3.4. Typing Mapping¶

Before Python 3.9 you need from typing import Dict
Since Python 3.9: PEP 585 -- Type Hinting Generics In Standard Collections
Since Python 3.10: PEP 604 -- Allow writing union types as X | Y

3.4.1. Dict¶

Empty:

>>> data: dict = {}
>>> data: dict = dict()

Generic:

>>> data: dict = {'firstname': 'Mark', 'lastname': 'Watney'}

Strict:

>>> data: dict[str, str] = {'firstname': 'Mark', 'lastname': 'Watney'}
>>> data: dict[str, str|int] = {'firstname': 'Mark', 'lastname': 'Watney', 'age': 40}
>>>
>>> data: dict[int, str] = {
...    0: 'setosa',
...    1: 'virginica',
...    2: 'versicolor'}
>>>
>>> data: dict[float, str] = {
...    5.8: 'sepal_length',
...    2.7: 'sepal_width',
...    5.1: 'petal_length',
...    1.9: 'petal_width'}
>>>
>>> data: dict[str, float] = {
...    'sepal_length': 5.8,
...    'sepal_width': 2.7,
...    'petal_length': 5.1,
...    'petal_width': 1.9}

3.4.2. Use Case - 0x01¶

>>> calendarium: dict[int, str] = {
...     1961: 'Yuri Gagarin fly to space',
...     1969: 'Neil Armstrong set foot on the Moon',
... }

3.4.3. Use Case - 0x02¶

>>> calendarium: dict[int, list[str]] = {
...     1961: ['Yuri Gagarin fly to space', 'Alan Shepard fly to space'],
...     1969: ['Neil Armstrong set foot on the Moon'],
... }

3.4.4. Further Reading¶

More information in Type Annotations
More information in CI/CD Type Checking

3.4.5. Assignments¶

Code 3.40. Solution¶

"""
* Assignment: Typing Annotations Mapping
* Complexity: easy
* Lines of code: 3 lines
* Time: 2 min

English:
    1. Declare proper types for variables
    2. Run doctests - all must succeed

Polish:
    1. Zadeklaruj odpowiedni typ zmiennych
    2. Uruchom doctesty - wszystkie muszą się powieść

Tests:
    >>> import sys; sys.tracebacklimit = 0

    >>> assert a == {}, \
    'Do not modify variable `a` value, just add type annotation'
    >>> assert b == {'firstname': 'Mark', 'lastname': 'Watney'}, \
    'Do not modify variable `b` value, just add type annotation'
    >>> assert c == {'firstname': 'Mark', 'lastname': 'Watney', 'age': 40}, \
    'Do not modify variable `c` value, just add type annotation'
"""

# Declare proper types for variables
a: ...
b: ...
c: ...

# Do not modify lines below
a = {}
b = {'firstname': 'Mark', 'lastname': 'Watney'}
c = {'firstname': 'Mark', 'lastname': 'Watney', 'age': 40}