"Ben" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
<snip>
> This seems to work without any errors. But bizzarely I find that
> whatever my record number, the instance of "my_class" is appended to
> every list. So in this case
>
> self.mop_list[0].my_list.append(my_class(Some data for the
> constructor))
>
> I would expect to append an instance of my_class to
> self.mop_list[0].my_list
>
> But annoyingly
>
> self.mop_list[0].my_list
> self.mop_list[3].my_list
> self.mop_list[7].my_list
>
> all have an instance of my_class created and appended to them. This is
> really confusing and quite annoying - I don't know whether anyone out
> there can make head or tail of what I'm doing wrong?
Well, it's a little bit difficult, but I think I actually know what's going
on. You probably need some code that looks something like this, to ensure
each object has it's own, independent list:
class record:
def __init__(self, init_list=None):
self.my_list = []
if init_list is not None:
self.my_list.extend(init_list)
Here's what I think you are doing, and below should make it clear why that
doesn't work:
class record:
def __init__(self, init_list=[]):
That list above, the default initializer is constructed just once (when the
def statement executes)!
>>> class record:
... def __init__(self, init_list=[]):
... self.my_list = init_list
...
>>> r1 = record()
>>> r1.my_list
[]
>>> r2 = record()
>>> r2.my_list
[]
>>> r2.my_list.append('boo!')
>>> r1.my_list
['boo!']
>>>
>>> l1 = range(1, 4)
>>> l1
[1, 2, 3]
>>> r1 = record(l1)
>>> r2 = record(l1)
>>> r1.my_list
[1, 2, 3]
>>> r2.my_list
[1, 2, 3]
>>> r1.my_list.append(42)
>>> l1
[1, 2, 3, 42]
>>> r1.my_list
[1, 2, 3, 42]
>>> r2.my_list
[1, 2, 3, 42]
>>>
--
http://mail.python.org/mailman/listinfo/python-list
