Hi Martin
What about something like this:
class A(SageObject):
def __new__(cls, a, b=None, c=None):
if isinstance(a, A):
print "just use a"
return a
else:
print "create new instance"
return super(A, cls).__new__(cls, a, b, c)
def __init__(self, a, b=None, c=None):
if isinstance(a, A):
print "no init required"
return
print "init"
Regards
Jonas
On 29.03.2015 18:35, 'Martin R' via sage-devel wrote:
Since the above appears to be a very difficult question (:-), I'm going
to add another one - which is actually mentioned in the thread title,
but I somehow forgot to ask...
Suppose I have a class A with an __init__ method taking a single
mandatory argument:
class A(SageObject):
def __init__(self, a, b=None, c=None):
What I'd like to achieve is that A(a) yields a, if a is an instance of
A. I have read a bit about unique representation and
CachedRepresentation, etc., but what I really want to achieve here is, I
hope, much simpler.
I don't want to use CachedRepresentation, since the arguments of
__init__ would be expensive to cache.
Many thanks,
Martin
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