Python: inherit Set objects

[CHW]

Hello,

I want to create a class implementing cyclotomic cosets which inherits from Set (http://docs.python.org/library/stdtypes.html#set-types-set-frozenset).

I would like to inherit from Set, because I need methods from Set like intersection and so on, this would avoid me to reimplement the whole stuff.

But my method which I used in the past to inherit for example int or tuple did not work and I couldn't find any documentation helping me there...

Here is my code which fails:

class K(set):
"The class of cyclotomic cosets."
def __new__(self, i, n):
s = [i,]
if i != 0:
j = (2 * i) % n
while j != i:
s.append(j)
j = (2 * j) % n
return set.__new__(self, s)

If I would substitute the last line by "return set(s)" this would work, but then I create a set, not a K object.

Does someone has a suggestion how to solve this problem?

Regrads,
CHW

[spillz]

how about __init__ instead of __new__?



class K(set):
"The class of cyclotomic cosets."
def __init__(self, i, n):
s = [i,]
if i != 0:
j = (2 * i) % n
while j != i:
s.append(j)
j = (2 * j) % n
set.__init__(self, s)

print K(2,3)

[CHW]

Thank you :)

Exactly what I wanted!