Update a object variable when called

Question

I am learning python, For sure a stupid question but I cannot find any answer.

I have an object

class ant(object):

    def __init__(self, age):
        self.age = 0

    def update_age(self)
        self.age += 1

pebbles = myant(25)

#check age
print pebbles.age

Now what I want to do is that every time someone checks pebble.age, pebbles automatically runs update_age() internally. Is it possible to do it? or every time I have to check pebbles_age I have to write:

pebbles.update_age()
print pebbles.age.

Thanks a lot

jonrsharpe · Accepted Answer · 2015-09-29 10:31:03Z

4

You could implement this using a property:

class Ant(object):  # note leading uppercase, per style guide (PEP-8)

    def __init__(self):  # you ignore the age parameter anyway
        self._age = 0

    def update_age(self):
        self._age += 1

    @property
    def age(self):
        self.update_age()
        return self._age

This makes age read-only, and increments correctly:

>>> an_ant = Ant()
>>> an_ant.age
1
>>> an_ant.age
2
>>> an_ant.age = 10

Traceback (most recent call last):
  File "<pyshell#5>", line 1, in <module>
    an_ant.age = 10
AttributeError: can't set attribute

edited Sep 29, 2015 at 10:31

answered Sep 29, 2015 at 10:17

jonrsharpe

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