3.4. Sequence Frozenset¶

3.4.1. Rationale¶

Only unique values

Immutable - cannot add, modify or remove items

Can store elements of any hashable types

Has all set methods such as .intersect(), .subset() .union(), etc.

One solid block in memory

3.4.2. Type Definition¶

Set is ordered data structure

Do not support getitem

Do not support slice

Defining only with frozenset() - no short syntax

Comma after last element is optional

Brackets are required

Listing 3.9. set type definition¶

data = frozenset()

data = frozenset({1})
data = frozenset({1, 2, 3})
data = frozenset({1.1, 2.2, 3.3})
data = frozenset({True, False})
data = frozenset({'a', 'b', 'c'})
data = frozenset({'a', 1, 2.2, True, None})

3.4.3. Type Casting¶

frozenset() converts argument to frozenset

data = [1, 2, 3]
frozenset(data)
# frozenset({1, 2, 3})

data = (1, 2, 3)
frozenset(data)
# frozenset({1, 2, 3})

data = {1, 2, 3}
frozenset(data)
# frozenset({1, 2, 3})

data = frozenset({1, 2, 3})
frozenset(data)
# frozenset({1, 2, 3})

data = [1, 2, 3, [4, 5]]
frozenset(data)
# TypeError: unhashable type: 'list'

data = [1, 2, 3, (4, 5)]
frozenset(data)
# frozenset({(4, 5), 1, 2, 3})

3.4.4. Frozenset or Set¶

Both:

unique elements

only hashable elements

Frozenset:

ordered

immutable

one contingent block of data in memory

Set:

unordered

mutable

implemented in memory as list of pointers to objects

objects are scattered in memory

3.4.5. Assignments¶

3.4.5.1. Sequence Frozenset Newline¶

Complexity level: easy
Lines of code to write: 2 lines
Estimated time of completion: 5 min
Solution: solution/sequence_frozenset_newline.py

English

Use data from "Input" section (see below)
Define result: str
Use str.join() to join lines of text with newline (\n) character
Compare result with "Output" section (see below)

Polish

Użyj danych z sekcji "Input" (patrz poniżej)
Zdefiniuj result: str
Użyj str.join() aby połączyć linie tekstu znakiem końca linii (\n)
Porównaj wyniki z sekcją "Output" (patrz poniżej)

Innput

DATA = frozenset({
    'We choose to go to the Moon.',
    'We choose to go to the Moon in this decade and do the other things.',
    'Not because they are easy, but because they are hard.'})

Output

result: str
# 'We choose to go to the Moon.\nWe choose to go to the Moon in this decade and do the other things.\nNot because they are easy, but because they are hard.'