import numpy as np


def neighbors(n, x):
return ([x+n] if x+n<n*n else []) + \
       ([x-n] if x>=n    else []) + \
       ([x-1] if x%n>0   else []) + \
       ([x+1] if x%n<n-1 else [])


def decompose(n, g):
    if n*n<g: return []
    spawn = [i for i in np.random.choice(n*n, g, replace=False)]
    grid = [0] * (n*n)
    nbhd = [[] for _ in range(g)]
    occupied = set(spawn)
    for i,x in enumerate(spawn): 
        grid[x] = i+1
        for u in neighbors(n, x): 
            if u not in occupied: nbhd[i].append(u)
    grp = 0
    while len(occupied) < len(grid):
        ns = nbhd[grp][:]
        d = 0
        for j,nb in enumerate(ns): 
            if nb in occupied: del nbhd[grp][j-d] ; d+=1
        if nbhd[grp] != []:
            r = np.random.randint(len(nbhd[grp]))
            c = nbhd[grp][r]
            del nbhd[grp][r]
            grid[c] = grp + 1
            occupied.add(c)
            for nb in neighbors(n, c):
                if nb not in occupied:
                    nbhd[grp].append(nb)
            # for i in range(5): print(grid[5*i:5*i+5])
            # print()
            # print(nbhd)
            # print()
            # print('occupied: ', occupied)
        grp = (grp + 1) % g
    return grid

z = decompose(10,5)
for i in range(10): print(z[10*i:10*(i+1)])


def partitiongrid(n, gr):
    g = decompose(n, gr)
    w = 2*n-1
    print(' _' * n)
    s = ''
    for i in range(n):
        s = '|'
        for j in range(n-1):
            s += '_' if i == n-1 or g[n*i + j] != g[n*(i+1)+j] else ' '
            s += '|' if g[n*i + j] != g[n*i+1+j] else ' '
        s += '_' if i == n-1 or g[n*i + n-1] != g[n*(i+1)+n-1] else ' '
        s += '|'
        print(s)
        s = ''
    print()
    # for i in range(n): print(g[n*i:n*(i+1)])
partitiongrid(15, 10)

->   _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
    |    _|        _ _ _|         |
    |   |      _ _|     |         |
    |   |     |_        |_ _      |
    |   |_ _ _ _|          _|_    |
    |  _|  _|   |_ _ _ _ _|   |_  |
    | |   |_ _ _       _|       |_|
    | |_        |    _|           |
    |   |       |_  |_            |
    |_ _|  _ _ _ _|   |_ _ _     _|
    |   |_|   |  _ _ _ _ _| |_ _| |
    |         |_|         |       |
    |         |           |       |
    |         |          _|       |
    |         |         |         |
    |_ _ _ _ _|_ _ _ _ _|_ _ _ _ _| (0.0s)