KarChunTCohesion and Coupling
Understand the concepts of cohesion and coupling in Python OOP, and how they affect code maintainability and design.
Important
- High coupling and low cohesion can lead to difficult-to-maintain code
- Low coupling and high cohesion can lead to more maintainable, understandable, and flexible code.
Coupling
Coupling refers to the degree of interdependence between software modules. Meaning that how closely connected modules are, and how much they rely on each other.
- High coupling means modules are tightly (closely) connected and changes in one module can significantly affect others.
- Low coupling means modules are independent and changes in one module has minimal impact on others.
Cohesion
Cohesion refers to the degree to which elements of a module belong together. Meaning that how closely related and focused the responsibilities of a single module are.
- High cohesion means that a module has a single purpose, well-defined responsibility and all its elements are closely related.
- Low cohesion means that a module has multiple purposes, unrelated responsibilties and its elements are not closely related.
Differences of Cohesion and Coupling
| Aspect | Coupling | Cohesion |
|---|---|---|
| Definition | Degree of interdependence between modules | Degree to which elements within a module belong together |
| Purpose | Relationships between modules | Relationships within a module |
| Goal | Low coupling (loosely couple) | High cohesion (highly cohesive) |
Here's a real-life example using a Library System to illustrate low coupling and high cohesion.
High Cohesion - Each module has high cohesion (focused responsibilities):
- The
BookManagermodule only manages books (add, remove, search). Low Coupling: BookManager,UserManager, andNotificationManagerwork independently and interact through clear interfaces.
Low Coupling - The modules are loosely coupled:
- The dashed arrows show low coupling (modules interact but are not tightly bound).