[Tutor] Question about style

[Jose Amoreira]

Hello
I wrote a function that, given a list of numbers, finds clusters of 
values by proximity and returns a reduced list containing the centers of 
these clusters. However, I find it rather unclear. I would appreciate 
any comments on how pythonic my function is and suggestions to improve 
its readability.
The function is:

def aglomerate(x_lst, delta=1.e-5):
     clusters = [] #list of pairs [center, number of clustered values]
     for x in x_lst:
         close_to = [abs(x - y) < delta for y,_ in clusters]
         if any(close_to):
             # x is close to a cluster
             index = close_to.index(True)
             center, n = clusters[index]
             #update the cluster center including the new value,
             #and increment dimension of cluster
             clusters[index] = (n * center + x)/(n+1), n+1
         else:
             # x does not belong to any cluster, create a new one
             clusters.append([x,1])
     # return list with centers
     return [center for center, _ in clusters]

Examples:
1. No clusters in x_lst:
In [52]: aglomerate([1., 2., 3., 4.])
Out[52]: [1.0, 2.0, 3.0, 4.0]

2. Some elements in x_lst are equal:
In [53]: aglomerate([1., 2., 1., 3.])
Out[53]: [1.0, 2.0, 3.0]

3. Some elements in x_lst should be clustered:
In [54]: aglomerate([1., 2., 1.1, 3.], delta=0.2)
Out[54]: [1.05, 2.0, 3.0]

So, the function seems to work as it should, but can it be made more 
readable?

Thanks for any help.
Ze