*Memo:
A frozenset can be iterated with a for statement as shown below:
<1D frozenset>:
for x in frozenset([10, 20, 30, 40, 50]):
print(x)
# 40
# 10
# 50
# 20
# 30
<2D frozenset>:
for x in frozenset([frozenset([10, 20, 30, 40]),
frozenset([50, 60, 70, 80])]):
for y in x:
print(y)
# 40
# 10
# 20
# 30
# 80
# 50
# 60
# 70
<3D frozenset>:
for x in frozenset([frozenset([frozenset([10, 20]),
frozenset([30, 40])]),
frozenset([frozenset([50, 60]),
frozenset([70, 80])])]):
for y in x:
for z in y:
print(z)
# 40
# 30
# 10
# 20
# 80
# 70
# 50
# 60
A frozenset can be unpacked with an assignment and for statement, function and * but not with ** as shown below:
v1, v2, v3 = frozenset([0, 1, 2])
print(v1, v2, v3)
# 0 1 2
v1, *v2, v3 = frozenset([0, 1, 2, 3, 4, 5])
print(v1, v2, v3) # 0 [1, 2, 3, 4] 5
print(v1, *v2, v3) # 0 1 2 3 4 5
for v1, v2, v3 in frozenset([frozenset([0, 1, 2]), frozenset([3, 4, 5])]):
print(v1, v2, v3)
# 3 4 5
# 0 1 2
for v1, *v2, v3 in frozenset([frozenset([0, 1, 2, 3, 4, 5]),
frozenset([6, 7, 8, 9, 10, 11])]):
print(v1, v2, v3)
print(v1, *v2, v3)
# 6 [7, 8, 9, 10] 11
# 6 7 8 9 10 11
# 0 [1, 2, 3, 4] 5
# 0 1 2 3 4 5
print(*frozenset([0, 1]), 2, *frozenset([3, 4, *frozenset([5])]))
# 0 1 2 3 4 5
print(frozenset([*frozenset([0, 1]), 2,
*frozenset([3, 4, *frozenset([5])])]))
# frozenset({0, 1, 2, 3, 4, 5})
def func(p1='a', p2='b', p3='c', p4='d', p5='e', p6='f'):
print(p1, p2, p3, p4, p5, p6)
func()
# a b c d e f
func(*frozenset([0, 1, 2, 3]), *frozenset([4, 5]))
# 0 1 2 3 4 5
def func(p1='a', p2='b', *args):
print(p1, p2, args)
print(p1, p2, *args)
print(p1, p2, ['A', 'B', *args, 'C', 'D'])
func()
# a b ()
# a b Nothing
# a b ['A', 'B', 'C', 'D']
func(*frozenset([0, 1, 2, 3]), *frozenset([4, 5]))
# 0 1 (2, 3, 4, 5)
# 0 1 2 3 4 5
# 0 1 ['A', 'B', 2, 3, 4, 5, 'C', 'D']
frozenset() can create a frozenset with or without an iterable as shown below:
*Memo:
- The 1st argument is
iterable(Optional-Default:()-Type:Iterable):- Don't use
iterable=.
- Don't use
# Empty frozenset
print(frozenset())
print(frozenset(()))
# frozenset()
print(frozenset([0, 1, 2, 3, 4])) # list
print(frozenset((0, 1, 2, 3, 4))) # tuple
print(frozenset(iter([0, 1, 2, 3, 4]))) # iterator
print(frozenset({0, 1, 2, 3, 4})) # set
print(frozenset(frozenset([0, 1, 2, 3, 4]))) # frozenset
print(frozenset(range(5))) # range
# frozenset({0, 1, 2, 3, 4})
print(frozenset({'name': 'John', 'age': 36})) # dict
print(frozenset({'name': 'John', 'age': 36}.keys())) # dict.keys()
# frozenset({'age', 'name'})
print(frozenset({'name': 'John', 'age': 36}.values())) # dict.values()
# frozenset({'John', 36})
print(frozenset({'name': 'John', 'age': 36}.items())) # dict.items()
# frozenset({('name', 'John'), ('age', 36)})
print(frozenset('Hello')) # str
# frozenset({'o', 'l', 'e', 'H'})
print(frozenset(b'Hello')) # bytes
print(frozenset(bytearray(b'Hello'))) # bytearray
# frozenset({72, 108, 101, 111})
A frozenset comprehension can create a frozenset as shown below:
<1D frozenset>:
sample = frozenset([0, 1, 2, 3, 4, 5, 6, 7])
A = frozenset(x**2 for x in sample)
print(A)
# frozenset({0, 1, 4, 36, 9, 16, 49, 25})
<2D frozenset>:
sample = frozenset([frozenset([0, 1, 2, 3]), frozenset([4, 5, 6, 7])])
A = frozenset(frozenset(y**2 for y in x) for x in sample)
print(A)
# frozenset({frozenset({16, 25, 36, 49}), frozenset({0, 1, 4, 9})})
<3D frozenset>:
sample = frozenset([frozenset([frozenset([0, 1]), frozenset([2, 3])]),
frozenset([frozenset([4, 5]), frozenset([6, 7])])])
A = frozenset(frozenset(frozenset(z**2 for z in y) for y in x) for x in sample)
print(A)
# frozenset({frozenset({frozenset({16, 25}), frozenset({49, 36})}),
# frozenset({frozenset({9, 4}), frozenset({0, 1})})})
Be careful, a big frozenset gets MemoryError as shown below:
A = range(1000000000)
print(frozenset(A))
# MemoryError
A = frozenset([x for x in range(1000000000)])
# MemoryError