get/set

[Gerhard Häring]

William Dode wrote in comp.lang.python:
> hi,
> 
> coming from java, i use to do a lot of get set method and make all the
> variable as private.
> 
> class Toto:
> 	def getA(self): return self._a
> 	def setA(self,v): self._a=v
> 	...
> 
> Shall i do like that in python ?

I think you don't need this boilerplate code most of the time. Since
Python 2.2, however, you can mimic the Java behaviour without
resorting to __getattr__/__setattr__. The pyhton.org website with
Guido's introduction to 2.2 features currently seems to be down, but
you can look here for some basic intro for 2.2 features:

http://www.amk.ca/python/2.2/

Your example could then look like:

class Toto(object):
    __slots__ = ["_a"]

    def __init__(self):
        self._a = 5

    def set_a(self, val):
        if val < 5 or val > 10:
            raise ValueError, "val must be in [5;10]"
        self._a = val

    def get_a(self):
        return self._a

    # Third argument is for attribute deletion; None means cannot delete attribute
    a = property(get_a, set_a, None)

x = Toto()
print x.a
x.a = 10
x.a = 11        # raises ValueError
x.b = 5         # raises AttributeError; no such attribute

It also has the advantage that it can be used with GPL software ;-)

Gerhard
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