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A newbie question about class

newgene newgene at bigfoot.com
Sun Feb 10 12:03:11 EST 2002 
"Mark McEahern" <marklists at mceahern.com> wrote in message news:<mailman.1013306655.4125.python-list at python.org>...
> [newgene]
> > Hi, group,
> >      I have a newbie question about building a class:
> >
> > eg.
> >
> > class A:
> >    def __init__(self,x=None):
> >        self.x=x
> >        if self.x != None:
> >             self.y=x**2
> >        else:
> >             self.y=x**2
> 
> 1.  When comparing to None, it's better to use one of the following:
> 
> 	if x is not None:...
> 	if x is None:...

Could you explain a little more why "is not" is better than "!="? 

> 
> 2.  Consider using property, which is new with Python 2.2 and requires a
> new-style class (thus we subclass from object):
> 
> class A(object):
> 
> 	def __init__(self, x=None):
> 		self._x = x
> 
> 	def getX(self):
> 		return self._x
> 
> 	def setX(self, x):
> 		self._x = x
> 
> 	x = property(getX, setX)
> 
> a = A(1)
> print a.x
> 
> Cheers,
> 
> // mark

Thank you and other experts above. I got the solution for this problem now.


Newgene
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