The python rationale is "We are all consenting adults.".
You shoukd change "tens" to "_tens" and "ones" to "_ones", in order to syntacticly mark these attributes as internal. If someone not consenting, wants to mess with your internal representation, it's his fault.
HTH, Gerald
Marcus Goldfish schrieb:
I'd like advice/opinions on when it is appropriate to do attribute/property validation in python. I'm coming from a C#/Java background, where of course tons of "wasted" code is devoted to property validation. Here is a toy example illustrating my question:
# Example: mixing instance attributes with properties. Is it pythonic to # validate property data in setters? Since tens and ones are never # validated, the class can be "broken" by setting these directly class SillyDecimal(object): """A silly class to represent an integer from 0 - 99.""" def __init__(self, arg=17): if isinstance(arg, tuple): self.tens = arg[0] self.ones = arg[1] else: self.number = arg
def getNumber(self): return self.tens*10 + self.ones def setNumber(self, value): if value < 0 or value > 99: raise ArgumentException("Must in [0, 99]") self.tens = value // 10 self.ones = value % 10 number = property(getNumber, setNumber, None, "Complete number, [0-99]")
x = SillyDecimal() x.number, x.tens, x.ones # returns (17, 7, 1)
Even though "tens", "ones" and "number" all appear as attributes, only "number" has its input validated. Since the class is designed to only hold numbers 0 - 99, one can 'break' it by setting self.tens=11, for example. Should tens and ones be made into full-fledged properties and validated? Should number have no validation? Is it more pythonic to encapsulate tightly, or rely on "responsible use."
Marcus
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