Hello all,
As part of a project i'm doing (mostly for the fun of it), I have a class which creates a sort of wrapper around any object to make it suitable for use in a custom container. However, if the class receives an already wrapped object, I want it to just return the object (same id and everything as the original). Now, the following seems to work in the __init__ method (due to output), but then it disappears as soon as the __init__ method is left:
class Node: ... def __init__(self, cargo=None, prev=None, next=None, nod=False): """x.__init__(...) initializes x; see x.__class__.__doc__ for signature""" if not isinstance(cargo, Node) or nod: self.cargo = cargo self.prev = prev self.next = next else: self = cargo print id(self), id(cargo) print self.cargo
a = Node(1) b = Node(a)
12932600 12932600 1
id(b)
12960632
Any ideas on why this happens, or suggestions as to how to implement the behavior I'm looking for (in which b and a would refer to the same object, have the same id, etc.), would be greatly appreciated.
Thanks in advance, Orri
Orri,
Maybe you could use a factory. It would allow you to simplify your Node class, and encapsulate the instantiation behavior you want outside the class.
class Node(object): def __init__(self,cargo=None,prev=None,next=None): self.cargo = cargo self.prev = prev self.next = next
def factory(cargo=None,prev=None,next=None):
if isinstance(cargo,Node):
return cargo
else:
return Node(cargo,prev,next)
n1 = factory(1) print id(n1) n2 = factory(n1) print id(n2)
Good luck,
Rich _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
