Question

Are there any ways to add a simple implementations for __str__,__eq__,__repr__ to a class?

Basically I want an __eq__ to be just be whether all non prefixed instance variables are equal.

And a __str__/__repr__ that just names each variable and calls str/repr on each variable.

Is there a mechanism for this in the standard library?

Answer 1

You could define a Default mixin:

class Default(object):
    def __repr__(self):
        return '-'.join(
            str(getattr(self,key)) for key in self.__dict__ if not key.startswith('_'))
    def __eq__(self,other):
        try:
            return all(getattr(self,key)==getattr(other,key)
                       for key in self.__dict__ if not key.startswith('_'))
        except AttributeError:
            return False


class Foo(Default):
    def __init__(self):
        self.bar=1
        self.baz='hi'

foo=Foo()
print(foo)
# hi-1

foo2=Foo()
print(foo==foo2)
# True

foo2.bar=100
print(foo==foo2)
# False