Kivy Button changing values unwantedly (size_hint) - python-3.x

Question

So, i've been studying the kivy library for a couple of days and I did a simple app with some screens simulating a SignIn/Register enviroment. What i noticed is, in my .kv file, when I set "global parameters" to my widgets, the Button parameters are simply not changing. Take a look:
#: import FadeTransition kivy.uix.screenmanager.FadeTransition
Gerencia:
transition: FadeTransition()
TelaDeLogin:
TelaDeCadastro:
TelaEsqueci:
TelaEmDesenvolvimento:
<Button>:
size_hint: 1, 0.1
font_size: 40
color: 1, 1, 1, 1
<Label>:
size_hint: 0.5, 0.1
color: 1, 1, 0, 1
font_size: 40
<TextInput>:
multiline: False
size_hint: 0.5, 0.1
<TelaDeLogin>:
name: "Login"
FloatLayout:
Button:
on_release: app.root.current = "Desenvolvimento"
pos_hint: {'x':0, 'y':0.2}
text: 'Logar'
Button:
on_release: app.root.current = "Esqueci"
pos_hint: {'x':0, 'y':0.1}
text: 'Esqueci a senha'
Button:
on_release: app.root.current = "Cadastro"
pos_hint: {'x':0, 'y':0}
text: 'Cadastre-se'
Label:
text: "Usuário"
pos_hint: {'x':0.25, 'y':0.8}
TextInput:
pos_hint: {'x':0.25, 'y':0.7}
Label:
text: "Senha"
pos_hint: {'x':0.25, 'y':0.6}
TextInput:
password: True
pos_hint: {'x':0.25, 'y':0.5}
I'm ommiting some other screens but they are irrelevant, what happened was, I did some tests and changing the size_hint inside of "<"Button">" doesn't affect the size of my Buttons at all, they are apparently just getting some default size. Another weird thing that happened was, just to test, I did some changes to font_size both inside "<"Button">" and inside "<"Label">", and the value I put into Label also affected my Buttons on the screen, same happened with color. So it seems like my Buttons are getting their values from "<"Label">" and not from "<"Button>". Does anyone have any Idea what's going on?

Answer 1

Explanation
You have overwritten the base class Label, and Button is a Label as specified in the following Kivy documentation. In your Kivy App, Button has inherited the size_hint, font_size and color from your customized Label.
Button
The Button is a Label with associated actions that are triggered when
the button is pressed (or released after a click/touch). To configure
the button, the same properties (padding, font_size, etc) and sizing
system are used as for the Label class
Solution
Create dynamic classes for Label and Button.
Create a dynamic class with inheritance from Button. Replace instantied children, Button: with MyButton:
Create a dynamic class with inheritance from Label. Replace instantied children, Label: with MyLabel:
Snippets
<MyButton#Button>:
size_hint: 1, 0.1
font_size: 40
color: 1, 1, 1, 1
<MyLabel#Label>:
size_hint: 0.5, 0.1
color: 1, 1, 0, 1
font_size: 40
...
<TelaDeLogin>:
name: "Login"
FloatLayout:
MyButton:
on_release: app.root.current = "Desenvolvimento"
pos_hint: {'x':0, 'y':0.2}
text: 'Logar'
MyButton:
on_release: app.root.current = "Esqueci"
pos_hint: {'x':0, 'y':0.1}
text: 'Esqueci a senha'
MyButton:
on_release: app.root.current = "Cadastro"
pos_hint: {'x':0, 'y':0}
text: 'Cadastre-se'
MyLabel:
text: "Usuário"
pos_hint: {'x':0.25, 'y':0.8}
TextInput:
pos_hint: {'x':0.25, 'y':0.7}
MyLabel:
text: "Senha"
pos_hint: {'x':0.25, 'y':0.6}
TextInput:
password: True
pos_hint: {'x':0.25, 'y':0.5}
Output