Concept Entry - Python: Enum

content/python/concepts/enum/enum.md

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+---
+Title: '`enum`'
+Description: 'Represents a set of unique, immutable constants in Python.'
+Subjects:
+  - 'Code Foundations'
+  - 'Computer Science'
+Tags:
+  - 'Data Types'
+  - 'Enum'
+  - 'Python'
+  - 'Variables'
+CatalogContent:
+  - 'learn-python-3'
+  - 'paths/computer-science'
+---
+
+**`Enum`** (short for _enumeration_) is a data type in Python used to define a set of named, immutable constants.
+
+Enumerations make code more readable and maintainable by replacing **magic numbers** or strings with meaningful names.
+
+Enums are part of Python's built in `enum` module, introduced in Python 3.4.
+
+> **Note:** Magic numbers are unclear, hardcoded values in code. For example, `80` in a speed-checking program might be confusing. Replacing it with an enum constant, like `SpeedLimit.HIGHWAY`, makes the code easier to read and maintain.
+
+## Syntax
+
+```python
+from enum import Enum
+
+class EnumName(Enum):
+  MEMBER1 = value1
+  MEMBER2 = value2
+```
+
+- `EnumName`: The name of the enum class.
+- `MEMBER1`, `MEMBER2`: Names of the constants.
+- `value1`, `value2`: Values assigned to the constants (e.g. numbers or strings).
+
+## `enum` Module
+
+The `enum` module provides the `Enum` class for creating enums. It also includes:
+
+- `IntEnum`: Ensures values are integers.
+- `Flag`: Allows combining constants with bitwise operations.
+- `Auto`: Automatically assigns values.
+
+Enums provide methods like `.name` (the constant name) and `.value` (the assigned value).
+
+## Example
+
+This example shows how to create an enum for days of the week:
+
+```python
+from enum import Enum
+
+class Weekday(Enum):
+  MONDAY = 1
+  TUESDAY = 2
+  WEDNESDAY = 3
+
+# Accessing members
+print(Weekday.MONDAY)
+print(Weekday.MONDAY.name)
+print(Weekday.MONDAY.value)
+
+# Iterating through members
+for day in Weekday:
+  print(day)
+```
+
+This would output with the following:
+
+```shell
+Weekday.MONDAY
+MONDAY
+1
+Weekday.MONDAY
+Weekday.TUESDAY
+Weekday.WEDNESDAY
+```
+
+## Codebyte
+
+Here is how enums can represent traffic light states:
+
+```codebyte/python
+from enum import Enum
+
+class TrafficLight(Enum):
+  RED = 'Stop'
+  YELLOW = 'Caution'
+  GREEN = 'Go'
+
+def traffic_action(light):
+  if light == TrafficLight.RED:
+    return "Stop your car."
+  elif light == TrafficLight.YELLOW:
+    return "Prepare to stop."
+  elif light == TrafficLight.GREEN:
+    return "You can go."
+
+# Example usage
+current_light = TrafficLight.RED
+print(traffic_action(current_light))
+```