python checkbox multiple select

now, how i get multiple check in the same time? i cant select 2 or 3 or 4 checkbox in the same time,it only allows me 1 select for time

def check_appointments():
    print(var.get())

def checkbox():
    contacto = Contacto()
    arreglo = contacto.buscar(1)
    m=2
    n=1

    for c in arreglo:
        m=m+1
        n=n+1
        for r in range(n,m):
            for co in range(1, 9):
                if co==5:
                    cell = Entry(master, width=10,justify='center',font=("Calibri",11),disabledbackground="cadetblue",disabledforeground="black")
                    cell.grid(padx=1, pady=1, row=r, column=co)
                    t=add_date(c[4],1)
                    cell.insert(END,t)
                else: 
                    cell = Entry(master, width=15,justify='center',font=("Calibri",11),disabledbackground="cadetblue",disabledforeground="black")                   
                    cell.insert(END,c[co-1])

                cell.grid(padx=1, pady=1, row=r, column=co)

                cell.config (state = DISABLED )
                cb = Checkbutton(master, command=check_appointments, variable=var, onvalue=c[0],offvalue="0")
                cb.grid( row=r, column=0)                           
                cb.deselect()
master=Tk()
var = StringVar()
cajaB = StringVar()
checkbox()
master.mainloop()

check image