The Basics

A property is created by assigning the result of a built-in function to a class attribute:

attribute = property(fget, fset, fdel, doc)

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None of this built-in’s arguments are required, and all default to None if not passed; such operations are not supported, and attempting them will raise an exception. When using them, we pass fget a function for intercepting attribute fetches, fset a function for assignments, and fdel a function for attribute deletions; the doc argument receives a documentation string for the attribute, if desired (otherwise the property copies the docstring of fget, if provided, which defaults to None). fget returns the computed attribute value, and fset and fdel return nothing (really, None).

This built-in call returns a property object, which we assign to the name of the attribute to be managed in the class scope, where it will be inherited by every instance.