Filtering a Python list to uniques

[kellygreer1]

What is the best way to filter a Python list to its unique members?
I tried some method using Set but got some "unhashable " error.

lstone = [ 1, 2, 3, 3, 4, 5, 5, 6 ]
# how do i reduce this to
lsttwo = [ 1, 2, 3, 4, 5, 6 ]

Is there a page on this in the Python in a Nutshell or the Python
Cookbook?
Did I miss something?

Kelly Greer
kellygreer1@nos pam.com
change nospam to yahoo

[bearophileHUGS@lycos.com]

Re: Filtering a Python list to uniques

Kelly Greer:

What is the best way to filter a Python list to its unique members?

If Python is "batteries included", then an industrial-strength
unique() seems one of the most requested 'batteries' that's not
included :-) I feel that it's coming in Python 2.6/3.x. In the
meantime:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/502263

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/438599

Bye,
bearophile

[Mensanator]

Re: Filtering a Python list to uniques

On Mar 25, 6:30 pm, kellygreer1 <kellygre...@ya hoo.comwrote:

What is the best way to filter a Python list to its unique members?
I tried some method using Set but got some "unhashable " error.
>
lstone = [ 1, 2, 3, 3, 4, 5, 5, 6 ]
# how do i reduce this to
lsttwo = [ 1, 2, 3, 4, 5, 6 ]
>
Is there a page on this in the Python in a Nutshell or the Python
Cookbook?
Did I miss something?

I don't know, the set() soution worked for me.

>>lstone = [1,2,3,3,4,5,5,6]
>>setone = set(lstone)
>>lsttwo = list(setone)
>>lstone

[1, 2, 3, 3, 4, 5, 5, 6]

>>setone

set([1, 2, 3, 4, 5, 6])

>>lsttwo

[1, 2, 3, 4, 5, 6]

>
Kelly Greer
kellygre...@nos pam.com
change nospam to yahoo

[Raymond Hettinger]

Re: Filtering a Python list to uniques

On Mar 25, 4:30 pm, kellygreer1 <kellygre...@ya hoo.comwrote:

What is the best way to filter a Python list to its unique members?
I tried some method using Set but got some "unhashable " error.
>
lstone = [ 1, 2, 3, 3, 4, 5, 5, 6 ]
# how do i reduce this to
lsttwo = [ 1, 2, 3, 4, 5, 6 ]

If the elements are hashable, try this:
lsttwo = sorted(set(lsto ne))
If not hashable, try:
lsttwo = [k for k,v in itertools.group by(sorted(lston e))]


Raymond

[hellt]

Re: Filtering a Python list to uniques

On 26 ÍÁÒ, 02:30, kellygreer1 <kellygre...@ya hoo.comwrote:

What is the best way to filter a Python list to its unique members?
I tried some method using Set but got some "unhashable " error.
>
lstone = [ 1, 2, 3, 3, 4, 5, 5, 6 ]
# how do i reduce this to
lsttwo = [ 1, 2, 3, 4, 5, 6 ]
>
Is there a page on this in the Python in a Nutshell or the Python
Cookbook?
Did I miss something?
>
Kelly Greer
kellygre...@nos pam.com
change nospam to yahoo

or just look this thread for a fastest solution

http://groups.google.com/group/comp.lang.python/browse_frm/thread/7091898414444310/af8961f1ed91ccea?lnk=gst&q=duplicates#af8961f1ed91ccea

[kellygreer1]

Re: Filtering a Python list to uniques

On Mar 26, 5:45 am, hellt <Dodin.Ro...@gm ail.comwrote:

On 26 ÍÁÒ, 02:30,kellygree r1<kellygre...@ yahoo.comwrote:
>

What is the best way to filter a Python list to its unique members?
I tried some method using Set but got some "unhashable " error.

>

lstone = [ 1, 2, 3, 3, 4, 5, 5, 6 ]
# how do i reduce this to
lsttwo = [ 1, 2, 3, 4, 5, 6 ]

>

Is there a page on this in the Python in a Nutshell or the Python
Cookbook?
Did I miss something?

>

Kelly Greer
kellygre...@nos pam.com
change nospam to yahoo

>
or just look this thread for a fastest solutionhttp://groups.google.c om/group/comp.lang.pytho n/browse_frm/thread/709...

How come the Set() thing seems to work for some people and I get the
'unhashable' error?

How do you test for 'membership' on a dictionary?

# where tmp is the non-unique list
# dct is a dictionary where each unique key will be tied to a count
(the value)
# for testing I was setting the count to 0
for v in tmp:
if not v in dct: dct[v] = 0

# I get unhashable error here.
# Even if I write it.

for v in tmp:
if not v in dct.keys(): dct[v] = 0

What am I missing?

Thanks,
Kelly

[Jerry Hill]

Re: Filtering a Python list to uniques

On Wed, Mar 26, 2008 at 2:50 PM, kellygreer1 <kellygreer1@ya hoo.comwrote:

How come the Set() thing seems to work for some people and I get the
'unhashable' error?
>
How do you test for 'membership' on a dictionary?
>
# where tmp is the non-unique list
# dct is a dictionary where each unique key will be tied to a count
(the value)
# for testing I was setting the count to 0
for v in tmp:
if not v in dct: dct[v] = 0
>
# I get unhashable error here.
# Even if I write it.
>
for v in tmp:
if not v in dct.keys(): dct[v] = 0
>
What am I missing?

Some of the elements of tmp are unhashable. Unhashable items can't be
the keys of a dictionary or members of a set. I don't think you've
said anywhere in the thread what these items are, you just started out
with an example of a list of integers. Do you believe the elements in
tmp are integers? If so, try the following -

for v in tmp:
print type(v), repr(v), hash(v)

and let us know what it spits out.

--
Jerry