I am trying to make a simple random number generator GUI, and for some reason I get an error trying to take the text out txt1 and txt2. Why isn't this working? The error says AttributeError: 'NoneType' object has no attribute 'get'

Code:
from Tkinter import *
import random
class myform:
    def __init__(self,form):
        form.wm_title('Random')
        lbl1=Label(form,text='Low:').grid(row=0)
...