> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Python __init__ Method
The `__init__` method is a special method (often referred to as a "dunder" or double-underscore method) in Python that acts as the instance initializer. It is automatically invoked by the Python runtime immediately after an object is instantiated in memory, serving to initialize the newly created object's state by binding attributes to the specific instance.
## Syntax and Signature
The method is defined within a class block. Its signature must include at least one parameter, conventionally named `self`, which represents the bound instance being initialized.
```python theme={"dark"}
class Definition:
def __init__(self, arg1, arg2):
self.arg1 = arg1
self.arg2 = arg2
```
## Technical Mechanics
* **Initialization vs. Construction:** Unlike constructors in languages like C++ or Java, `__init__` does not allocate memory or create the object. The actual object creation is handled by the `__new__` method. The `__new__` method returns an uninitialized instance, which is then passed as the first argument (`self`) to `__init__` for state mutation.
* **Return Type Constraint:** The `__init__` method must strictly return `None`. Attempting to return any other value will result in a `TypeError` at runtime. Its sole purpose is to mutate the `self` object, not to yield a new value.
* **Implicit Invocation:** When a class is called as a function (e.g., `instance = Definition(val1, val2)`), Python internally translates this into a two-step process:
1. `obj = Definition.__new__(Definition, val1, val2)`
2. `if isinstance(obj, Definition): obj.__init__(val1, val2)`
## Inheritance Behavior
When dealing with class hierarchies, Python does not automatically invoke the `__init__` method of a superclass if the subclass overrides it. If a subclass defines its own `__init__` method, it must explicitly invoke the superclass's initializer using the `super()` proxy object to ensure the inherited state is properly initialized.
```python theme={"dark"}
class BaseClass:
def __init__(self):
self.base_state = 1
class DerivedClass(BaseClass):
def __init__(self):
# Explicitly invoke the superclass initializer
super().__init__()
self.derived_state = 2
```
If the subclass does not define an `__init__` method, it inherits the `__init__` method from its superclass via standard Method Resolution Order (MRO), and the superclass initializer is called implicitly upon instantiation.
Tired of Poor Python Skills? Fix That With Deep Grasping!
Learn More
