Learning Python- Intermediate course: Day 23, IntVar() and Radio-buttons.

x = StringVar() # Holds a string; default value ""x = IntVar() # Holds an integer; default value 0x = DoubleVar() # Holds a floating point integer ; default value 0.0x = BooleanVar() # Holds a Boolean, returns 0 for False and 1 for True

>>> a=IntVar() # You cannot declare a IntVar() without importing TkinterTraceback (most recent call last):  File "<stdin>", line 1, in <module>NameError: name 'IntVar' is not defined>>> from tkinter import *>>> a=Intvar() # mind the Spelling!Traceback (most recent call last):  File "<stdin>", line 1, in <module>NameError: name 'Intvar' is not defined>>> a=IntVar() # You cannot declare a IntVar() before creating a Tk() instance.Traceback (most recent call last):  File "<stdin>", line 1, in <module>  File "C:\Users\aatma\AppData\Local\Programs\Python\Python39\libkinter\__init__.py", line 539, in __init__    Variable.__init__(self, master, value, name)  File "C:\Users\aatma\AppData\Local\Programs\Python\Python39\libkinter\__init__.py", line 346, in __init__    master = _get_default_root('create variable')  File "C:\Users\aatma\AppData\Local\Programs\Python\Python39\libkinter\__init__.py", line 297, in _get_default_root    raise RuntimeError(f"Too early to {what}: no default root window")RuntimeError: Too early to create variable: no default root window>>> master=Tk() # A blank Tkinter window opens >>> a=IntVar() #IntVar() is a class and we are creating an instance of the class.>>> a.set(1) #set the value of a to 1>>> a.get() # get (return) the value of a.1>>> a+2Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: unsupported operand type(s) for +: 'IntVar' and 'int'>>> a.get()+23>>> b=BooleanVar()>>> b.set('True') # set b to 'True'>>> b.get()True>>> c=DoubleVar()>>> c.get()0.0>>> c.set(3)>>> c.get() #automatic float conversion3.0>>> a.get()+c.get() # type converts to floating point automatically when float and integer added.4.0>>> d=StringVar()>>> d.set("hello")>>> str(c.get())+d.get() # the returned values can be used in operations.'3.0hello'>>> a.set(b.get()) # true=1>>> a.get()1>>> a.set(c.get()) # type conversion automatic>>> a.get()3>>> a.set(2.9) # floating points truncated.>>> a.get()2>>> a=d>>> a.get()'hello'

>>> a=IntVar()>>> a=1>>> a.set(1)Traceback (most recent call last):  File "<stdin>", line 1, in <module>AttributeError: 'int' object has no attribute 'set'

from tkinter import *master= Tk()master.title("RadioButton Demo...")master.geometry("300x200")v = IntVar()v.set(-1) #initializing the choice, i.e. no default choicelanguages = ["Python","Java","Swift","JavaScript"]# making an array to choose the programming languages fromStringlbl="My Favourite programming language is.... "# text to display in the labeldef showchoice(): # function to display the result     ResultLabel.config(text= Stringlbl +languages[v.get()])ResultLabel=Label(master,text=Stringlbl)# Make the label                  ResultLabel.pack()#Set the radiobuttonsRadiobutton1=Radiobutton(master,text=languages[0],variable=v,command=showchoice, value=0)Radiobutton2=Radiobutton(master,text=languages[1],variable=v,command=showchoice, value=1)Radiobutton3=Radiobutton(master,text=languages[2],variable=v,command=showchoice, value=2)Radiobutton4=Radiobutton(master,text=languages[3],variable=v,command=showchoice, value=3)Radiobutton1.pack()Radiobutton2.pack()Radiobutton3.pack()Radiobutton4.pack()                master.mainloop()