lazy_init_with_decorator.py

# Even better

def lazy_property(fn):
    '''Decorator that makes a property lazy-evaluated.
    '''
    attr_name = '_lazy_' + fn.__name__

    @property
    def _lazy_property(self):
        if not hasattr(self, attr_name):
            setattr(self, attr_name, fn(self))
        return getattr(self, attr_name)
    return _lazy_property

class Person:
    def __init__(self, name, occupation):
        self.name = name
        self.occupation = occupation
        
    @lazy_property
    def relatives(self):
        # Get all relatives
        relatives = ...
        return relatives