CODEWITHSUNDEEP
pythonlistpython-2.7
J.W.
J.W.

Reputation: 18181

Python sort is not working appropriately

I am trying to sort a list in python by one of it's property, however, it's not sorted correctly, any hint.

I try to print the value before and after sort, they are printing the same value.

 def kmeans_clustering(cluster_list, num_clusters, num_iterations):
    """
    Compute the k-means clustering of a set of clusters

    Input: List of clusters, number of clusters, number of iterations
    Output: List of clusters whose length is num_clusters
    """

    # initialize k-means clusters to be initial clusters with largest populations
    for idx in range(len(cluster_list)):
        print cluster_list[idx].total_population()

    print "sort.."
    sorted(cluster_list, key = lambda x: x.total_population(), reverse = True)

    for idx in range(len(cluster_list)):
        print cluster_list[idx].total_population()

Upvotes: 0

Views: 129

Answers (1)

falsetru
falsetru

Reputation: 369444

sorted returns a new sorted list, and does not sort the list in-place.

>>> x = [3, 2, 1]
>>> sorted(x)
[1, 2, 3]
>>> x
[3, 2, 1]

If you want to sort in-place, use list.sort instead:

>>> x.sort()
>>> x
[1, 2, 3]

Side note:

Instead of using the index to access each element, just iterate the list:

for cluster in cluster_list:
    print cluster.total_population()

Upvotes: 5

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