HELP : class and variables

[vincent delft]

Sorry if my question is stupid.
I've missed something with classes.
Can you explain the following ?
class test:
var1=1
var2=2
res=var1+var2

t=test()
print t.res[color=blue][color=green]
>> 3[/color][/color]
t.var1=6
print t.res[color=blue][color=green]
>> 3[/color][/color]

??????????????? ???
I though that everithing is memory zones.
Why it's not 8 ?

Thanks

[Bruno Desthuilliers]

Re: HELP : class and variables

vincent delft wrote:[color=blue]
> Sorry if my question is stupid.
> I've missed something with classes.
> Can you explain the following ?
> class test:
> var1=1
> var2=2
> res=var1+var2
>
> t=test()
> print t.res
>[color=green][color=darkred]
>>>3[/color][/color][/color]

Until here, t.var1 means test.var1 (class variable)
[color=blue]
> t.var1=6[/color]

From here, you created a new instance variable for object t, named
var1. It hides test.var1.
[color=blue]
> print t.res
>[color=green][color=darkred]
>>>3[/color][/color][/color]

What would you expect ?
1/ assigning to t.var1 does not modify test.var1
2/ modifiying test.var1 would not modify test.res anyway ! Guess why ?


Try this instead :[color=blue][color=green][color=darkred]
>>> class test:[/color][/color][/color]
.... def __init__(self):
.... # create instance variables
.... self.var1 = 1
.... self.var2 = 2
.... def res(self):
.... return self.var1 + self.var2
....[color=blue][color=green][color=darkred]
>>> t = test()
>>> t.res()[/color][/color][/color]
3[color=blue][color=green][color=darkred]
>>> t.var1 = 6
>>> t.res()[/color][/color][/color]
8

Bruno

[Bertel Lund Hansen]

Re: HELP : class and variables

vincent delft skrev:
[color=blue]
>Can you explain the following ?[/color]

Yes.
[color=blue]
>class test:
> var1=1
> var2=2
> res=var1+var2[/color]
[color=blue]
>t=test()
>print t.res[color=green][color=darkred]
>>> 3[/color][/color][/color]
[color=blue]
>t.var1=6
>print t.res[color=green][color=darkred]
>>> 3[/color][/color][/color]

Changing var1 does not change res.

You might like to make it a function instead:

class Test:
var1=1
var2=2
def res (self):
return self.var1+self. var2

t=Test()
t.var1=6
print t.res()

I learned in Java to give classes names with the first letter
capitalized. I find that a useful convention.

--
Bertel, Denmark