Unique Elements in a List

[Steven Bethard]

superprad at gmail.com wrote:
> Is there an easy way to grab the Unique elements from a list?
> For Example:
> data = [0.1,0.5,0.6,0.4,0.1,0.5,0.6,0.9]
> 
> what I am looking for is the unique elements 0.4 and 0.9 with their
> index from the list.

This is basically the same as Fredrik Lundh's solution, but here it is 
anyway:

py> def f(lst):
...     counts = dicttools.counts(lst)
...     return [(i, elem)
...             for i, elem in enumerate(lst)
...             if counts[elem] == 1]
...
py> f([0.1,0.5,0.6,0.4,0.1,0.5,0.6,0.9])
[(3, 0.40000000000000002), (7, 0.90000000000000002)]

Where dicttools.counts is defined as:

def counts(iterable, key=None):
     result = {}
     for item in iterable:
         # apply key function if necessary
         if key is None:
             k = item
         else:
             k = key(item)
         # increment key's count
         try:
             result[k] += 1
         except KeyError:
             result[k] = 1
     return result

(I use this so often that I have a module called dicttools to hold it. 
You don't actually need the key= argument for your problem, but I just 
copied the code directly.)

STeVe