Class static variables

[Guillaume]

> > I'm writing a tool to translate a variety of OO
> > programming languages. Especially I target Python
> > but I am hesitating about the way to define
> > class-scope static variables. Could you suggest me
> > what is the best and natural form ?
> >
> > Example: MyClass { static int a; }
> > - MyClass_a
> > - accessors + global var
> > - any other form
> MyClass.a will work unless it is a function. (class attributes that
are
> functions are magically turned into instance methods) For example:
>
> class MyClass:
>     #define class attribute
>     a = 0
>     def method(self):
>         #use class attribute
>         do_something_with(MyClass.a)
>
> #use class attribute outside of MyClass
> do_something_else_with(MyClass.a)

Thanx for the answer but...

>>> class CA:
...     a=0
...
>>> b=CA()
>>> b.a
0
>>> b.a=2
>>> c=CA()
>>> c.a
0
>>> b.a
2

# c.a should be 2 and not 0 if a is a static attribute.

>>> class CB(CA):
... 	pass

>>> CB.a=3
>>> CB.a
3
>>> CA.a
0

# here a big problem. the attribute is not inherited...

So for all these reasons, I think I will use __getattr__ and __setattr__
Here is the code I should generate for managing static vars.
Fortunately, there is no need to change the python access for reading.

class A:
	def __setattr__(self,name,value):
		print "A: set "+name+" %s" % value
		try:
			A.__dict__[name]
			A.__dict__[name]=value
			return None
		except KeyError:
			self.__dict__[name]=value

# static vars for A
A.x="XX"
A.w="WW"

class B(A):
	# instance vars for B
	z=None
	def __setattr__(self,name,value):
		print "B: set "+name+" %s" % value
		try:
			B.__dict__[name]
			B.__dict__[name]=value
			return None
		except KeyError:
			A.__setattr__(self,name,value)

# static vars for B
B.y="YY"

a=A()
b=B()

b.z="ZZ"

print b.z
print b.w

print a.x
a.x="XXXX"
print a.x
print b.y
b.y="YYYY"
print b.y
print b.x

try:
	print b.v
except AttributeError:
	print "v is not defined..."





Sent via Deja.com http://www.deja.com/
Before you buy.