Hi,
I have two classes with a number of methods that are the same, so I want to
define a super class that holds these methods. But the super class (below
called _Generic) should not be instantiated, because it serves no purpose other
than the DRY principle. I raise a NotImplementedError in case if somebody dares
to instantiate _Generic. Below, only one common method is defined in_Generic,
namely __repr__ (the other ones are __enter__ and __exit__, maybe more, if you
must know). At first I thought I'd need the abc module for this, but this seems
to do the trick. I do not want to enforce concrete implementations of abstract
methods, which is the goal of abc. Is this the way to do this, or this this
quirky code?
import inspect
class _Generic(object):
def __init__(self, *args, **kwargs):
raise NotImplementedError
def __repr__(self):
fmt = []
for arg in inspect.getargspec(self.__init__).args[1:]:
value = getattr(self, arg)
sr = "%r" if isinstance(value, basestring) else "%s"
fmt.append(("%s=" + sr) % (arg, value))
return self.__class__.__name__ + "(" + ", ".join(fmt) + ")"
class Concrete(Generic):
def __init__(self, x=42, y='a'):
self.x = x
self.y = y
class OneMore(Generic):
def __init__(self, w=555, z='foo'):
self.w = w
self.z = z
c = Concrete()
print repr(c)
a = _Generic(666) # NotImplementedError
Thank you!
Albert-Jan
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