26. Enumerations (Enums):

This Python code snippets that demonstrate the usage of Enumerations (Enums) using Python's enum module to define symbolic names for unique constant values.

1. Basic Enum Example

Copy

from enum import Enum

class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3

print(Color.RED)  # Color.RED
print(Color.RED.value)  # 1
print(Color.RED.name)  # RED

---

2. Iterating Over Enums

Copy

from enum import Enum

class Day(Enum):
    MONDAY = 1
    TUESDAY = 2
    WEDNESDAY = 3

for day in Day:
    print(day.name, day.value)
# Output:
# MONDAY 1
# TUESDAY 2
# WEDNESDAY 3

---

3. Comparison of Enums

Copy

from enum import Enum

class Status(Enum):
    ACTIVE = 1
    INACTIVE = 2

print(Status.ACTIVE == Status.ACTIVE)  # True
print(Status.ACTIVE == Status.INACTIVE)  # False

---

4. Accessing Enum Members Dynamically

Copy

from enum import Enum

class Month(Enum):
    JANUARY = 1
    FEBRUARY = 2
    MARCH = 3

print(Month(1))  # Month.JANUARY
print(Month["FEBRUARY"])  # Month.FEBRUARY

---

5. Enums with Non-Integer Values

Copy

from enum import Enum

class Direction(Enum):
    NORTH = "North"
    EAST = "East"
    SOUTH = "South"
    WEST = "West"

print(Direction.NORTH.value)  # North
print(Direction.WEST)  # Direction.WEST

---

6. Unique Enums Using @unique

Copy

from enum import Enum, unique

@unique
class Fruit(Enum):
    APPLE = 1
    ORANGE = 2
    BANANA = 3

# Uncommenting the following line will raise an error because of duplicate values:
# @unique
# class InvalidFruit(Enum):
#     APPLE = 1
#     PEAR = 1

---

7. Auto Assigning Values to Enums

Copy

from enum import Enum, auto

class TaskStatus(Enum):
    TODO = auto()
    IN_PROGRESS = auto()
    DONE = auto()

print(list(TaskStatus))
# [<TaskStatus.TODO: 1>, <TaskStatus.IN_PROGRESS: 2>, <TaskStatus.DONE: 3>]

---

8. Enum with Methods

Copy

from enum import Enum

class Signal(Enum):
    RED = 1
    YELLOW = 2
    GREEN = 3

    def describe(self):
        return f"{self.name} signal means {self.value}."

print(Signal.RED.describe())  # RED signal means 1.

---

9. Extending Enums with Additional Attributes

Copy

from enum import Enum

class Planet(Enum):
    MERCURY = (3.3e23, 2.4e6)
    VENUS = (4.9e24, 6.1e6)
    EARTH = (6.0e24, 6.4e6)

    def __init__(self, mass, radius):
        self.mass = mass
        self.radius = radius

    def density(self):
        return self.mass / (4/3 * 3.14159 * self.radius**3)

print(Planet.EARTH.density())  # Earth's density

---

10. Flag Enum for Bitwise Operations

Copy

from enum import Flag, auto

class Permissions(Flag):
    READ = auto()
    WRITE = auto()
    EXECUTE = auto()

user_perms = Permissions.READ | Permissions.WRITE
print(user_perms)  # Permissions.READ|WRITE
print(Permissions.WRITE in user_perms)  # True
print(user_perms & Permissions.EXECUTE)  # Permissions.0 (no EXECUTE permission)

---

These examples highlight the power and versatility of Python's enum module, which makes code more readable, organized, and maintainable by providing symbolic names for constant values.