distance_matrix_trick.py

import numpy as np
from itertools import combinations


def distance_loop(X):
    N, M = X.shape
    dist = np.zeros((N, N))
    for i, j in combinations(range(N), 2):
        xi = X[i]
        xj = X[j]
        dist[i, j] = dist[j, i] = ((xi - xj) ** 2).sum()
    return dist