Generates longwinded street-like patterns with a few T-junctions and rarely a deadend. Not fixed for unconnected, circular roads. Let's just pretend they're 'gated communities'.

wang.py

#!/usr/bin/env python
"""
ASCII wang tile generator
written by @paniq (2011/3/26)

Generates longwinded street-like patterns with a few T-junctions and rarely
a deadend. Not fixed for unconnected, circular roads. Let's just pretend they're
'gated communities'.

Example output:
                                                            
 %XX%XX%XX%XX%  %XX%  %XX%XX%  %XX%  %XX%XX%  %XX%  %XX%  % 
 X           X  X  X  X     X  X  X  X     X  X  X  X  X  X 
 X           X  X  X  X     X  X  X  X     X  X  X  X  X  X 
 %XX%XX%  %XX%  %  %  %  %XX%  %  %XX%  %XX%  %  %XX%  %  % 
       X  X     X  X  X  X     X        X     X  X     X  X 
       X  X     X  X  X  X     X        X     X  X     X  X 
 %XX%  %  %  %XX%  %  %  %  %XX%  %XX%  %XX%  %  %XX%XX%  % 
 X  X  X  X  X     X  X  X  X     X  X     X  X           X 
 X  X  X  X  X     X  X  X  X     X  X     X  X           X 
 %  %XX%  %XX%  %XX%  %XX%  %XX%XX%  %XX%  %  %XX%  %XX%XX% 
 X  X           X                    X  X  X     X  X       
 X  X           X                    X  X  X     X  X       
 %XX%  %XX%  %XX%  %XX%XX%  %XX%XX%XX%  %  %  %XX%  %XX%  % 
       X  X  X     X     X  X           X  X  X     X  X  X 
       X  X  X     X     X  X           X  X  X     X  X  X 
 %XX%  %  %  %XX%XX%  %XX%XX%  %XX%  %XX%  %  %  %XX%  %XX% 
 X  X  X  X           X        X  X  X     X  X  X          
 X  X  X  X           X        X  X  X     X  X  X          
 %  %XX%  %  %XX%  %XX%  %XX%  %XX%  %XX%  %  %XX%  %XX%XX% 
 X        X  X  X  X     X  X        X  X  X        X     X 
 X        X  X  X  X     X  X        X  X  X        X     X 
 %XX%XX%  %XX%  %  %XX%  %  %XX%XX%  %  %XX%  %XX%  %  %XX% 
       X        X     X  X        X  X        X  X  X  X    
       X        X     X  X        X  X        X  X  X  X    
 %XX%XX%  %XX%XX%  %XX%  %XX%  %XX%  %XX%XX%XX%XX%  %XX%  % 
 X        X        X        X  X     X                 X  X 
 X        X        X        X  X     X                 X  X 
 %XX%XX%XX%  %XX%XX%XX%XX%XX%  %XX%XX%XX%XX%XX%XX%XX%XX%  % 

"""

import random

# map dimension
NX,NY = 20,10

class Tile:
    #edge order:
    # +X +Y -X -Y
    edges = list('****')
    pattern = None

    @classmethod
    def generate(cls, in_edges):
        pattern = [' ']*9
        
        walls = set()
        edges = ['f']*4
        def add_wall(i):
            if i in walls:
                return
            x,w = {
                0 : (5,'X'),
                1 : (1,'X'),
                2 : (3,'X'),
                3 : (7,'X'),
            }[i]
            edges[i] = 'w'
            pattern[x] = w
            walls.add(i)
            
        choices = set()
        for i,e in enumerate(in_edges):
            if e == 'w':
                add_wall(i)
            elif e == '*':
                choices.add(i)

        rand = random.random()
        if rand < 0.05: # 5% chance for T-junction
            c = 3
        elif rand < 0.01: # 1% change for deadend
            c = 1
        else:
            # simple connection
            c = 2
            
        while len(walls) < c and choices:
            i = random.choice(list(choices))
            choices.discard(i)
            add_wall(i)
        
        if walls:
            pattern[4] = '%'
                
        tile = cls()
        tile.pattern = pattern
        tile.edges = edges
        return tile

class Map(dict):
    def get_tile(self, key):
        x,y = key
        if x < 0 or x >= NX or y < 0 or y >= NY:
            tile = Tile()
            tile.edges = list('ffff')
            return tile
        return self.get(key, None) or Tile()

    def get_edges(self, x,y):
        return self.get_tile((x,y)).edges

    @classmethod
    def generate(cls):
        map = cls()
        for y in range(NY):
            for x in range(NX):
                map[(x,y)] = Tile.generate([
                    map.get_edges(x+1,y)[2],
                    map.get_edges(x,y-1)[3],
                    map.get_edges(x-1,y)[0],
                    map.get_edges(x,y+1)[1]
                ])
        return map
    
    def __str__(self):
        output = ''
        for y in range(NY):
            rows = ['','','']
            for x in range(NX):
                tile = self.get_tile((x,y))
                for l in range(3):
                    rows[l] += ''.join(tile.pattern[l*3:l*3+3])
                    
            output += '\n'.join(rows) + '\n'
        return output
            
if __name__ == '__main__':
    print(Map.generate())