Hi,
I'm been trying to create some custom classes derived from some of
python's built-in types, like int and list, etc. I've run into some
trouble, which I could explain with a couple simple examples. Lets say
I want an int-derived class that is initilized to one greater than what
it's constructor is given:
class myint(int):
def __new__(cls, intIn):
newint = int(intIn+1)
return int.__new__(cls, newint)
print myint(3), myint(10)
Okay, seems to do what I want. Now, lets say I want a list class that
creates a list of strings, but appends "_" to each element. I try the
same thing:
class mylist(list):
def __new__(cls, listIn):
newlist = list()
for i in listIn:
newlist.append(str(i) + "_")
print "newlist: ", newlist
return list.__new__(cls, newlist)
print mylist(("a","b","c"))
Doesn't seem to work, but that print statement shows that the newlist is
what I want... Maybe what I return from __new__ is overwritten in
__init__? Could someone enlighten me as to why - and why this is
different than the int case?
Thanks,
Ken
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