How to get updated variable in class?

Question

I have the following code:

class MyClass:
    some_variable = None

    def __init__(self, args):
        data = infile.read()
        self.some_variable= int.from_bytes(data[0:4], byteorder="big", signed=False)


if __name__ == "__main__":
    with open("input_file", "rb") as infile:
        MyClass(infile)
        print(MyClass.some_variable)

This prints None, how do I do this?

Answer 1

You need to access an instance of the class not the class itself

if __name__ == "__main__":
    with open("input_file", "rb") as infile:
        my_class = MyClass(infile)
        print(my_class.some_variable)

Answer 2

def __init__(self, args):
    data = infile.read()
    self.some_variable= int.from_bytes(data[0:4], byteorder="big", signed=False)

So your self.some_variable is called an "instance's attribute", and you can access it from an instance:

my_instance_of_MyClass = MyClass(infile)
print(my_instance_of_MyClass.some_variable)

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I would suggest you to read this to better understand the difference between class variables and instance variables.