When do I use classmethods?

Question

I was able to complete the exercise dream_vacation.py:

# Below is a class called DreamVacation that holds a location and list of activities.
# Create a @classmethod called rome that will return a new DreamVacation instance with cls() with the following arguments:
# location = 'Rome' and activities list = ['visit the Colosseum', 'Eat gelato'].
# Hint: The classmethod should take cls instead of self as an argument.

class DreamVacation:
    def __init__(self, location, activities):
        self.location = location
        self.activities = activities
    # insert your code here
    @classmethod
    def rome(cls):
        return cls('Rome', ['visit the Colosseum', 'Eat gelato'])

So I understand that classmethods take 'cls' instead of self and act on the class instead of the instance. I'm trying to understand conceptually when I would use this? When is acting on the class better than acting on the instance?

Answer 1 · 2020-06-11T19:00:40Z

June 11, 2020 7:00pm

A situation like the one in this challenge is a good example of when you might use a class method. You would call this before you have an instance (so an instance method would not be possible), and it creates a new instance and returns it.

vacation = DreamVacation.rome()  # get a new instance pre-loaded with data about Rome

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Nathan Garcia

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When do I use classmethods?

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Steven Parker

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