command method of tkinter checkbutton works only while instantiates class

Question

I have created a class of tkinter where checkbutton is created while calling function checkbutton_create method. It is invocating happens during initialization of class inside loop.

for k,v in df.items():
    self.checkbutton_create(k)

I from start do not know how many checkbuttons will be created, it is depended on user's input inside file.

I have put a command function which will see state change in any of checkbutton and if it is 1 it will append the text of checkbutton to class list cls_list_checkbtn = []

class UsrApp():
    df=None
    cls_list_checkbtn = []
    def __init__(self):
        self.root=Tk()
        self.root.title('Gmail Rotater Bulk EmailSender')
        #frame for email checkbuttons
        self.frm_checkbuttons=Frame(master=self.root,relief=SUNKEN,borderwidth=3)
        self.frm_checkbuttons.pack(side='top',expand=YES,fill=X)
        #checkbutton instantiations
        df=pd.read_json('Email_Addresses/emailaddresses.json')
        self.list_checkbtn=[]
        self.dict_emails={}
        self.count=0
        for k,v in df.items():
            self.checkbutton_create(k)
            self.dict_emails[self.count]=k
            self.count +=1


    def checkbutton_create(self,txt):
        self.wdgt_var = IntVar()
        self.wdg_checkbutton = tkinter.Checkbutton(master=self.frm_checkbuttons, text=txt, variable=self.wdgt_var, command=self.checkbtn_add_list_text_values(txt,self.wdgt_var.get()))
        self.wdg_checkbutton.pack(side='left',expand=YES,fill=X)

    def checkbtn_add_list_text_values(self,txt,var_text):
        print(var_text)
        if var_text==1:
            self.list_checkbtn.append(txt)
            self.cls_list_checkbtn(txt)

I slightly changed code, added command to checkbuttons which have to fixture a state change in checkbutton value. But it only works when class is instantiated..

I was expecting every time state of checkbutton changes function checkbtn_add_list_text_values fixture it and append text value to list. But it only fixture when class is instantiated