On 01/31/2014 06:28 PM, Terry Reedy wrote:
Construct a house:
Clear and grade house site.
Bring in power and water.
Built temporary structures.
Built foundation.
Built house on foundation.
For most classes, __new__ stops with the foundation -- the bare object object
(with the class name slapped onto it). A
*house* is not constructed until the house is constructed on top of the
foundation.
On the ground programming has the dividing line at:
immutable objects --> everything done in __new__
mutable objects --> everything done in __init__
Typically, immutable objects are not created in Python code because, well, it's really dang hard (__slots__, anyone?),
but one still needs to understand how __new__ and __init__ go together to do the more interesting stuff (such as having
__new__ return a dynamically selected subclass, which still needs to be (or not be) __init__ed).
--
~Ethan~
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