Instance Attributes or Class Attributes: Which is Better for Python\'s Singleton Classes?

Per-Instance Attributes vs. Class Attributes for Single-Instance Classes

In Python programming, when creating classes with only a single instance, it's common to consider whether to use instance attributes or class attributes to manage the data.

Instance Attributes

Instance attributes are specific to each instance of a class and are created when the instance is instantiated. This approach ensures that each instance has its own unique set of attributes.

Class Attributes

Class attributes, on the other hand, are shared among all instances of a class and are available as part of the class definition before any instances are created. Class attributes provide a convenient way to define constants or shared values that remain the same for all instances.

Which to Use for Single-Instance Classes?

When dealing with single-instance classes, the choice between instance attributes and class attributes is less critical. However, performance considerations and coding conventions should be taken into account.

Performance Considerations

Class attributes are marginally faster to access because they do not require an extra level of lookup to access the instance's attributes. Performance differences are negligible in most cases, but if optimization is crucial, using class attributes can be beneficial.

Coding Conventions and Idioms

Python's coding conventions favor instance attributes for data that varies between instances. Class attributes are typically used for constants or shared data that should not change at runtime.

Therefore, if there will only be one instance of a class and the attributes are expected to remain constant across instances, using instance attributes is preferred. This approach aligns with Python's coding conventions and provides a slight performance advantage over class attributes.

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