A Fun Python Turtle YouTube Playlist

"""Draw a fractal tree."""

import random
from turtle import Screen, Turtle, _Screen
from typing import Optional, Tuple

RGBColor = Tuple[float, float, float]

COLOR_CANVAS_DEFAULT: RGBColor = (232 / 255, 210 / 255, 210 / 255)
COLOR_PEN_DEFAULT: RGBColor = (94 / 255, 71 / 255, 69 / 255)
COLOR_SKY_LIGHT: RGBColor = (0.53, 0.81, 0.92)
COLOR_SKY_DARK: RGBColor = (0.008, 0.043, 0.059)
COLOR_TRUNK_BASE: RGBColor = (0.26, 0.16, 0.11)
COLOR_TRUNK_LIGHT: RGBColor = (0.96, 0.86, 0.81)


def set_theme(
    screen: _Screen,
    turtle: Turtle,
    canvas_width=1000,
    canvas_height=1000,
    canvas_color=COLOR_CANVAS_DEFAULT,
    pen_color=COLOR_PEN_DEFAULT,
    thickness=1,
    speed_value=0,
    tracer_value=0,
    hide_turtle=True,
):
    """Set properties for the current drawing."""
    screen.setup(canvas_width, canvas_height)
    screen.bgcolor(canvas_color)
    turtle.color(pen_color)
    turtle.width(thickness)
    turtle.speed(speed_value)
    screen.tracer(tracer_value)

    if hide_turtle:
        turtle.hideturtle()


def draw_leaf(turtle: Turtle):
    """Draw a single leaf."""
    leaf_color = (
        random.uniform(0.25, 0.5),
        random.uniform(0.5, 0.75),
        random.uniform(0.25, 0.5),
    )
    turtle.color(leaf_color)
    turtle.begin_fill()
    turtle.circle(4.0)
    turtle.end_fill()
    turtle.color(COLOR_TRUNK_BASE)


def grow(turtle: Turtle, length, decrease, angle, noise=0):
    """Draw a single tree segment."""
    if length <= 8:
        draw_leaf(turtle)
        return

    length_factor = length / 10
    trunk_color = lighten_trunk(length_factor)

    turtle.color(trunk_color)
    turtle.width(length_factor)
    turtle.forward(length)
    new_length = length * decrease

    if noise > 0:
        new_length *= random.uniform(0.9, 1.1)

    angle_l = angle + random.gauss(0, noise)
    angle_r = angle + random.gauss(0, noise)
    turtle.left(angle_l)
    grow(turtle, new_length, decrease, angle, noise)
    turtle.right(angle_l)
    turtle.right(angle_r)
    grow(turtle, new_length, decrease, angle, noise)
    turtle.left(angle_r)
    turtle.backward(length)


def fit_color(
    rgb: RGBColor,
    minimum_rgb: Optional[RGBColor] = None,
    maximum_rgb: Optional[RGBColor] = None,
):
    "Ensure color fits within an allowed RGB range."
    fitted_color = rgb

    if minimum_rgb:
        fitted_color = (
            min(minimum_rgb[0], fitted_color[0]),
            min(minimum_rgb[1], fitted_color[1]),
            min(minimum_rgb[2], fitted_color[2]),
        )
    if maximum_rgb:
        fitted_color = (
            max(maximum_rgb[0], fitted_color[0]),
            max(maximum_rgb[1], fitted_color[1]),
            max(maximum_rgb[2], fitted_color[2]),
        )

    return fitted_color


def draw_sky(screen: _Screen, turtle: Turtle):
    """Draw a fractured sky."""
    size = 30
    noise = 0.0
    x_edge = screen.window_width() // 2
    y_edge = screen.window_height() // 2

    for y in range(-y_edge, y_edge, size):
        for x in range(-x_edge, x_edge, size):
            # move to the location
            turtle.penup()
            turtle.goto(x, y)

            # rotate
            angle = random.uniform(-noise, noise)

            if noise:
                noise_factor = 1 / (y_edge - y) * 100
                sky_color = darken_sky(noise_factor)
            else:
                sky_color = COLOR_SKY_DARK

            turtle.pendown()
            turtle.color(COLOR_SKY_DARK, sky_color)
            turtle.begin_fill()
            turtle.right(angle)

            # draw square
            for i in range(4):
                turtle.forward(size)
                turtle.right(90)

            turtle.left(angle)
            turtle.end_fill()
        noise += 1


def draw_tree(screen: _Screen, turtle: Turtle):
    """Draw one tree."""
    # start at the bottom edge, off-center for visual interest
    y_edge = screen.window_height() / 2
    trunk_x = screen.window_width() / 4 * -1
    turtle.penup()
    turtle.goto(trunk_x, -y_edge)
    turtle.left(90)
    turtle.pendown()
    grow(turtle, 140, 0.8, 30, noise=10)


def darken_sky(noise_factor: float):
    """Manages a gradual darkening of sky squares."""
    sky_color = tuple(value - noise_factor for value in COLOR_SKY_LIGHT)

    return fit_color(sky_color, maximum_rgb=COLOR_SKY_DARK)


def lighten_trunk(length_factor):
    """Manages a gradual lightening of the trunk's color."""
    color_factor = 1 / length_factor
    trunk_color = tuple(value + color_factor for value in COLOR_TRUNK_BASE)

    return fit_color(trunk_color, minimum_rgb=COLOR_TRUNK_LIGHT)


def main():
    """Draw a tree."""
    screen = Screen()
    turtle = Turtle()
    set_theme(screen, turtle, canvas_width=1920, canvas_height=1080)
    draw_sky(screen, turtle)
    draw_tree(screen, turtle)
    screen.tracer(True)
    screen.exitonclick()


if __name__ == "__main__":
    main()