Turtle Event Lisener

turtle.lisen()
turtle.onkey(fun #create a function with parameter,key #set a key in alphabet & icons)
2.higher oder funtion
one funtion works with another funtion 
eg :def calculation(n1, n2, funtion)
    return funtion(n1, n2)


    calculation(1, 5, add)
add is funtion 

#python commonly use but other language not
3.