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Y Fractal tree in Python using Turtle

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A fractal is a never-ending pattern. Fractals are infinitely complex patterns that are self-similar across different scales. They are created by repeating a simple process over and over in an ongoing feedback loop. Driven by recursion, fractals are images of dynamic systems – the pictures of Chaos.

In this article, we will draw a colorful Y fractal tree using a recursive technique in Python.


Output for depth level: (a) 14 (b) 12

Modules required

turtle: turtle library enables users to draw picture or shapes using commands, providing them with a virtual canvas. turtle comes with Python’s Standard Library. It needs a version of Python with Tk support, as it uses tkinter for the graphics.

Functions used:

  • fd(x) : draw the cursor forward by x pixels.
  • rt(x), lt(x) : rotates the facing direction of the cursor by x degrees to the right and left respectively.
  • colormode(): to change the colour mode to rgb.
  • pencolor(r, g, b): to set the colour of the turtle pen.
  • speed(): to set the speed of the turtle.

Approach :

  • We start by drawing a single ‘Y’ shape for the base(level 1) tree. Then both the branches of the ‘Y’ serve as the base of other two ‘Y’s(level 2).
  • This process is repeated recursively and size of the Y decreases as level increases.
  • Colouring of the tree is done level wise: darkest in the base level to lightest in the topmost.

In the implementation below, we will draw a tree of size 80 and level 7.

from turtle import *
# turning the turtle to face upwards
# the acute angle between
# the base and branch of the Y
angle = 30
# function to plot a Y
def y(sz, level):   
    if level > 0:
        # splitting the rgb range for green
        # into equal intervals for each level
        # setting the colour according
        # to the current level
        pencolor(0, 255//level, 0)
        # drawing the base
        # recursive call for
        # the right subtree
        y(0.8 * sz, level-1)
        pencolor(0, 255//level, 0)
        lt( 2 * angle )
        # recursive call for
        # the left subtree
        y(0.8 * sz, level-1)
        pencolor(0, 255//level, 0)
# tree of size 80 and level 7
y(80, 7)

Output :

Last Updated : 02 Jul, 2020
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