            text: "Load Mod 1"
            on_press: 
                root.load_module(self.text)
        Button:
            text: "Load Mod 2"
            on_press: 
                root.load_module(self.text)
        Button:    
            text: "Unload all"
            on_press: 
                dock.clear_widgets()
    FloatLayout: 
        id: dock
''')
    
class MainWidget(BoxLayout):
    
    def load_module(self, hint):

        self.ids.dock.clear_widgets()
        Builder.unload_file("foo.kv")

        if "1" in hint:
            self.module = importlib.import_module("Mod1").Module()
        if "2" in hint:
            self.module = importlib.import_module("Mod2").Module()
        
        self.ids.dock.add_widget(self.module)

class MyApp(App):
    def build(self):
        return MainWidget()
      
if __name__ == '__main__':
    MyApp().run()

Mod1.py

from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder

Builder.load_string('''
<Module>:  
    size_hint: None, None
    size: self.parent.size if self.parent else self.size
    pos: self.parent.pos if self.parent else self.pos
    Button:
        size_hint: None, None
        width: self.parent.width / 3
        height: self.parent.height
        pos: self.parent.pos
        text: "Mod 1"
        on_press: print(root); print([x for x in dir(root) if 'method' in str(x)])
''', filename="foo.kv")

class Module(FloatLayout):

    def __init__(self, **kwargs):
        super(FloatLayout, self).__init__(**kwargs)
        
    def dummymethod1(self):
        pass

Mod2.py

from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder

Builder.load_string('''
<Module>:
    size_hint: None, None
    size: self.parent.size if self.parent else self.size
    pos: self.parent.pos if self.parent else self.pos
    Button:
        size_hint: None, None
        width: self.parent.width / 3
        height: self.parent.height
        pos: (self.parent.x + self.parent.width / 2) , self.parent.y
        text: "Mod 2"
        on_press: print(root); print([x for x in dir(root) if 'method' in str(x)])
''', filename="foo.kv")

class Module(FloatLayout):

    def __init__(self, **kwargs):
        super(FloatLayout, self).__init__(**kwargs)
        
    def dummymethod2(self):
        pass

I would like to know if there is a way to make this work properly. Perhaps I am missing something about the way Kivy builder functions?

I would like to import optional GUI elements defined in separate Mod1.py/Mod2.py/etc files and add/remove these dynamically from the main GUI. The separate files that define these optional GUI elements, contain kv strings. In my use case, these GUI elements can be unloaded/reloaded multiple times. I discovered that if I have identically named classes in the Modx.py files, this creates cross-talk between the modules because Builder.load_string works cumulatively. The background to this discovery is here - Importing multiple modules containing identically named class in python

Kivy Builder documentation suggests that a given kv string can be selectively unloaded later if a pseudo filename is supplied e.g. Builder.load_string("""<kv string>""", filename="myrule.kv") and later to unload - Builder.unload_file("myrule.kv") However when I try this, it appears to work only the first time a module is unloaded and another one is loaded. After that the optional GUI elements no longer appear when reloaded. The following example demonstrates this.

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.button import Button
from kivy.lang import Builder
import importlib

Builder.load_string('''
<MainWidget>:
    orientation: 'vertical'
    BoxLayout:
        Button:
            text: "Load Mod 1"
            on_press: 
                root.load_module(self.text)
        Button:
            text: "Load Mod 2"
            on_press: 
                root.load_module(self.text)
        Button:    
            text: "Unload all"
            on_press: 
                dock.clear_widgets()
    FloatLayout: 
        id: dock
''')
    
class MainWidget(BoxLayout):
    
    def load_module(self, hint):

        self.ids.dock.clear_widgets()
        Builder.unload_file("foo.kv")

        if "1" in hint:
            self.module = importlib.import_module("Mod1").Module()
        if "2" in hint:
            self.module = importlib.import_module("Mod2").Module()
        
        self.ids.dock.add_widget(self.module)

class MyApp(App):
    def build(self):
        return MainWidget()
      
if __name__ == '__main__':
    MyApp().run()

Mod1.py

from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder

Builder.load_string('''
<Module>:  
    size_hint: None, None
    size: self.parent.size if self.parent else self.size
    pos: self.parent.pos if self.parent else self.pos
    Button:
        size_hint: None, None
        width: self.parent.width / 3
        height: self.parent.height
        pos: self.parent.pos
        text: "Mod 1"
        on_press: print(root); print([x for x in dir(root) if 'method' in str(x)])
''', filename="foo.kv")

class Module(FloatLayout):

    def __init__(self, **kwargs):
        super(FloatLayout, self).__init__(**kwargs)
        
    def dummymethod1(self):
        pass

Mod2.py

from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder

Builder.load_string('''
<Module>:
    size_hint: None, None
    size: self.parent.size if self.parent else self.size
    pos: self.parent.pos if self.parent else self.pos
    Button:
        size_hint: None, None
        width: self.parent.width / 3
        height: self.parent.height
        pos: (self.parent.x + self.parent.width / 2) , self.parent.y
        text: "Mod 2"
        on_press: print(root); print([x for x in dir(root) if 'method' in str(x)])
''', filename="foo.kv")

class Module(FloatLayout):

    def __init__(self, **kwargs):
        super(FloatLayout, self).__init__(**kwargs)
        
    def dummymethod2(self):
        pass

I would like to know if there is a way to make this work properly. Perhaps I am missing something about the way Kivy builder functions?

• python
• kivy
• kivy-language

Share Improve this question Follow asked yesterday Eugene BEugene B 6177 bronze badges 1

• I don't understand why you want to uload it. If you want to use different kv code then maybe keep it in separated file and load it as normal text file - with open(), read(), close(). OR maybe you need remove_widget to remove previous content and later use add_widget to add new content. – furas Commented yesterday

Add a comment  | 

1 Answer 1

Sorted by: Reset to default 2

I think the importlib will not import a module if it has already been loaded. In that case, you can use importlib.reload(). Try modifying your MainWidget class to do that. Something like:

class MainWidget(BoxLayout):
    def __init__(self):
        self.current_module1 = None
        self.current_module2 = None
        super(MainWidget, self).__init__()

    def load_module(self, hint):

        self.ids.dock.clear_widgets()
        Builder.unload_file("foo.kv")

        if "1" in hint:
            if self.current_module1:
                self.current_module1 = importlib.reload(self.current_module1)
            else:
                self.current_module1 = importlib.import_module("Mod1")
            self.module = self.current_module1.Module()
        if "2" in hint:
            if self.current_module2:
                self.current_module2 = importlib.reload(self.current_module2)
            else:
                self.current_module2 = importlib.import_module("Mod2")
            self.module = self.current_module2.Module()

        self.ids.dock.add_widget(self.module)

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