class Age:
def __init__(self, years=None):
if years is None: self.years=0
else: self.years=years
def __setattr__(self, key, value):
if key == "years":
if value < 0:
print "ERROR-Years cannot be less than zero, setting to zero"
self.years=0
return
self.__dict__[key]=value
return
if __name__=="__main__":
a=Age()
#
# Following will print zero because it is the default
#
print a.years
#
# Try to set negative
#
a.years=-1
#
# Other attributes work just fine
#
a.yyy=10
Larry Bates
Steve wrote:
> Hi,
>
> Read this:
> http://www.python.org/2.2.3/descrintro.html#property
>
> If you still don't understand or are confused about it's usage, ask here.
>
> Hint: Suppose you need to create an Age class with a 'years' attribute
> and ensure that, (assuming I create an object a = Age())
> 1) when one tries to access 'a.years', a '0' would be returned even if
> the value was not set or was set to a negative value, and
>
> 2) If a value is assigned to the 'years' attribute, we should check
> for negative values.
>
> HTH
> Regards
> Steve
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