db.model and python constructors

[Kelly A]

As I understand it you cannot use python constructors when creating an
object that inherits from db.model, so this would not work:

class myClass(db.model):
myProperty = db.StringProperty()
def __init__(self):
tempProperty = something complex.
myProperty = tempProperty

Is the best way to do processing on the creation of objects based on
db.model to create factories that generate the objects then?

[david ignacio]

think about something like this:

class myClass(db.model):
myProperty = db.StringProperty()

def __init__(self, myProperty=None, **kwargs):
if myProperty is None:
myProperty = something cool
super(myClass, self).__init__(myProperty=myProperty, **kwargs)

since what you are doing is replacing the db.model constructor, not
actually calling it anywhere

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[Nick Johnson (Google)]

Hi Kelly,

It is possible to provide a constructor, but not recommended. If you do, make sure to take arbitrary arguments (*args, **kwargs) and pass them to the parent constructor, and bear in mind that the constructor will be called internally when constructing instances restored from the datastore, as well as when you call it explicitly.

In general, though, factory methods are a safer option.

-Nick Johnson

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