how do i set the input value to 150 as default? n if i enter non-integer value how can i validate it?? thanks

from Tkinter import *
root = Tk()
lbl = Label(root, text = "Enter Number of vehicles", bg = 'blue', fg= 'white')
lbl.pack()
textbox = Entry(root, width="20", textvariable=IntVar())
textbox.pack()

Button(root, text='Click ').pack(ipadx =1,padx =1, pady=1)

Here is one way to do this ...

# use Tkinter's dialogs to ask for input
# dialogs are askfloat, askinteger, and askstring

import Tkinter as tk
from tkSimpleDialog import askinteger

def get_age():
    # keeps asking until you enter an integer value
    age = askinteger("Age", "Enter your age")
    int_var.set(age)

root = tk.Tk()
int_var = tk.IntVar()

tk.Button(root, text="Get age", command=get_age).pack(pady=5)
tk.Label(root, textvariable=str(int_var)).pack()

root.mainloop()