A Consolidated List of 20 Most Common Magic Methods

Magic methods: The gem of Python OOP.

Avi Chawla

Nov 05, 2023

One of the things I (and many Python programmers) love the most about Python OOP is its Magic Methods.

Magic Methods offer immense flexibility to define the behavior of class objects in specific scenarios.

They are prefixed and suffixed with double underscores, such as __len__, __str__, and many more.

On a side note, that is why they are also called “Dunder methods” — short for Double UNDERscore.

They make our classes more intuitive and easier to work with.

As a result, awareness about them is extremely crucial for developing elegant and intuitive pipelines.

The visual below summarizes the 20 most used Magic Methods in Python.

In my experience, these are possibly the only 20 magic methods you would ever need in most Python projects utilizing OOP.

__new__:
- This method is invoked before __init__ to allocate memory to an object.
- In most cases, we wouldn’t need it.
- Yet, at times, I have used this to define checks and allocate memory only when certain conditions are met.
- Another common usage is to define singleton classes — classes with only one object.
__init__:
- Most common in this list.
- This is invoked after memory allocation to assign value to an object’s attributes.
__str__:
- Executing print(obj) outputs the memory address of the object, which is not interpretable.
- Defining this method lets us print the object in a readable format.
__int__: Invoked when we execute → int(obj).
__len__: Invoked when we execute → len(obj).
__call__:
- Invoked when a class object is called as a function → obj().
- We covered it here before.
__getitem__: Invoked when an object is indexed → obj[key].
__setitem__: Invoked when an object is indexed and a value is set → obj[key]=value.
__delitem__: Invoked when an object’s index is deleted → del obj[key].
__contains__: Invoked when the in operator is used → item in obj.
__bool__: Invoked when an object is used in a boolean context → if obj or bool(obj).
__iter__: Invoked when we iterate over an object → for x in obj.
__eq__: Invoked when == operator is used to compare two objects → obj1 == obj2.
__ne__: Invoked when != operator is used to compare two objects → obj1 != obj2.
__gt__:
- Invoked when > operator is used to compare two objects → obj1 > obj2.
- Other than __gt__, we also have:
  - __lt__: less than.
  - __le__: less than or equal to.
  - __ge__: greater than or equal to.
__add__: Invoked when two objects are added → obj1 + obj2.
__mul__: Invoked when two objects are multiplied → obj1 * obj2.
__abs__: Invoked when we compute the absolute value of an object: abs(obj).
__neg__: Invoked when the unary operator - (minus) is used on an object → -obj.
__invert__: Invoked when ~ (tilde) operator is used to invert an object → ~obj.

That’s it.

Now you know the most common Magic methods in Python and how they are used.

👉 Over to you: Did I miss any common magic methods? If yes, which one(s)? Let me know :)

👉 If you liked this post, don’t forget to leave a like ❤️. It helps more people discover this newsletter on Substack and tells me that you appreciate reading these daily insights.