16.4. OOP Attribute Define

• Attribute Annotation is optional, but a good practice

16.4.1. No Attribute Definition

>>> class User:
...     pass

16.4.2. Basic Types

>>> class User:
...     firstname: str
...     lastname: str
...     age: int

16.4.3. Union

>>> class User:
...     firstname: str
...     lastname: str
...     age: int | float

16.4.4. Optional

>>> class User:
...     firstname: str
...     lastname: str
...     age: int | float
...     height: float | None
...     weight: float | None

16.4.5. Sequences

• Since Python 3.9 you can use list[str]

• Before Python 3.9 use list without specifying type of elements inside

>>> class User:
...     firstname: str
...     lastname: str
...     age: int
...     groups: list[str]

16.4.6. Relation One to One

>>> class Group:
...     gid: int
...     name: int
>>>
>>>
>>> class User:
...     firstname: str
...     lastname: str
...     group: Group

16.4.7. Relation One to Many

>>> class Group:
...     gid: int
...     name: str
>>>
>>>
>>> class User:
...     firstname: str
...     lastname: str
...     groups: list[Group]

16.4.8. Example

>>> class User:
...     firstname: str
...     lastname: str
...     email: str
...     active: bool
...     age: int | float
...     height: float | None
...     weight: float | None
...     groups: list[str] | None
...     friends: list['User'] | None

16.4.9. Good Practices

• snake_case name convention

• Attributes should be defined only in __init__() method

• More information in OOP Init Method

16.4.10. Use Case - 0x01

>>> class Point:
...     x: int
...     y: int
...     z: int

16.4.11. Use Case - 0x02

>>> class Date:
...     year: int
...     month: int
...     day: int

16.4.12. Use Case - 0x03

>>> class Laptop:
...     cpu: str
...     ram: str
...     ssd: str

16.4.13. Use Case - 0x04

>>> class Iris:
...     features: list[float]
...     label: str

16.4.14. Use Case - 0x05

>>> class Iris:
...     sepal_length: float
...     sepal_width: float
...     petal_length: float
...     petal_width: float
...     species: str

16.4.15. Use Case - 0x06

>>> from datetime import date
>>> from typing import Literal
>>>
>>>
>>> class Address:
...     type: Literal['home', 'work']
...     street: str
...     house: str
...     apartment: str
...     post_code: str
...     city: str
...     region: str
...     country: str
>>>
>>>
>>> class PhoneNumber:
...     type: Literal['home', 'work', 'mobile']
...     number: str
>>>
>>>
>>> class Person:
...     firstname: str
...     lastname: str
...     age: int | float
...     birthdate: date
...     gender: Literal['male', 'female']
...     height: float | None
...     weight: float | None
...     education: list[str] | None
...     job: str | None
...     addresses: list[Address] | None
...     emails: list[str] | None
...     phones: PhoneNumber | None
...     friends: list['Person'] | None

16.4.16. Assignments

Code 16.5. Solution

"""
* Assignment: OOP Attribute Define
* Type: class assignment
* Complexity: easy
* Lines of code: 6 lines
* Time: 3 min

English:
    1. Modify code below
    2. Add type annotation attibutes to model the data:
       a. Mark, USA, 1969-07-21
       b. Nasa, USA, 1969-07-21
    3. Run doctests - all must succeed

Polish:
    1. Zmodyfikuj kod poniżej
    2. Dodaj anotację typów atrybutów by zamodelować dane:
       a. Mark, USA, 1969-07-21
       b. Nasa, USA, 1969-07-21
    3. Uruchom doctesty - wszystkie muszą się powieść

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

    >>> assert len(Astronaut.__annotations__) == 3
    >>> assert len(SpaceAgency.__annotations__) == 3
"""


# Mark, USA, 1969-07-21
# Nasa, USA, 1969-07-21

class Astronaut:
    ...


class SpaceAgency:
    ...