>>> from vagons import Vago
>>> from viatge import seleccio

--ini-enunciat

>>> it1 = list([Vago('AB45', 23, 10), Vago('CB25', 4, 10), Vago('XX22', 4, 0), Vago('XX56', 4, 0), Vago('XY45', 0, 4)])
>>> it2 = seleccio(it1)
>>> next(it2)
'XX22'
>>> next(it2)
'XX56'
>>> next(it2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration

--fi-enunciat
>>> l = []
>>> for i in range(30):
...    l.append(Vago('VA{:02d}'.format(i*2), 4, 0))
...    l.append(Vago('VA{:02d}'.format(i*2+1), i, i))
...
>>> it1 = list(l)
>>> it2 = seleccio(it1)
>>> list(it2)
['VA00', 'VA02', 'VA04', 'VA06', 'VA08', 'VA10', 'VA12', 'VA14', 'VA16', 'VA18', 'VA20', 'VA22', 'VA24', 'VA26', 'VA28', 'VA30', 'VA32', 'VA34', 'VA36', 'VA38', 'VA40', 'VA42', 'VA44', 'VA46', 'VA48', 'VA50', 'VA52', 'VA54', 'VA56', 'VA58']
>>> l = []
>>> for i in range(10):
...    l.append(Vago('VA{:02d}'.format(i*3), 4, 0))
...    l.append(Vago('VA{:02d}'.format(i*3+1), 3, 3))
...    l.append(Vago('VA{:02d}'.format(i*3+2), 5, 5))
...
>>> it1 = list(l)
>>> it2 = seleccio(it1)
>>> list(it2)
['VA00', 'VA03', 'VA06', 'VA09', 'VA12', 'VA15', 'VA18', 'VA21', 'VA24', 'VA27']