المجموعات: العداد والتقصير

from collections import Counter

parole = ["mela", "pera", "mela", "kiwi", "mela", "pera"]
c = Counter(parole)
# Counter({'mela': 3, 'pera': 2, 'kiwi': 1})

c["mela"]            # 3
c["banana"]          # 0   (default for missing keys, NO KeyError)
c.most_common(2)     # [('mela', 3), ('pera', 2)]

Counter("ciao mondo")
# Counter({'o': 2, 'c': 1, 'i': 1, 'a': 1, ' ': 1, 'm': 1, 'n': 1, 'd': 1})

from collections import defaultdict

gruppi = defaultdict(list)        # factory = list (empty list)
for nome in ["Ada", "Linus", "Ada", "Grace"]:
    gruppi[nome].append(1)
# defaultdict(list, {'Ada': [1, 1], 'Linus': [1], 'Grace': [1]})

gruppi = {}
for nome in [...]:
    if nome not in gruppi:
        gruppi[nome] = []
    gruppi[nome].append(1)

from collections import namedtuple

Punto = namedtuple("Punto", ["x", "y"])
p = Punto(3, 4)
p.x          # 3 (access by name)
p[0]         # 3 (access by index, still a tuple)
p.x + p.y    # 7

# typical use: return multiple values from a function
def divisione(a, b):
    Risultato = namedtuple("Risultato", ["quoziente", "resto"])
    return Risultato(a // b, a % b)

r = divisione(17, 5)
r.quoziente   # 3
r.resto       # 2

from collections import namedtuple
Point = namedtuple('Point', ['x', 'y'])
p = Point(10, 20)
print(p.x, p.y)