title: How to input/use float through Entry box tkinter Python?
body: <p>I am trying to learn about tkinter so i create small GUI python to input 2 numbers and use their <code>tk.Entry()</code> box to input number and find the sum of both. But I fail to update the float number and generate their sum. Can anyone help add some components so to make it work? When i generate the result , it only show 0 which is the initial value of variable.</p>
  
  <pre><code>import tkinter as tk
  from tkinter import *
  
  root = tk.Tk()
  root.title("Shear and Moment Diagram Calculator")
  operator=""
  
  canvas = tk.Canvas(root, height=400,width=500,bg="White")
  canvas.pack()
  frame=tk.Frame(root, bg="Light Blue")
  frame.place(relwidth=0.9,relheight=0.9, relx=0.05, rely=0.05)
  
  num1 = float()
  num2 = float()
  
  tk.Label(frame, font =("Helvetica", 20),
          text="Number 1:" ).grid(row=0)
  
  tk.Label(frame, font =("Helvetica", 20),
          text="Number 2:" ).grid(row=1,column=0)
  
  num1= tk.Entry(frame, textvariable = num1 ).grid(row=0, column = 1)
  num2= tk.Entry(frame, textvariable = num2 ).grid(row=1, column = 1)
  
  def generate():
      num3= num1 + num2
      print(num3)
  
  
  generate=tk.Button(frame, text="result", height="2", width="10",
                     fg="Black", bg="yellow", command = generate )
  generate.grid(row=2, column=2)
  
  mainloop()
  </code></pre>