Class object attributes

Sometimes we need values which will be the same for all instances of the class. Imagine I'm writing some code for a geographical information system (GIS). The earth is abstracted as an ellipsoid, with a defined semi major axis, and semi minor axis. These will not change.

I can define a class object attribute in the same way that we used to define constants in other programming languages. I add the following code before the constructor.

# Define a class object attribute, it will be the same for any instance of the class
    semi_major_axis = 6378137
    semi_minor_axis = 6356752

We don't need to use the self keyword, as these values will be the same for every instance of the class. The following code at the end tests that this works.

# Instantiate the class
my_object = MyTemplate("John", True)
# Check the object
print(my_object.semi_major_axis, my_object.semi_minor_axis)

To generalize the template, change

  • semi_major_axis to class_object_attribute1

  • semi_minor_axis to class_object_attribute2

Then change the print statement to accommodate these changes and retest.

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