Drawing of Python overlay equilateral triangle

Python Language Programming Basics Exercise 2.5

ImportTurtledefDrawtriangle (Num,len,flag):#flag is used to adjust the direction of the triangle.Flag*=-1Len/=2if(num==1):        if(flag==1): Turtle.left (60) turtle.fd (len) turtle.right (120) turtle.fd (len) turtle.right (120) turtle.fd (len) turtle.left (120)        Else: Turtle.right (60) turtle.fd (len) turtle.left (120) turtle.fd (len) turtle.left (120) turtle.fd (len) turtle.right (120)    Else:        if(flag==1): Turtle.left (60) turtle.fd (Len/2) Num=num-1Turtle.right (60) Drawtriangle (Num,len,flag) turtle.fd (Len/2) Turtle.right (120) turtle.fd (len) turtle.right (120) turtle.fd (len) turtle.left (120)#Note the angle that the brush returns during recursion        Else: Turtle.right (60) turtle.fd (Len/2) Num=num-1Turtle.left (60) Drawtriangle (Num,len,flag) turtle.fd (Len/2) Turtle.left (120) turtle.fd (len) turtle.left (120) turtle.fd (len) turtle.right (120)#Note the angle that the brush returns during recursion        defMain (): Turtle.setup (600,600, 200, 200) Turtle.pendown () Turtle.speed (2) Turtle.pensize (5) Drawtriangle (5,512,-1) Turtle.hideturtle ()#Hide Brush iconMain () Turtle.done ()#which returns after the main loop exits do not know what the meaning, anyway can let the window stop (welcome comment tell me AH)?

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Drawing of Python overlay equilateral triangle