__new__
__new__ is a Python special method that creates and returns an instance before its initialization by __init__ occurs.
Python How-To
__new__ is Python's special class-level method that creates and returns a new instance before initialization.
- How it is used
- Explains object construction and customizes instance creation when ordinary allocation needs to change.
- How deep it goes
- Explains the sequential call order, returned identity, manual simulation, and subclass customization, while recommending ordinary use of __init__.
- Examples
- Uses Task identity tracing and PokerOrder normalization to demonstrate creation order and custom sorting.
- What you can do after
- Understand instance creation, trace object identity, and customize construction for subclasses such as PokerOrder.
Python Workout: 50 ten-minute exercises
A Python special method responsible for creating and returning a new instance before initialization occurs.
- How it is used
- Clarifies what happens when a class is called and distinguishes object creation from instance initialization.
- How deep it goes
- Explains the creation-to-initialization sequence but stops short of implementing custom __new__.
- Examples
- Uses Foo(10), self.x, and diagrams tracing creation, initialization, attribute assignment, and return.
- What you can do after
- Evaluate ordinary construction correctly and favor __init__ over redefining __new__ in typical classes.
Read how Python Workout: 50 ten-minute exercises explains __new__ →
Python Workout, Second Edition
__new__ is a Python special method that creates and returns a new instance before initialization occurs.
- How it is used
- Explains why __init__ is initialization rather than the method that creates an instance.
- How deep it goes
- Traces creation, initialization, and return, while deferring custom __new__ implementation as rarely necessary.
- Examples
- Uses Foo(10), self.x, and f.x to demonstrate creation followed by attribute initialization.
- What you can do after
- Understand the execution order behind class calls and avoid mistaking __init__ for the instance-creation method.
Related concepts
- objectproduces · A computational object is a runtime entity or structured value representing data, state, or a resource, with properties or operations defined by its programming model.
- initializerused by · An initializer is a function, declaration, or language construct that establishes the initial value or state of an object, value, computation, or process.
- constructor methodcontrasts with · A constructor is a type-associated operation or callable that creates or initializes an instance and establishes its initial state.
- Singleton patternused by · The Singleton pattern restricts a type or component to one shared instance within a defined scope and provides a way to access it.
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