from PIL import Image, ImageDraw
from functools import reduce
 
# ニュートン法はfunctools.reduceを使った方がシンプルに書ける
def newton(x):
    return reduce(lambda j, i: j - (j**3 - 1) / (3 * j**2), range(10), x)
 
def plot(draw, s):
    hs = s // 2
    red = (255, 0, 0)
    green = (0, 255, 0)
    blue = (0, 0, 255)
    # ローカル関数fooを定義する
    def foo(x, y):
        nonlocal s, hs
        z = newton(complex(x - hs + 0.5, -y + hs + 0.5) / s * 4)
        # 条件分岐「文」ではなく、条件分岐「式」に慣れよう
        return red if z.real > 0 else green if z.real < 0 and z.imag > 0 else blue
    # Pythonではfor文を使うよりリスト内包表記を使った方がスマートだ
    [draw.rectangle([x, y, x + 1, y + 1], fill = foo(x, y)) for y in range(s)\
     for x in range(s)]
 
# スクリプトとして起動する
if __name__ == '__main__':
    size = 512
    img = Image.new('RGB', (size, size))
    plot(ImageDraw.Draw(img), size)
    img.show()
    img.save('img.png')
 
 

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