11.1. OOP Enum¶
List of finite choices
Enumerations
EnumIntEnumFlagIntFlag
11.1.1. Syntax¶
>>> from enum import Enum
>>>
>>>
>>> class Select(Enum):
... OPTION1 = 1
... OPTION2 = 2
11.1.2. Example¶
>>> from enum import Enum
>>>
>>>
>>> class Color(Enum):
... RED = '#FF0000'
... GREEN = '#00FF00'
... BLUE = '#0000FF'
>>> from enum import Enum
>>>
>>>
>>> class HTTPStatus(Enum):
... OK = 200
... CREATED = 201
... BAD_REQUEST = 400
... NOT_FOUND = 404
... INTERNAL_ERROR = 500
11.1.3. Switch¶
>>> from enum import Enum
>>>
>>>
>>> class Color(Enum):
... RED = '#FF0000'
... GREEN = '#00FF00'
... BLUE = '#0000FF'
>>>
>>>
>>> mycolor = Color('#00FF00')
>>>
>>> mycolor
<Color.GREEN: '#00FF00'>
>>>
>>> mycolor.name
'GREEN'
>>>
>>> mycolor.value
'#00FF00'
11.1.4. Identity Check¶
>>> from enum import Enum
>>>
>>>
>>> class Color(Enum):
... RED = '#FF0000'
... GREEN = '#00FF00'
... BLUE = '#0000FF'
>>>
>>>
>>> mycolor = Color('#00FF00')
>>>
>>> mycolor is Color.RED
False
>>> mycolor is Color.GREEN
True
11.1.5. Iterating¶
Iterating over Enum:
>>> from enum import Enum
>>>
>>>
>>> class Color(Enum):
... RED = '#FF0000'
... GREEN = '#00FF00'
... BLUE = '#0000FF'
>>>
>>>
>>> for color in Color:
... print(color)
Color.RED
Color.GREEN
Color.BLUE
11.1.6. Pattern Matching¶
Since Python 3.10: PEP 636 -- Structural Pattern Matching: Tutorial
Note, keycodes can vary depending on operating system and programming language used [mskeycodes], [jskeycodes].
>>> int('0x1B', base=16)
27
>>>
>>> hex(27)
'0x1b'
>>> from enum import Enum
>>>
>>>
>>> class Key(Enum):
... ESC = 27 # 0x1B
... ARROW_LEFT = 37 # 0x25
... ARROW_UP = 38 # 0x26
... ARROW_RIGHT = 39 # 0x27
... ARROW_DOWN = 40 # 0x28
>>>
>>>
>>>
... match keyboard.on_key_press():
... case Key.ESC: game.quit()
... case Key.ARROW_LEFT: game.move_left()
... case Key.ARROW_UP: game.move_up()
... case Key.ARROW_RIGHT: game.move_right()
... case Key.ARROW_DOWN: game.move_down()
... case _: raise ValueError(f'Unrecognized key')
11.1.7. Built-in Enum¶
>>> from http import HTTPStatus
>>>
>>>
>>> HTTPStatus(200).name
'OK'
>>>
>>> HTTPStatus(404).name
'NOT_FOUND'
>>>
>>> HTTPStatus(500).name
'INTERNAL_SERVER_ERROR'
>>>
>>> HTTPStatus(418).name
'IM_A_TEAPOT'
11.1.8. Use Case - 0x01¶
Dead or Alive
>>> from enum import Enum
>>>
>>>
>>> class Status(Enum):
... ALIVE = 'alive'
... DEAD = 'dead'
11.1.9. Use Case - 0x02¶
>>> from enum import Enum
>>>
>>>
>>> class Status(Enum):
... FULL_HEALTH = 100
... DEAD = 0
>>>
>>>
>>> hit_points = 100
>>> Status(hit_points)
<Status.FULL_HEALTH: 100>
>>>
>>>
>>> hit_points = 0
>>> Status(hit_points)
<Status.DEAD: 0>
11.1.10. Use Case - 0x03¶
Issue Status
>>> from enum import Enum
>>>
>>>
>>> class IssueStatus(Enum):
... TODO = 'todo'
... IN_PROGRESS = 'in-progress'
... IN_REVIEW = 'in-review'
... IN_TEST = 'in-test'
... DONE = 'done'
... REJECTED = 'rejected'
11.1.11. Use Case - 0x04¶
HTML Colors
>>> class Color(Enum):
... AQUA = '#00FFFF'
... BLACK = '#000000'
... BLUE = '#0000ff'
... FUCHSIA = '#FF00FF'
... GRAY = '#808080'
... GREEN = '#008000'
... LIME = '#00ff00'
... MAROON = '#800000'
... NAVY = '#000080'
... OLIVE = '#808000'
... PINK = '#ff1a8c'
... PURPLE = '#800080'
... RED = '#ff0000'
... SILVER = '#C0C0C0'
... TEAL = '#008080'
... WHITE = '#ffffff'
... YELLOW = '#FFFF00'
11.1.12. Use Case - 0x05¶
>>> from enum import Enum
>>>
>>>
>>> class Color(Enum):
... RED = '#FF0000'
... GREEN = '#00FF00'
... BLUE = '#0000FF'
>>>
>>>
>>> Point = tuple[int,int]
>>>
>>> def draw_line(A: Point, B: Point, color: Color):
... if type(color) is not Color:
... possible = [str(c) for c in Color]
... raise TypeError(f'Invalid color, possible choices: {possible}')
... print(f'Drawing line from {A} to {B} with color {color.value}')
>>>
>>>
>>> draw_line(A=(0,0), B=(3,5), color=Color.RED)
Drawing line from (0, 0) to (3, 5) with color #FF0000
>>>
>>> draw_line(A=(0,0), B=(3,5), color='red')
Traceback (most recent call last):
TypeError: Invalid color, possible choices: ['Color.RED', 'Color.GREEN', 'Color.BLUE']
11.1.13. Use Case - 0x06¶
r- readw- writex- executerwx- read, write, execute; 0b111 == 0o7rw-- read, write; 0b110 == 0o6r-x- read, execute; 0b101 == 0o5r--- read only; 0b100 == 0o4rwxr-xr--- user=(read,write,execute); group=(read,execute); others=(read)
>>> from enum import Enum
>>> from pathlib import Path
>>>
>>>
>>> class Permission(Enum):
... READ_WRITE_EXECUTE = 0b111
... READ_WRITE = 0b110
... READ_EXECUTE = 0b101
... READ = 0b100
... WRITE_EXECUTE = 0b011
... WRITE = 0b010
... EXECUTE = 0b001
... NONE = 0b000
>>>
>>>
>>> file = Path('/tmp/myfile.txt')
>>> file.touch()
>>> file.stat()
os.stat_result(st_mode=33188, st_ino=98480473, st_dev=16777220,
st_nlink=1, st_uid=501, st_gid=20, st_size=0,
st_atime=1624458230, st_mtime=1624458230,
st_ctime=1624458230)
>>>
>>> permissions = file.stat().st_mode
>>> decimal = int(permissions)
>>> octal = oct(permissions)
>>> binary = bin(permissions)
>>> print(f'{decimal=}, {octal=}, {binary}')
decimal=33188, octal='0o100644', 0b1000000110100100
>>>
>>> *_, user, group, others = oct(permissions)
>>> print(f'{user=} {group=} {others=}')
user='6' group='4' others='4'
>>>
>>> Permission(int(user))
<Permission.READ_WRITE: 6>
>>>
>>> Permission(int(group))
<Permission.READ: 4>
>>>
>>> Permission(int(others))
<Permission.READ: 4>
>>>
>>> file.unlink()
11.1.14. Use Case - 0x07¶
>>> from enum import IntEnum
>>>
>>>
>>> class IndexDrives(IntEnum):
... ControlWord = 0x6040
... StatusWord = 0x6041
... OperationMode = 0x6060
11.1.15. Use Case - 0x08¶
>>> from dataclasses import dataclass
>>> from enum import Enum
>>>
>>>
>>> class Agency(Enum):
... NASA = 1
... ESA = 2
... JAXA = 3
>>>
>>>
>>> @dataclass
... class Astronaut:
... firstname: str
... lastname: str
... agency: Agency
>>>
>>>
>>> mark = Astronaut('Mark', 'Watney', agency='not-existing')
>>> mark = Astronaut('Mark', 'Watney', agency=Agency.NASA)