What do __double_underscores__ mean in Python?
In Python, when you see names with double underscores (like __init__, __str__, or even __name__), they serve special purposes.
What do __double_underscores__ mean?
Names with double underscores before and after (also called "dunder methods") are special or magic methods used by Python behind the scenes.
They’re part of Python’s object-oriented features and allow you to customize how your objects behave.
Examples of Common __dunder__ Methods:
| Dunder Method | What It Does |
|---|---|
__init__() |
Called when you create a new object (constructor) |
__str__() |
Called when you use print() on an object |
__repr__() |
Called when you use repr() or in debugging |
__len__() |
Makes your object work with len() |
__getitem__() |
Lets you use square brackets [] like a list |
__name__ |
A built-in variable to check if script is run directly or imported |
✨ Example:
Output:
Here, __init__() sets the name, and __str__() defines how the object looks when printed.
What about names like __secret_var?
These usually indicate name mangling, where Python changes the name slightly to avoid accidental access or override (often used in classes for "private" variables).
🔐 Tip:
Not all double underscore names are meant for you to define. Stick to ones documented in the official Python docs unless you're customizing behavior intentionally.