Best practise implementation for equal by value objects

[Slaunger]

Hi,

I am new here and relatively new to Python, so be gentle:

Is there a recommended generic implementation of __repr__ for objects
equal by value to assure that eval(repr(x)) == x independet of which
module the call is made from?

Example:

class Age:

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

    def __eq__(self, obj):
        self.age == obj.age

    def __repr__(self):
        return self.__class__.__name__ + \
               "(%r)" % self.age

age_ten = Age(10)
print repr(age_ten)
print eval(repr(age_ten))
print eval(repr(age_ten)).age

Running this gives

Age(10)
Age(10)
10

Exactly as I want to.

The problem arises when the Age class is iomported into another module
in another package as then there is a package prefix and the above
implementation of __repr__ does not work.

I have then experimented with doing somthing like

    def __repr__(self):
        return self.__module__ + '.' + self.__class__.__name__ +
"(%r)" % self.age

This seems to work when called from the outside, but not from the
inside of the module. That is, if I rerun the script above the the
module name prefixed to the representation I get the following error

Traceback (most recent call last):
  File "valuetest.py", line 15, in <module>
    print eval(repr(age_ten))
__main__.Age(10)
  File "<string>", line 1, in <module>
NameError: name '__main__' is not defined

This is pretty annoying.

My question is: Is there a robust generic type of implementation of
__repr__ which I can use instead?

This is something I plan to reuse for many different Value classes, so
I would like to get it robust.

Thanks,
Slaunger