How would you group/cluster these three areas in arrays in python?

Question

So you have an array

1
2
3
60
70
80
100
220
230
250

For a better understanding:

Answer 1

This is a simple algorithm implemented in python that check whether or not a value is too far (in terms of standard deviation) from the mean of a cluster:

from math import sqrt

def stat(lst):
    """Calculate mean and std deviation from the input list."""
    n = float(len(lst))
    mean = sum(lst) / n
    stdev = sqrt((sum(x*x for x in lst) / n) - (mean * mean)) 
    return mean, stdev

def parse(lst, n):
    cluster = []
    for i in lst:
        if len(cluster) <= 1:    # the first two values are going directly in
            cluster.append(i)
            continue

        mean,stdev = stat(cluster)
        if abs(mean - i) > n * stdev:    # check the "distance"
            yield cluster
            cluster[:] = []    # reset cluster to the empty list

        cluster.append(i)
    yield cluster           # yield the last cluster

This will return what you expect in your example with 5 < n < 9:

>>> array = [1, 2, 3, 60, 70, 80, 100, 220, 230, 250]
>>> for cluster in parse(array, 7):
...     print(cluster)
[1, 2, 3]
[60, 70, 80, 100]
[220, 230, 250]