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

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

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

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

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

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

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

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

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

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

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.