removing common elemets in a list

[saif.shakeel]

Hi,
Suppose i have a list v which collects some numbers,how do i
remove the common elements from it ,without using the set() opeartor.
Thanks

 

[Tim Golden]

Hi,
Suppose i have a list v which collects some numbers,how do i
remove the common elements from it ,without using the set() opeartor.

Is this a test? Why don't you want to use the set operator?
Anyway, you can just move things from one list into another
excluding those which are already moved:

<code>
numbers = [1, 2, 3, 3, 4, 4, 5]
unique_numbers = []
for n in numbers:
if n not in unique_numbers:
unique_numbers.append (n)

print unique_numbers
</code>

It won't be the fastest thing you could do, but it
does work. Using a dictionary would speed things up,
but then you're basically implementing a set using
a dictionary.

TJG

 

[Gary Herron]

Hi,
Suppose i have a list v which collects some numbers,how do i
remove the common elements from it ,without using the set() opeartor.
Thanks

Several ways, but probably not as efficient as using a set. (And why
don't you want to use a set, one wonders???)

>>> l = [1,2,3,1,2,1]

Using a set:
set([1, 2, 3])



Building the list element by element:
.... if e not in r:
.... r.append(e)
....[1, 2, 3]



Using a dictionary:

>>> d = dict(zip(l,l))
>>> d {1: 1, 2: 2, 3: 3}
>>> d.keys() [1, 2, 3]
>>>

 

[Carsten Haese]

Hi,
Suppose i have a list v which collects some numbers,how do i
remove the common elements from it ,without using the set() opeartor.
Thanks

If the list is sorted, you can weed out the duplicates with
itertools.groupby:

import itertools
L = [1,2,3,3,4,4,5]
[k for (k,_) in itertools.groupby(L, lambda x:x)]

[1, 2, 3, 4, 5]

HTH,

 

[John Zenger]

Hi,
Suppose i have a list v which collects some numbers,how do i
remove the common elements from it ,without using the set() opeartor.
Thanks

Submit this as your homework answer -- it will blow your TA's mind!

import base64
def uniq(v):
return
eval(base64.b64decode('c29ydGVkKGxpc3Qoc2V0KHYpKSxrZXk9bGFtYmRhIHg6di5pbmRleCh4KSk='),locals())

 

[Michael Bentley]

Submit this as your homework answer -- it will blow your TA's mind!

import base64
def uniq(v):
return
eval(base64.b64decode
('c29ydGVkKGxpc3Qoc2V0KHYpKSxrZXk9bGFtYmRhIHg6di5pbmRleCh4KSk='),local
s())

Nice! But I think he said he couldn't use set() ;-)

 

[janislaw]

Hi,
Suppose i have a list v which collects some numbers,how do i
remove the common elements from it ,without using the set() opeartor.
Thanks

There was a similar thread on polish python newsletter. The following
post displays 4 different approaches and explores timings:

http://groups.google.com/group/pl.comp.lang.python/msg/dc3618b18e63f3c9

Fortunately, python code is universal.