Label not aligned correctly - python-3.x

Question

I am using pydev on eclipse luna. My kv file is as follows:
<LoginForm>:
userid: userid
password: password
size_hint_x: 0.5
size_hint_y: None
height: 200
orientation: 'vertical'
pos_hint: {'center_x': 0.5,'center_y':0.5}
minimum_height: 100
minimum_width: 100
#User ID
Label:
text: 'User ID'
font_size: 20
size_hint_x: None
TextInput:
id: userid
font_size: 20
#User PW
Label:
text: 'Password'
font_size: 20
TextInput:
id: password
password: True
font_size: 20
Button:
text: 'Login'
My python code is:
from kivy.app import App;
from forms.login import LoginForm;
from kivy.core.window import Window
from kivy.uix.boxlayout import BoxLayout
class LoginForm(BoxLayout):
def __init__(self, **kwargs):
super(LoginForm, self).__init__(**kwargs)
class StartApp(App):
def build(self):
Window.size = (480, 800)
return LoginForm()
#return StartApp();
if __name__ == '__main__':
StartApp().run()
Output:
The code is working correctly, however, my issue is that there is still some gap at left which is not present for other controls. I want User ID to be completely left aligned (in the above pic it is left aligned, but some space is still left).
Could you please advice/correct me on where I went wrong?

Answer 1

The Label isn't left-aligned because you haven't actually set that, by disabling the size_hint_x it just takes the default width of 100 pixels and the text appears in its centre.
You have two options for declaring the label.
Label:
text: 'User ID'
font_size: 20
size_hint_x: None
width: self.texture_size[0]
This will set the width of the Label to the exact size of the texture containing the image of the text. However, I think it's probably preferable to do the following:
Label:
text: 'User ID'
font_size: 20
text_size: self.size
halign: 'left'
valign: 'middle'
This way, rather than messing with the widget size/position you set the text_size (this controls the bounding box of the text texture) and the built in text alignment options take care of the rest.
In this case, the results of these should be similar if not identical.