Question

How do I check if two instances of a

class FooBar(object):
    __init__(self, param):
        self.param = param
        self.param_2 = self.function_2(param)
        self.param_3 = self.function_3()

are identical? By identical I mean they have the same values in all of their variables.

a = FooBar(param)
b = FooBar(param)

I thought of

if a == b:
    print "a and b are identical"!

Will this do it without side effects?

The background for my question is unit testing. I want to achieve something like:

self.failUnlessEqual(self.my_object.a_function(), another_object)

Answer 1

If you want the == to work, then implement the __eq__ method in your class to perform the rich comparison.

If all you want to do is compare the equality of all attributes, you can do that succinctly by comparison of __dict__ in each object:

class MyClass:

    def __eq__(self, other) : 
        return self.__dict__ == other.__dict__