__set__() magic method sets a given attribute on an instance of a class holding the attribute (=owner class) to a new value. When setting the attribute through the owner class, Python dynamically executes the attribute’s
__set__() method to override its
value on the given
object.__set__(self, instance, value)
For example, if you create a class
Person with an attribute of type
Name (and instances
person.name = 42 would result in calling the
__set__() method to obtain the result.
💡 Terminology: The
name attribute of type
Name in our example is called a descriptor.
In the following, you can see a minimal example of a descriptor
name attribute defining the
__set__ magic method.
class Name: def __set__(self, instance, value): self.value = value class Person: name = Name() alice = Person() # The following calls __set__(alice.name, 'Alice Python'): alice.name="Alice Python" print(alice.name.value) # Alice Python
Let’s go through the code next:
- You create a
Personclass with one attribute name of type
- You define the
Nameclass as a descriptor by overriding the
__set__method takes over responsibility each time you’re about to assign a value to an attribute of type
- Python translate the expression
__set__(alice.name, 'Alice Python').
- In this magic method call, you set the
name.valueattribute to the string
'Alice Python'passed as an argument. This is the output of this code snippet.
Now, you have an initial intuition. To learn more about how descriptors work, I’d recommend you check out the in-depth official Python tutorial that is a great resource on the topic! 🙂
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!
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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.
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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.