Enforces the singleton design pattern by wrapping a class constructor to return the same instance on every instantiation.

Expresses the intent to use a singleton pattern via a decorator in Python code.

When a single shared instance of a class is needed throughout the program, such as for a logger, configuration manager, or database connection.

Used in Python code where a global singleton is desired, e.g., logging, configuration, caching, or resource management.

@singleton class <ClassName>: pass

@singleton class <ClassName>: pass

<ClassName>

• Logger
• config
• database
• cache
• manager

• @singleton from third‑party libraries
• metaclass‑based Singleton
• module‑level instance

Forgetting to make __init__ idempotent, not handling inheritance correctly, lacking thread safety, inadvertently creating multiple instances via subclassing.

@dataclass, @property, @lru_cache, @staticmethod

• singleton pattern
• decorator pattern
• singleton idiom

Ensures exactly one instance per interpreter; thread‑safety depends on the decorator implementation; subclassing may break the singleton guarantee unless carefully designed.

Provides a global point of access to a single shared object, often used for managing shared resources like loggers or configuration.

@singleton decorator

Thread‑safe singleton implementation using a metaclass or module‑level instance