import sys class RegularPoint: pass class SlottedPoint: __slots__ = ('x', 'y')
class Employee: def __init__(self, name): self._name = name @property def name(self): return self._name @name.setter def name(self, value): if not value: raise ValueError("Name cannot be empty") self._name = value Use code with caution. 5. Polymorphism and Duck Typing in Action
You can dynamically create a class using the type function: python 3 deep dive part 4 oop high quality
By default, Python instances store attributes in a dynamic dictionary ( __dict__ ), which provides flexibility at the cost of memory overhead. When you define __slots__ in a class, you tell Python to allocate a fixed amount of memory for a predetermined set of instance attributes, preventing the creation of __dict__ and __weakref__ for each instance.
Writing explicit getX() and setX() methods is an anti-pattern in Python. Use the @property decorator to turn methods into attributes. This keeps your API clean while allowing you to validate data or compute values dynamically. When you define __slots__ in a class, you
class Secret: def __init__(self): self.public = "Everyone sees this" self._protected = "Please don't touch" self.__private = "Name mangled"
Every object in Python has a type, and that type is defined by a class. You can inspect an object's class using the __class__ attribute or the built-in type() function. This keeps your API clean while allowing you
Define a plugin system where third-party code must implement certain methods. Register virtual subclasses with @Drawable.register .
class OptimizedPoint: __slots__ = ('x', 'y') def __init__(self, x: float, y: float): self.x = x self.y = y Use code with caution. Trade-offs of __slots__
If you do not design class initializers with keyword arguments ( **kwargs ) and super() , multiple inheritance lines will break, causing runtime errors or uninitialized parent states. 4. Metaprogramming: Custom Metaclasses
To introduce structure, Python provides Abstract Base Classes (ABCs). An ABC is one that describes the requirement that another class have a particular collection of methods without specifying what those methods do. You define an abstract method with the @abstractmethod decorator, and any subclass must implement that method before it can be instantiated.