OOP in Python

[Chris Barker]

Alex Martelli wrote:
> A class may have attributes (it's also possible to use a module
> attribute, aka 'global variable', of course).  Example:
> 
> class Totalizer:
>     grand_total = 0
>     def inc(self):
>         self.__class__.grand_total += 1
>     def dec(self):
>         self.__class__.grand_total -= 1
>     def __str__(self):
>         return "Total is %d"%self.__class__.grand_total

Or make the class attribute a mutable type, and the syntax gets simpler:

class Totalizer:
    grand_total = [0]
    def inc(self):
        self.grand_total[0] += 1
    def dec(self):
        self.grand_total[0] -= 1
    def __str__(self):
        return "Total is %d"%self.grand_total[0]

# two separate instances
one = Totalizer()
two = Totalizer()

# but they share state!  Try:
one.inc()
two.inc()
one.inc()
two.inc()
print one

Nice trick, though, Alex, I hadn't yet discovered that one.

-Chris

-- 
Christopher Barker,
Ph.D.                                                           
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