how to copy a Python object

[Schüle Daniel]

mitsura at skynet.be wrote:
> Already thanks for the reply,
> 
> but how to write your own copy operator? Won't you always be passing
> referrences to new_obj?

for example this would work

 >>> class X(object):
...     def __init__(self,lst):
...             self.lst = lst
...     def copy(self):
...             return X(self.lst[:])
...     def __str__(self):
...             return "lst has id %i" % id(self.lst)
...
 >>> x=X([1,2,3])
 >>> y=x.copy()
 >>> print x
lst has id 1078097132
 >>> print y
lst has id 1078097228


but I don't like that in this case self.lst must be passed
through __init__
I can think of another variant

 >>> class Y(object):
...     def fill(self):
...             self.lst = [randint(i*10,(i+1)*10) for i in xrange(5)]
...     def __repr__(self):
...             return "lst has id = %i" % id(self.lst)
...     def copy(self):
...             ret = Y()
...             ret.lst = self.lst[:]
...             return ret
...
 >>> from random import randint
 >>> y=Y()
 >>> y.fill()
 >>> y
lst has id = 1078097452
 >>> print y
lst has id = 1078097452
 >>> x=y.copy()
 >>> x
lst has id = 1078097004

... anyone?
are there better approaches?

Regards, Daniel