Unique Elements in a List

[superprad]

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.
Probably something like a Hash Table approach!!
I would like to get this done without unnecessary overhead.And the list
could be essentially anything strings,floats, int etc...

Or is it already avaliable as an attr to a list or an array?
I dont remember seeing anything like that.

[superprad]

OK I need to be more clear I guess!Unique Elements I mean, elements
that are non repeating. so in the above list 0.4, 0.9 are unique as
they exist only once in the list.

[runes]

This is not the most beautiful idiom, but it works...

d = {}
for k in data:
try:
d[k] += 1
except:
d[k] = 1

for k,v in d.items():
if v == 1:
print k

[Roie Kerstein]

su*******@gmail .com wrote:

Is there an easy way to grab the Unique elements from a list?

Yes.
The set data type.
Look in the reference of python 2.4.
--
Best regards
Roie Kerstein

[James Stroud]

On Monday 09 May 2005 03:15 pm, su*******@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.
Probably something like a Hash Table approach!!
I would like to get this done without unnecessary overhead.And the list
could be essentially anything strings,floats, int etc...

Or is it already avaliable as an attr to a list or an array?
I dont remember seeing anything like that.

from sets import Set

data = [0.1,0.5,0.6,0.4 ,0.1,0.5,0.6,0. 9]

[x for x in Set(data) if data.count(x) == 1]

--
James Stroud
UCLA-DOE Institute for Genomics and Proteomics
Box 951570
Los Angeles, CA 90095

http://www.jamesstroud.com/

[bearophileHUGS]

runes:

d = {}
for k in data:
try:
d[k] += 1
except:
d[k] = 1

for k,v in d.items():
if v == 1:
print k

For this problem, if duplicated keys are common enough, this version is
probably the faster.

With this *different* problem, it seems that sometimes the faster
solution is using "in":
http://pyalot.blogspot.com/2005/04/d...ary-speed.html

Bye,
Bearophile

[Michael J. Fromberger]

In article <11************ **********@z14g 2000cwz.googleg roups.com>,
"su*******@gmai l.com" <su*******@gmai l.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.
Probably something like a Hash Table approach!!
I would like to get this done without unnecessary overhead.And the list
could be essentially anything strings,floats, int etc...

Or is it already avaliable as an attr to a list or an array?
I dont remember seeing anything like that.

From your comments downthread, it seems you want to find those elements
of the input sequence which occur exactly once, and return not only
these elements, but also their positions.

One reasonable solution might be as follows:

def unique_elts(seq ):
elts = {}
for pos, elt in enumerate(seq):
elts.setdefault (elt, []).append(pos)

return [ (x, p[0]) for (x, p) in elts.iteritems( )
if len(p) == 1 ]

This returns a list of tuples of the form (x, pos), where x is an
element of seq that occurs exactly once, and pos is its index in the
original sequence. This implementation traverses the input sequence
exactly once, and requires storage proportional to the length of the
input.

-M

--
Michael J. Fromberger | Lecturer, Dept. of Computer Science
http://www.dartmouth.edu/~sting/ | Dartmouth College, Hanover, NH, USA

[Aahz]

In article <11************ **********@f14g 2000cwb.googleg roups.com>,
runes <ru*********@gm ail.com> wrote:

This is not the most beautiful idiom, but it works...

d = {}
for k in data:
try:
d[k] += 1
except:
d[k] = 1

for k,v in d.items():
if v == 1:
print k

Only if "works" does not include "order preserving".
--
Aahz (aa**@pythoncra ft.com) <*> http://www.pythoncraft.com/

"And if that makes me an elitist...I couldn't be happier." --JMS

[Paul Rubin]

"su*******@gmai l.com" <su*******@gmai l.com> writes:

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]

Untested: here's an iterator that gives you the index and value,
without reordering. Uses dicts instead of sets for backwards compatibility.

def unique_elements (data):
seen = {}
for n,x in data:
if x not in seen:
seen[x] = 1
yield n,x

[Rune Strand]

You're right. I somehow missed the index part :-o. It's easy to fix
though.