How to read a Kivy.properties.NumericProperty value in my code at a specific point - python-3.x

Question

So basically I have a kivy project in which,I have a layout that I use in many classes,as such..I have made in custom and put it in a separate file so I can just reference it from different parts of my code.
Snippet:
from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder
Builder.load_string('''
<CustLayout>:
#code here
''')
class CustLayout(BoxLayout):
t_length = NumericProperty(0)
my_len = 0
print(my_len)
def __init__(self, **kwargs):
super(Silvertable,self).__init__(**kwargs)
self.bind(t_length=self.on_t_length)
#This statement is executed after all other prints
print(self.t_length)
def on_t_length(self,instance,length):
#I'd like to get kv file value before the next line
self.my_len = length
print(my_len)
My kiv file:
#:import Silvertable silvertables.Silvertable
#chunk of code
BoxLayout:
Silvertable:
t_length: 5
Here,I DO get the value but unfortunately too late.That is,I get the value after the program has finished.my_len Doesn't change it's still 0

Answer 1

Bind Kivy Properties
The value of my_len is 0 (zero) because the print() functions were executed first before the run() method.
The value of my_len did change from 0 to 5 as per binding on property of t_length.
Please refer to the example and trace for details.
Example
main.py
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import NumericProperty
from kivy.lang import Builder
Builder.load_string('''
<CustLayout>:
t_length: 5
''')
class CustLayout(BoxLayout):
t_length = NumericProperty(0)
my_len = 0
print("\tCustLayout.class level-start: my_len=", my_len)
def __init__(self, **kwargs):
super(CustLayout,self).__init__(**kwargs)
print("\nCustLayout.__init__:")
self.bind(t_length=self.on_t_length)
#This statement is executed after all other prints
print("\tself.t_length=", self.t_length)
print("\tself.my_len=", self.my_len)
def on_t_length(self, instance, length):
print("\nCustLayout.on_t_length:")
#I'd like to get kv file value before the next line
self.my_len = length
print("\tself.my_len=", self.my_len)
print("\tCustLayout.class level-end: my_len=", my_len)
class TestBindProperty(App):
def build(self):
print("\nTestBindProperty.build:")
return CustLayout()
def on_stop(self):
print("\tTestBindProperty.on_stop: my_len=", self.root.my_len)
if __name__ == "__main__":
TestBindProperty().run()
Output