concept of creating structures in python
joe at strout.net
Fri Dec 12 17:07:21 CET 2008
On Dec 12, 2008, at 9:00 AM, Steve Holden wrote:
>> Change the default value of ds_obj here to None. Otherwise, you will
>> certainly confuse yourself (there would be just one default object
>> shared among all instances).
> Joe missed a piece out here. If you change the signature of your
> D.__init__() to read
> def __init__(self, dataName='ND', index = 0, ele_obj=None):
> then you need to insert the following code at the top of the method:
> if ele_obj is None:
> ele_obj = E()
Yes, if you really need to guarantee that ele_obj is not None, then
this is the way to do it.
Of course this would mean that you can't get a None ele_obj even by
passing it in explicitly as the parameter value -- if you need to
support that as well, then the solution is a little more complex.
Perhaps best in that case would be to just not give ele_obj any
default value at all, so it becomes a required parameter.
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