def quitar_dup(lista):

    for item in lista:

        item.reverse()

        if item in lista:
            lista.remove(item)

    return lista

L=[[1,2],[1,3],[2,1],[3,1]]

print quitar_dup(L)  #res: [[1, 3], [3, 1]]

>>> def add(a, l):
        if a not in l:
            l+=[a]
        return l 
    
>>> L=[1,2,3]
>>> add(1,L)

>>> add(4,L)

>>> L

>>> def add(a, l=[]):
        if a not in l:
            l+=[a]
        return l
>>> add(1)

>>> add(2)

>>> add(3,[])

>>> add(4)

fns=[]

for i in range(5):
    fns.append( lambda x: x+i)

print fns[1](10)
print fns[2](10)

>>> l=[[0]*2]*2
>>> l[0][0]

>>> l[0][0]=1
>>> l

>>> l[0] is l[1]

def add(a, lista):
  l=lista[:]
  if a not in l:
    l+=[a]
  return l

def add(a, lista=None):
  l = [] if lista is None else lista[:]
  if a not in l:
    l+=[a]
  return l


>>> #MODO ERRÓNEO: machacamos la lista con None
>>> l = [3,5,1,2,4]
>>> l_2 = [x*x for x in l.sort()]

>>> #MODO CORRECTO
>>> l = [3,5,1,2,4]
>>> l_2 = [x*x for x in sorted(l)]
>>> l_2