how to add a system font to a tkinter code example

Example 1: how to change font in tkinter

import tkinter.font as font

#create Font object
myFont = font.Font(family='Helvetica')

button = Button(parent, font=myFont)
#or
button = Button(parent)
button['font'] = myFont

Example 2: font in tkinter

import tkinter.font as TkFont

font = tkFont.Font ( option, ... )
# Exaple
helv36 = tkFont.Font(family="Helvetica",size=36,weight="bold")