>>> from concurs import canvi

>>> noms = ['Pau', 'Anna', 'Pol', 'Joan', 'Maria']
>>> canvi (noms, 'Pol', 'Maria')
>>> noms
['Pau', 'Anna', 'Maria', 'Joan', 'Pol']
>>> noms = ['Pau', 'Anna', 'Pol', 'Joan', 'Maria']
>>> canvi (noms, 'Pol', 'Roser')
>>> noms
['Pau', 'Anna', 'Pol', 'Joan', 'Maria']

>>> noms = ['Pau', 'Anna', 'Pol', 'Joan', 'Maria']
>>> canvi (noms, 'Pol', 'Pau')
>>> noms
['Pol', 'Anna', 'Pau', 'Joan', 'Maria']

>>> noms = ['Pau', 'Anna', 'Pol', 'Joan', 'Maria']
>>> canvi (noms, 'Pol', 'Pau')
>>> noms
['Pol', 'Anna', 'Pau', 'Joan', 'Maria']

>>> noms = ['Pau', 'Anna', 'Pol', 'Joan', 'Maria']
>>> canvi (noms, 'Pol', 'Pol')
>>> noms
['Pau', 'Anna', 'Pol', 'Joan', 'Maria']

>>> noms = ['Pau', 'Anna', 'Pol', 'Joan', 'Maria']
>>> canvi (noms, 'Anna', 'Pau')
>>> noms
['Anna', 'Pau', 'Pol', 'Joan', 'Maria']