Tree grow simulator on python3 with tk

tree_grow.py

#!/usr/bin/env python3

# tree grow simulator on python3 with tk

import tkinter as tk
from random import randint
from enum import Enum


class TreePart(Enum):
    none = 0
    trunk = 1
    branch = 2
    leaf = 3


class TreeCell(object):
    def __init__(self, x, y, size=2, part=TreePart.trunk):
        self.x = x
        self.y = y
        self.size = size
        self.part = part

    @property
    def color(self):
        if self.part is TreePart.trunk or self.part is TreePart.branch:
            return 'saddle brown'
        elif self.part is TreePart.leaf:
            return 'green'

    def fork(self):
        if self.part is TreePart.trunk:
            return TreeCell(self.x + randint(-1, 1), self.y - randint(0, 2), size=self.size, part=TreePart.trunk)
        elif self.part is TreePart.branch:
            return TreeCell(self.x + randint(-5, 5), self.y - randint(0, 2), size=self.size, part=TreePart.branch)
        elif self.part is TreePart.leaf:
            return TreeCell(self.x + randint(-8, 8), self.y - randint(0, 2), size=self.size, part=TreePart.leaf)


class TreeApp(tk.Tk):
    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)
        # configure main window
        self.wm_title('Tree grow')
        # cells
        self.cells = [TreeCell(399, 600), TreeCell(400, 600), TreeCell(401, 600)]
        # canvas
        self.can = tk.Canvas(self, bg='grey', width=800, height=600)
        self.can.pack()
        # create text
        self.cell_txt = self.can.create_text(680, 80, text='%d cells' % len(self.cells), font=('verdana', 10, 'bold'))
        # launch tree grow
        self.grow()

    def grow(self):
        # do a cell duplicate on last 100 new cells
        for c in list(self.cells[-100:]):
            # new cell is a fork of current cell
            nc = c.fork()
            # type change for level: first is trunk then branch and finally leaf
            if 450 < nc.y <= 600:
                nc.part = TreePart.trunk
            elif 200 < nc.y <= 450:
                nc.part = TreePart.branch
            elif nc.y <= 200:
                nc.part = TreePart.leaf
            # add new cell
            self.cells.append(nc)
            # draw new cell
            self.add_cell(nc)
        # update text
        self.can.itemconfig(self.cell_txt, text='%d cells' % len(self.cells))
        # refresh
        self.after(200, func=self.grow)

    def clear(self):
        self.can.delete('all')

    def add_cell(self, cell):
        """
        Draw a cell on canvas

        :param cell: cell to draw
        :type cell: TreeCell
        """
        r = cell.size/2
        (x0, y0) = (cell.x - r, cell.y - r)
        (x1, y1) = (cell.x + r + 1, cell.y + r + 1)
        self.can.create_oval(x0, y0, x1, y1, fill=cell.color)


if __name__ == '__main__':
    # main Tk App
    app = TreeApp()
    app.mainloop()