What is the Python equivalent of Comparables in Java?

Question

I have a dictionary of the following form:

{ <Category('Simulate', 'False', 'False', 'False', 'INTERMEDIATE')>: {'link': u'/story/4/tvb-adapters-simulator-simulatorAdapter/SimulatorAdapter', 'name': u'Simulate'}, 
  <Category('View Results', 'True', 'False', 'True', 'INTERMEDIATE')>: {'link': '/story/step/3', 'name': u'View Results'}, 
  <Category('Analyze', 'True', 'False', 'False', 'FINAL')>: {'link': '/story/step/2', 'name': u'Analyze'}}

Category is a class representing an instance from a database. Now I have the following instance:

    <Category('Analyze', 'True', 'False', 'False', 'FINAL')>

Now this is not the same instance. By this I mean, I get all the values from the database and create the dictionary. Then after a while I get an id and retrieve the instance from the database. Now they are not the same objects. I now have to check if it's in the dictionary, but:

instance in disctionary

Will return false. Now I could go the ugly way and iterate over the dictionary checking if all the values match, however does Python have a more clever way to do this? I mean something like the equivalent of Comparable in Java?

Answer 1

First: use True and False (boolean properties) instead of 'True' and 'False' (string properties).

Generally, you can make everything comparable in Python. You just have to define specific methods (like __eq__, __lt__, etc.) for your class.

So, let's say I want to compare instances of class A, and the comparison should be just case-insensitive string comparison of s member:

class A(object):
    def __init__(self, s=''):
        self.s = s

    def __eq__(self, other):
        return self.s.lower() == other.s.lower()

a = A('aaaa')
b = A('AAAA')
print a == b # prints True
b = A('bbbb')
print a == b # prints False