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pythonclassattributes

setting attribute in __init__ with method in python?

I'm learning python. I'd like for self.characteristic to be set to 5 when an object of the class is created. I'm using the set.characteristic method, because in reality there would be a bunch of calculations to reach the value 5. I'd expect the output of my code below to be 5, but I get None. Why? Thanks!

class AnyClass:

    def __init__(self):
        self.characteristic = self.set_characteristic()


    def set_characteristic(self):
        # in reality would do a bunch of calculations 
        self.characteristic = 5


obj = AnyClass()
print(obj.characteristic)

# Output: None 
# Expected output: 5
Solution

  • You forgot to return the desired value in your function.

    def set_characteristic(self):
    # in reality would do a bunch of calculations 
    return 5

    When you do not return a value, function returns None.