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¶
Example: https://github.com/pandas-dev/pandas/blob/master/pandas/core/frame.py#L458
More information in Type Annotations
More information in CI/CD Type Checking