listerator clonage

[Alan McIntyre]

Cyril,

Here's some code that (I think) does what you want:

l = [1, 7, 3, 4, 3, 2, 1]
s, dups = set(), set()
for x in i:
     if x in s:
         dups.add(x)
     s.add(x)

print dups


I'm sure there are more elegant ways to do it, but this seemed to be the 
most straightforward way I could think of.

Hope this helps,
Alan McIntyre
ESRG LLC
http://www.esrgtech.com


Cyril BAZIN wrote:
> Hello, 
> 
> I want to build a function which return values which appear two or
> more times in a list:
> 
> So, I decided to write a little example which doesn't work:
> #l = [1, 7, 3, 4, 3, 2, 1]
> #i = iter(l)
> #for x in i:
> #    j = iter(i)
> #    for y in j:
> #        if x == y:
> #            print x
> 
> In thinked that the instruction 'j= iter(i)' create a new iterator 'j'
> based on 'i' (some kind of clone). I wrote this little test which show
> that 'j = iter(i)' is the same as 'j = i' (that makes me sad):
> 
> #l = [1, 7, 3, 4, 2]
> #i = iter(l)
> #j = iter(i)
> #k = i
> #i, j, k
> (<listiterator object at 0x02167B50>, <listiterator object at
> 0x02167B50>, <listiterator object at 0x02167B50>)
> 
> Just in order to test, I wrote these little test:
> #l = [1, 7, 3, 4, 2]
> #i = iter(l)
> #import pickle
> #j = pickle.loads(pickle.dumps(i))
> Traceback (most recent call last):
>   File "<input>", line 1, in ?
>   File "C:\Python24\lib\pickle.py", line 1386, in dumps
>     Pickler(file, protocol, bin).dump(obj)
>   File "C:\Python24\lib\pickle.py", line 231, in dump
>     self.save(obj)
>   File "C:\Python24\lib\pickle.py", line 313, in save
>     rv = reduce(self.proto)
>   File "C:\Python24\lib\copy_reg.py", line 69, in _reduce_ex
>     raise TypeError, "can't pickle %s objects" % base.__name__
> TypeError: can't pickle listiterator objects
> 
> #import copy
> #j = copy.copy(i)
> Traceback (most recent call last):
>   File "<input>", line 1, in ?
>   File "C:\Python24\lib\copy.py", line 95, in copy
>     return _reconstruct(x, rv, 0)
>   File "C:\Python24\lib\copy.py", line 320, in _reconstruct
>     y = callable(*args)
>   File "C:\Python24\lib\copy_reg.py", line 92, in __newobj__
>     return cls.__new__(cls, *args)
> TypeError: object.__new__(listiterator) is not safe, use listiterator.__new__()
> 
> So, I would like to know if there is a way to 'clone' a 'listiterator'
> object. I know that is possible in Java for example...
> 
> If it is impossible, have you better ideas to find duplicate entries
> in a list...
> 
> Thanks,
> 
> Cyril