Converting feet to meter and vice versa using on focus out event of Entry widget in Tkinter

Tkinter application to covert feet measurement into meter unit & vice versa with on focus out event

If the user enters data as feet then on mouse out ( lost focus ) our application will convert the same to meter. Similarly if the user enteres data in meter then we will get the output as feet.

Here is the formula used.

1 Feet = 0.3048 Meter 
1 Meter = 3.2808 Feet

Select all text on focus

For easy updating of data in entry boxes we can select all the text once the mouse enters or the entry boxe is in focus.

m1.bind("<FocusIn>",lambda x: m1.select_range(0,tk.END))
f1.bind("<FocusIn>",lambda x: f1.select_range(0,tk.END))

Here m1 is our Entry box to accept data in Meter and f1 is the Entry box to accept data in feet.

Triggering the conversion of data

Once the mouse moves out or if the Entry widget lost the focus then the conversion should happen. Here are the events that triggers the functions.

m1.bind("<FocusOut>",my_upd2)
f1.bind("<FocusOut>",my_upd1)

Inside the functions we used get() and set() methods of DoubleVar() to collect and update the data. After the conversion we used round() to restrict the output to 2 decimal places.

def my_upd1(*args): # data entered as feet 
    m1_var.set(round(f1_var.get()*0.3048,2))

Full code is here

import tkinter as tk
from tkinter import END
my_w = tk.Tk()
my_w.geometry("800x500")  # Size of the window 
my_w.title("www.plus2net.com")  # Adding a title
font1=('Times',34,'normal') # font size 

l1 = tk.Label(my_w,  text='Meter', width=10,font=font1 )  #  Label 
l1.grid(row=0,column=0,padx=10,pady=10) 

m1_var=tk.DoubleVar() # Double variable 
m1 = tk.Entry(my_w,width=10,bg='yellow',font=font1,textvariable=m1_var) 
m1.grid(row=0,column=1,padx=10) 

l2 = tk.Label(my_w,  text='Feet', width=10,font=font1 )  #  Label 
l2.grid(row=1,column=0,padx=10,pady=10) 

f1_var=tk.DoubleVar()
f1 = tk.Entry(my_w,width=10,bg='yellow',font=font1,textvariable=f1_var) 
f1.grid(row=1,column=1,padx=10) 
# Layout is over #

def my_upd1(*args): # data entered as feet 
    m1_var.set(round(f1_var.get()*0.3048,2))

def my_upd2(*args): # data entered as meter
    f1_var.set(round(m1_var.get()*3.2808,2))    

m1.bind("<FocusOut>",my_upd2) # lost focus 
f1.bind("<FocusOut>",my_upd1)

# Selection of all data on focus 
m1.bind("<FocusIn>",lambda x: m1.select_range(0,tk.END))
f1.bind("<FocusIn>",lambda x: f1.select_range(0,tk.END))
my_w.mainloop()  # Keep the window open

Using third measurement unit Kadi

Kadi is popular in land measurment where chains are used and each chain is considered as one Kadi.

1 Feet = 0.3048 Meter 
1 Meter = 3.2808 Feet
1 Kadi = 0.66 Feet

To our above code we will add one more input and integrate the same to get output in all units. User can add data in any one of the input Entry widget and on focus out, other two will show the equivalent values in respective units.

import tkinter as tk
from tkinter import END
my_w = tk.Tk()
my_w.geometry("800x500")  # Size of the window 
my_w.title("www.plus2net.com")  # Adding a title
font1=('Times',34,'normal')

l1 = tk.Label(my_w,  text='Meter', width=10,font=font1 )  # Label 
l1.grid(row=0,column=0,padx=10,pady=10) 
m1_var=tk.DoubleVar()
m1 = tk.Entry(my_w,width=10,bg='yellow',font=font1,textvariable=m1_var) 
m1.grid(row=0,column=1,padx=10) 

l2 = tk.Label(my_w,  text='Feet', width=10,font=font1 )  # Label 
l2.grid(row=1,column=0,padx=10,pady=10) 

f1_var=tk.DoubleVar()
f1 = tk.Entry(my_w,width=10,bg='yellow',font=font1,textvariable=f1_var) 
f1.grid(row=1,column=1,padx=10) 

l3 = tk.Label(my_w,  text='Kadi', width=10,font=font1 )  #  Label 
l3.grid(row=2,column=0,padx=10,pady=10) 

k1_var=tk.DoubleVar()
k1 = tk.Entry(my_w,width=10,bg='yellow',font=font1,textvariable=k1_var) # text box
k1.grid(row=2,column=1,padx=10) 

def my_upd1(*args): # feet is entered 
    in_meeter=round(f1_var.get()*0.3048,2)
    m1_var.set(in_meeter)
    k1_var.set(round(f1_var.get()*0.66,2))
def my_upd2(*args): # meeter is entered 
    in_feet=m1_var.get()*3.2808
    f1_var.set(round(in_feet,2))    
    k1_var.set(round(in_feet/0.66,2))
def my_upd3(*args): # kadi is entered 
    in_feet=k1_var.get()*0.66
    m1_var.set(round(in_feet*0.3048,2))    
    f1_var.set(round(in_feet,2))

f1.bind("<FocusOut>",my_upd1)
m1.bind("<FocusOut>",my_upd2)
k1.bind("<FocusOut>",my_upd3)

m1.bind("<FocusIn>",lambda x: m1.select_range(0,tk.END))
f1.bind("<FocusIn>",lambda x: f1.select_range(0,tk.END))
k1.bind("<FocusIn>",lambda x: k1.select_range(0,tk.END))
my_w.mainloop()  # Keep the window open

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Converting feet and meter values

Select all text on focus

Triggering the conversion of data

Using third measurement unit Kadi

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