Python – Change kivy button size and position using kv file

Kivy is a platform independent GUI tool in Python. As it can be run on Android, IOS, linux and Windows etc. It is basically used to develop the Android application, but it does not mean that it can not be used on Desktops applications.
In this article we will see that how can we can change the size and the position of button in kivy python in kv file.

size : This is for static sizing of widgets and takes two arguments i.e. (width, height). Default size of the button = (100, 100). 

Syntax: b1 = Button(size=(100, 100))

pos : This is for static placement of widgets and is used to give position to button and by default it is (0, 0) which is the bottom-left corner of the screen. 

Syntax : b1 = Button(pos=(100, 100))

size_hint : This is for dynamic sizing of the button and provide hint of size. It contains two arguments i.e. width and height it can be floating values.By default, all widgets have their size_hint=(1, 1). 

Python3

button = Button(
   text='Hello world',
   size_hint=(.5, .25))

pos_hint : This is for dynamic placement of the button and provide hint of position. We can define upto 8 keys i.e. it takes arguments in form of dictionary. 

pos_hint = {“x”:1, “y”:1, “left”:1, “right”:1, “center_x”:1, 
                 “center_y”:1, “top”:1, “bottom”:1(“top”:0)}

Python3

button = Button(text='Hello world', size_hint=(.6, .6),
               pos_hint={'x':.2, 'y':.2})

Basic Approach:

1) import kivy
2) import kivyApp
3) import all neaded(like button and layouts to use them)
4) Set minimum version(optional)
5) create Layout class
6) create App class
7) Set up .kv file : Create the buttons and set up the position and size 
8) return Layout/widget/Class(according to requirement)
9) Run an instance of the class
 

Kivy Tutorial – Learn Kivy with Examples.

main.py file implementation of the approach –

Python3

## Sample Python application demonstrating the
## How to set button size and position in Kivy using .kv file

###################################################
# import modules
import kivy

# base Class of your App inherits from the App class.
# app:always refers to the instance of your application
from kivy.app import App

# module consist the floatlayout
# to work with FloatLayout first
# you have to import it
from kivy.uix.floatlayout import FloatLayout

# creating the root widget used in .kv file
class FloatLayout(FloatLayout):
    pass

# creating the App class in which name
#.kv file is to be named Float_Layout.kv
class BtnApp(App):
    # defining build()
    def build(self):
        # returning the instance of root class
        return FloatLayout()

# run the app
if __name__ == "__main__":
    BtnApp().run()

btn.kv file implementation of the approach – 

Python3

#.kv file implementation of setting position and size of btn
<FloatLayout>:

    Button:
        text: "pos_hint "
        background_color: 0.1, 0.5, 0.6, 1

        # Giving size hint i.e size of button is
        # 30 % by height and width of layout .
        size_hint: 0.3, 0.3

        # positioned at 0 % right and 100 % up / top
        # from bottom left, i.e x, top = 0, 100 from bottom left:
        pos_hint: {"x":0, "top":1}


    Button:
        text:"pos"
        background_color: 0.4, 0.5, 0.6, 1
        size_hint: 0.3, 0.3
        pos: 100, 100

    Button:
        text:"size_hint"
        background_color: 0, 0, 1, 1

        # Giving size hint i.e size of button is
        # 40 % by height and  50 % width of layout .
        size_hint: 0.5, 0.4
        pos_hint: {"x":.4, "top":1}

Output: