I've implemented theK-Means clustering algorithm in Python2, and I wanted to know what remarks you guys could make regarding my code. I've included a small test set with 2D-vectors and 2 classes, but it works with higher dimensions and more classes. Here, it should sort all the elements starting with the same letters in the same classes (exceptak, with is quite in between).

What I'm interested in:

• Did I do somethingunpythonic?
• Are there unclear or unnecessary parts?
• What changes could drastically improve the code's performance?

from __future__ import print_functionfrom operator import add, subfrom _collections import defaultdictimport random as rdimport mathclass Element:    def __init__(self, idf, data, cls='ukn'):        self.idf = idf        self.data = data        self.cls = cls    def __str__(self):        return '%s: %s -> %s' % (str(self.idf), str(self.data), str(self.cls))    def eucl_dist_to(self, other):        diff = map(sub, self.data, other.data)        norm2 = math.sqrt(sum([math.pow(coord, 2) for coord in diff]))        return norm2def main():    test_data_tuple = [('aa', 1, 7), ('ab', 1, 8), ('ac', 1, 9), ('ba', 2, 1), ('bb', 2, 3), ('ad', 2, 8), ('ae', 2, 9),                   ('bc', 3, 2), ('bd', 3, 4), ('af', 3, 7), ('be', 4, 2), ('bf', 4, 3), ('ag', 4, 8),                   ('bg', 5, 1), ('bh', 5, 3), ('ah', 5, 6), ('bi', 6, 2), ('bj', 6, 4), ('ai', 6, 6), ('aj', 6, 7),                   ('bk', 7, 0), ('bl', 7, 2), ('bm', 7, 3), ('ak', 7, 5)]    test_data_elt = list()    for t in test_data_tuple:        test_data_elt.append(Element(t[0], tuple(t[1:])))    # test_data_elt.sort(key=lambda e: e.idf)    results = k_means(test_data_elt, 2, 5)def k_means(elts, nb_classes, nb_steps):    k = nb_classes    #init    centroids = list()    cls_content = defaultdict(list)    for cls_nb in range(k):        cls_name = 'class_'+str(cls_nb)        centroids.append(Element(cls_name, rd.choice(elts).data, cls='centroid'))        cls_content[cls_name] = list()    for itr in range(nb_steps):        # assign        cls_content.clear()        for elt in elts:            min_dist = float('inf')            for c in centroids:                dist = c.eucl_dist_to(elt)                if dist < min_dist:                    min_dist = dist                    best_class = c.idf            cls_content[best_class].append(elt)            elt.cls = best_class        # adjust        for c in centroids:            elts_in = list(cls_content[c.idf])            if len(elts_in) == 0:                sum_elts_data = 0            else:                sum_elts_data = list(elts_in[0].data)                for elt in elts_in[1:]:                    sum_elts_data = map(add, sum_elts_data, elt.data)                sum_elts_data[:] = [e / float(len(elts_in)) for e in sum_elts_data]                c.data = tuple(sum_elts_data)        print('\nIteration %d' % itr)        for c in centroids:            cls_name = c.idf            print('\n'+str(c))            for e in cls_content[cls_name]:                print(e)    return cls_contentif __name__ == '__main__':    main()

• \$\begingroup\$Did you consider usingscipy.cluster.vq.kmeans?\$\endgroup\$

  Gareth Rees

  – Gareth Rees

  2017-01-09 19:41:19 +00:00

  CommentedJan 9, 2017 at 19:41
• \$\begingroup\$Well, the point was to code the thing myself, I sure assumed that really good implementations already existed, I just wanted to have a go on my own :) Although I didn't know this one, thanks for having linked it!\$\endgroup\$

  BusyAnt

  – BusyAnt

  2017-01-10 11:30:03 +00:00

  CommentedJan 10, 2017 at 11:30
• 1
  \$\begingroup\$That's fine, I just wanted to check. (Take a look atthis answer for some implementation ideas.)\$\endgroup\$

  Gareth Rees

  – Gareth Rees

  2017-01-14 19:20:00 +00:00

  CommentedJan 14, 2017 at 19:20

1 Answer1

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