Python instances

[EuGeNe]

henrikpierrou at hotmail.com wrote:
> Hi,
> 
> How do python instances work?
> Why does the code at the end of my posting produce this output:
> 
> list in a:
> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
> list in b:
> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
> 
> instead of
> 
> list in a:
> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
> list in b:
> []
> 
> ----------------------------
> 
> class MyClass:
>     list = []
> 
>     def add(self, x):
>         self.list.append(x)
> 
>     def printer(self):
>         print self.list
> 
> a = MyClass()
> b = MyClass()
> 
> for n in range(10):
>     a.add(n)
> 
> print "list in a:"
> a.printer()
> print "list in b:"
> b.printer()
> 
> /H
> 

because list is a class member not an instance member (not sure about 
the vocabulary) if in __init__ you set self.list=[] you'll get the 
result you want! By declaring list=[] in the class it is shared between 
all instances!

-- 
EuGeNe

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