2.2. Annotation Sequence

2.2.1. Rationale

  • Before Python 3.9 you need from typing import List, Tuple, Set, Frozenset

  • Since Python 3.9: PEP 585 -- Type Hinting Generics In Standard Collections

>>> DATA = [(5.8, 2.7, 5.1, 1.9, 'virginica'),
...         (5.1, 3.5, 1.4, 0.2, 'setosa'),
...         (5.7, 2.8, 4.1, 1.3, 'versicolor')]
>>>
>>> x = DATA[0][-1]
>>> x  
>>> # IDE don't know what type is species
>>> # and cannot give hints for autocompletion

>>> DATA = [(5.8, 2.7, 5.1, 1.9, 'virginica'),
...         (5.1, 3.5, 1.4, 0.2, 'setosa'),
...         (5.7, 2.8, 4.1, 1.3, 'versicolor')]
>>>
>>> x: str = DATA[0][-1]
>>> x  
>>> # IDE knows exactly what type is species
>>> # and what methods hint for autocompletion

2.2.2. Tuple

>>> data: tuple = ()
>>> data: tuple = tuple()
>>> data: tuple = 'a', 2, 3.3
>>> data: tuple = ('a', 2, 3.3)

>>> data: tuple[int, int, int] = (1, 2, 3)
>>> data: tuple[str, str, str] = ('setosa', 'virginica', 'versicolor')
>>> data: tuple[str, int, float] = ('a', 2, 3.3)
>>> data: tuple[int, ...] = (1, 2, 3)
>>> data: tuple[str, ...] = ('setosa', 'virginica', 'versicolor')

2.2.3. List

>>> data: list = list()
>>> data: list = []
>>> data: list = ['a', 1, 2.2]

>>> data: list[int] = [1, 2, 3, 4]
>>> data: list[float] = [5.8, 2.7, 5.1, 1.9]
>>> data: list[str] = ['a', 'b', 'c', 'd']

2.2.4. Set

>>> data: set = set()
>>> data: set = {'a', 1, 2.2}

>>> data: set[int] = {1, 2, 3}
>>> data: set[float] = {0.0, 1.1, 2.2}
>>> data: set[str] = {'a', 'b', 'c'}

2.2.5. Frozenset

>>> data: frozenset = frozenset()
>>> data: frozenset = frozenset({'a', 1, 2.2})

>>> data: frozenset[int] = frozenset({1, 2, 3})
>>> data: frozenset[float] = frozenset({0.0, 1.1, 2.2})
>>> data: frozenset[str] = frozenset({'a', 'b', 'c'})

2.2.6. List of Tuples

>>> data: list[tuple] = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica')]

>>> data: list[tuple[float, float, float, float, str]] = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica')]

>>> row = tuple[float, float, float, float, str]
>>> data: list[row] = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica')]

2.2.7. List of Lists

>>> data: list[list] = [
...     [1, 2, 3],
...     [4, 5, 6],
...     [7, 8, 9],
... ]

>>> data: list[list[int]] = [
...     [1, 2, 3],
...     [4, 5, 6],
...     [7, 8, 9],
... ]

2.2.8. Aliases

>>> GeographicCoordinate = tuple[float, float]
>>> locations: list[GeographicCoordinate] = [
...     (25.91375, -60.15503),
...     (-11.01983, -166.48477),
...     (-11.01983, -166.48477)
... ]

>>> Iris = tuple[float, float, float, float, str]
>>> data: list[Iris] = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica'),
... ]

2.2.9. Unions

from typing import Union


data: list[Union[list, tuple, set]] = [
    [1, 2, 3],
    (4, 5, 6),
    {7, 8, 9},
]

data: list[Union[list[int], tuple[int, ...], set[int]]] = [
    [1, 2, 3],
    (4, 5, 6),
    {7, 8, 9},
]

row = Union[list[int], tuple[int, ...], set[int]]
data: list[row] = [
    [1, 2, 3],
    (4, 5, 6),
    {7, 8, 9},
]

2.2.10. NamedTuple

from typing import NamedTuple


class Astronaut(NamedTuple):
    firstname: str
    lastname: str
    agency: str = 'NASA'


astro: Astronaut = Astronaut('Mark', lastname='Watney')

print(astro)
# Astronaut(firstname='Mark', lastname='Watney', agency='NASA')

2.2.11. Before Python 3.9

Tuple:

from typing import Tuple

data: tuple = ()
data: tuple = tuple()
data: tuple = 'a', 2, 3.3
data: tuple = ('a', 2, 3.3)

data: Tuple[int, int, int] = (1, 2, 3)
data: Tuple[str, str, str] = ('setosa', 'virginica', 'versicolor')
data: Tuple[str, int, float] = ('a', 2, 3.3)
data: Tuple[int, ...] = (1, 2, 3)
data: Tuple[str, ...] = ('setosa', 'virginica', 'versicolor')

List:

from typing import List

data: list = list()
data: list = []
data: list = ['a', 1, 2.2]

data: List[int] = [1, 2, 3, 4]
data: List[float] = [5.8, 2.7, 5.1, 1.9]
data: List[str] = ['a', 'b', 'c', 'd']

Set:

from typing import Set

data: set = set()
data: set = {'a', 1, 2.2}

data: Set[int] = {1, 2, 3}
data: Set[float] = {0.0, 1.1, 2.2}
data: Set[str] = {'a', 'b', 'c'}

Frozenset:

from typing import FrozenSet

data: frozenset = frozenset()
data: frozenset = frozenset({'a', 1, 2.2})

data: FrozenSet[int] = frozenset({1, 2, 3})
data: FrozenSet[float] = frozenset({0.0, 1.1, 2.2})
data: FrozenSet[str] = frozenset({'a', 'b', 'c'})

List[Tuple]:

from typing import List, Tuple

data: List[tuple] = [
    (4.7, 3.2, 1.3, 0.2, 'setosa'),
    (7.0, 3.2, 4.7, 1.4, 'versicolor'),
    (7.6, 3.0, 6.6, 2.1, 'virginica'),
]

data: List[Tuple[float, float, float, float, str]] = [
    (4.7, 3.2, 1.3, 0.2, 'setosa'),
    (7.0, 3.2, 4.7, 1.4, 'versicolor'),
    (7.6, 3.0, 6.6, 2.1, 'virginica'),
]

Row = Tuple[float, float, float, float, str]
data: List[Row] = [
    (4.7, 3.2, 1.3, 0.2, 'setosa'),
    (7.0, 3.2, 4.7, 1.4, 'versicolor'),
    (7.6, 3.0, 6.6, 2.1, 'virginica'),
]

List[List]:

from typing import List

data: List[list] = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9],
]

data: List[List[int]] = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9],
]

Aliases:

from typing import List, Tuple


GeographicCoordinate = Tuple[float, float]
locations: List[GeographicCoordinate] = [
    (25.91375, -60.15503),
    (-11.01983, -166.48477),
    (-11.01983, -166.48477)
]

Iris = Tuple[float, float, float, float, str]
data: List[Iris] = [
    (4.7, 3.2, 1.3, 0.2, 'setosa'),
    (7.0, 3.2, 4.7, 1.4, 'versicolor'),
    (7.6, 3.0, 6.6, 2.1, 'virginica'),
]

Union:

from typing import Union, List, Tuple, Set


data: List[Union[list, tuple, set]] = [
    [1, 2, 3],
    (4, 5, 6),
    {7, 8, 9},
]


data: List[Union[List[int], Tuple[int, int, int], Set[int]]] = [
    [1, 2, 3],
    (4, 5, 6),
    {7, 8, 9},
]


Row = Union[List[int],
            Tuple[int, int, int],
            Set[int]]

data: List[Row] = [
    [1, 2, 3],
    (4, 5, 6),
    {7, 8, 9},
]

2.2.12. Further Reading