On 6 Aug., 21:46, John Krukoff <[EMAIL PROTECTED]> wrote: > On Wed, 2008-08-06 at 05:50 -0700, Slaunger wrote: > > 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 > > -- > >http://mail.python.org/mailman/listinfo/python-list > > Are you really sure this is what you want to do, and that a less tricky > serialization format such as that provided by the pickle module wouldn't > work for you?
Well, it is not so much yet for serialization (although i have not yet fully understood the implications), it is more because I think the eval(repr(x))==x is a nice unit test to make sure my constructor and equals method is implemented correctly (that I have rememebered all attributes in their implementations). As mentioned above, I may go for a more pragmatic approach, where i only use repr if it "standard" imported Cheers, Slaunger > > -- > John Krukoff <[EMAIL PROTECTED]> > Land Title Guarantee Company- Skjul tekst i anførselstegn - > > - Vis tekst i anførselstegn - -- http://mail.python.org/mailman/listinfo/python-list
