Python’s magic method
obj.__set_name__(self, owner, name) method is created on an attribute
obj when the class
owner holding the attribute is created.
We call this a “Dunder Method” for “Double Underscore Method” (also called “magic method”). To get a list of all dunder methods with explanation, check out our dunder cheat sheet article on this blog.
Syntax and Minimal Example
object.__set_name__(self, owner, name)
Here’s a minimal example:
class Attribute: pass class My_Class: x = Attribute() # Python calls: x.__set_name__(My_Class, 'x')
x = Attribute() internally causes Python to call
Overriding __set_name__() Example
Let’s override the
__set_name__ magic method on the
class Attribute: def __set_name__(self, owner, name): print('Python is great!') class My_Class: x = Attribute()
In fact, the magic method is called which results in the output:
Python is great!
More Practical Example
The purpose of the magic method
__set_name__(), however, is not to print dummy strings to the Python shell—as you may have guessed already.
💡 Note: The
__set_name__() method is called automatically by Python for every single attribute held by the owner class object when initializing an object—in our previous example an object of type
My_Class. More details here.
__set_name__() method is not called when assigning attributes to an object dynamically—later in the code.
To see what I mean, have a look at this code snippet:
class Attribute: def __set_name__(self, owner, name): print('Python is great!') class My_Class: pass My_Class.x = Attribute() # x.__set_name__() is NOT called!! # <No Output>
Now, you can manually call the
__set_name__() method to run the same routine you’d have run if you’d initialized the attribute in the class definition right away:
class Attribute: def __set_name__(self, owner, name): print('Python is great!') class My_Class: pass My_Class.x = Attribute() # <No Output> My_Class.x.__set_name__(My_Class, 'x') # Python is great!
Where to Go From Here?
Enough theory. Let’s get some practice!
Coders get paid six figures and more because they can solve problems more effectively using machine intelligence and automation. To become more successful in coding, solve more real problems for real people. That’s how you polish the skills you really need in practice. After all, what’s the use of learning theory that nobody ever needs?
You build high-value coding skills by working on practical coding projects!
Do you want to stop learning with toy projects and focus on practical code projects that earn you money and solve real problems for people?
If your answer is YES!, consider becoming a Python freelance developer! It’s the best way of approaching the task of improving your Python skills—even if you are a complete beginner.
Join my free webinar “How to Build Your High-Income Skill Python” and watch how I grew my coding business online and how you can, too—from the comfort of your own home.
While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.
To help students reach higher levels of Python success, he founded the programming education website Finxter.com. He’s author of the popular programming book Python One-Liners (NoStarch 2020), coauthor of the Coffee Break Python series of self-published books, computer science enthusiast, freelancer, and owner of one of the top 10 largest Python blogs worldwide.
His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.