Practical Inheritance Design
Inheritance Design Principles
Effective inheritance design requires careful consideration of class relationships, responsibilities, and potential future extensions. This section explores practical strategies for creating robust and maintainable class hierarchies.
Composition vs Inheritance
| Approach |
Pros |
Cons |
| Inheritance |
Code reuse |
Tight coupling |
| Composition |
Flexible |
More verbose |
| Delegation |
Loose coupling |
Additional complexity |
Designing Flexible Class Hierarchies
class StorageSystem:
def __init__(self, capacity):
self.capacity = capacity
self._used_space = 0
def add_data(self, size):
if self._used_space + size <= self.capacity:
self._used_space += size
return True
return False
class CloudStorage(StorageSystem):
def __init__(self, capacity, provider):
super().__init__(capacity)
self.provider = provider
def backup_data(self):
## Implementation of cloud backup
pass
class LocalStorage(StorageSystem):
def __init__(self, capacity, device_type):
super().__init__(capacity)
self.device_type = device_type
def optimize_storage(self):
## Storage optimization logic
pass
Inheritance Design Workflow
graph TD
A[Base Class Design] --> B[Define Core Attributes]
B --> C[Define Common Methods]
C --> D[Create Specialized Subclasses]
D --> E[Implement Specific Behaviors]
Abstract Base Class Pattern
from abc import ABC, abstractmethod
class DataProcessor(ABC):
@abstractmethod
def process(self, data):
pass
def validate_data(self, data):
## Common validation logic
return data is not None
class JSONProcessor(DataProcessor):
def process(self, data):
## JSON-specific processing
pass
class XMLProcessor(DataProcessor):
def process(self, data):
## XML-specific processing
pass
Dependency Injection Technique
class Logger:
def log(self, message):
print(f"Log: {message}")
class DatabaseConnection:
def __init__(self, logger):
self.logger = logger
def connect(self):
try:
## Connection logic
self.logger.log("Database connected successfully")
except Exception as e:
self.logger.log(f"Connection error: {e}")
Inheritance Anti-Patterns
- Deep inheritance hierarchies
- God classes
- Tight coupling
- Violation of Liskov Substitution Principle
Design Recommendations
- Keep inheritance hierarchies shallow
- Favor composition over inheritance
- Use interfaces and abstract base classes
- Follow SOLID principles
- Design for extension, not modification
Complex Inheritance Example
class Payment:
def __init__(self, amount):
self.amount = amount
class CreditCardPayment(Payment):
def __init__(self, amount, card_number):
super().__init__(amount)
self.card_number = card_number
def validate(self):
## Credit card validation logic
pass
class PayPalPayment(Payment):
def __init__(self, amount, email):
super().__init__(amount)
self.email = email
def authenticate(self):
## PayPal authentication
pass
- Minimize method resolution overhead
- Use
__slots__ for memory optimization
- Profile and benchmark inheritance implementations
At LabEx, we emphasize that good inheritance design is about creating flexible, maintainable, and extensible code structures that solve real-world problems efficiently.
