Binary Space Partitioning didactic example in Python

bsp.py

# -*- coding: utf-8 -*-
"""
Pure Python 3.6 example of doing binary space partioning for rectangles
Note the example is meant to be illustrative rather than performant, idiomatic or compact

Copyright 2019 Dustin Andrews

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

"""

import random
from collections import namedtuple

Rect = namedtuple('Rect', ['top','left', 'h', 'w'])

height = 20
width = 10

my_map = {}

for h in range(height):
    for w in range(width):
            my_map[f'{w},{h}'] = "00 "
            
def print_map(_map: dict):
    for h in range(height):
        for w in range(width):
            print(_map[f'{w},{h}'], end="")
        print()
    print()
        
    
def partition(rect :Rect, _map :dict, label: str):
    # Set all cells in rect to label
    return_map = _map.copy()    
    for x in range(rect.left, rect.w + rect.left):
        for y in range(rect.top, rect.h + rect.top):
            return_map[f'{x},{y}'] = f'{label}'
    return return_map
        
def select_partion(rect: Rect):
    # randomly slice the rect on the short axis
    # Small rect will be at least 1/4th the long axis
    # Return two smaller Rects
    top = rect.top
    left = rect.left
    h = rect.h
    w = rect.w
    top2 = top
    left2 = left
    h2 = h
    w2 = w
    
    if(h > w):
        # vertical
        onequarter = max(2,rect.h // 4)
        newsize = random.randint(onequarter, rect.h - onequarter)
        top2 = top + newsize
        h2 = h - newsize
        h = h - h2
    else:
        #horizontal
        onequarter = max(2,rect.w // 4)
        newsize = random.randint(onequarter, rect.w - onequarter)
        left2 = left + newsize
        w2 = w - newsize
        w = w - w2
        
    rect_one = Rect(top, left, h, w)
    rect_two = Rect(top2, left2, h2, w2)
    return rect_one, rect_two


def recursive_partition(rect: Rect):
    # Partition a rectangle into a number of smaller rectangles
    # Returns a tree of rectangles.
    
    if rect.h < 5 and rect.w < 5:
        return []
    else:
        r1, r2 = select_partion(rect)
        # use this line to return a tree struture
        children = [r1, r2, recursive_partition(r1) + recursive_partition(r2)]
        return children

def read_tree(tree : list):
    # Flatten branch tree to list
    branches=[]
    if type(tree) == type([]):
        for t in tree:  
            branches = read_tree(t) + branches
    else:
        return [tree]
    return branches

        

rect = Rect(0,0, height, width)
children = recursive_partition(rect)
branches = read_tree(children)
index = 1
nmap = my_map.copy()

# Show each partition in turn. Starting from the smallest
# and continuing until the largest 2
for b in branches:
    nmap = partition(b, nmap, f'{index:0{2}} ')
    print(index)
    index += 1
    print_map(nmap)
    print('q to stop, enter to continue')
    inp =  input()
    if inp == 'q':
        break