Re: Python class gotcha with scope?
great, thanks for the quick responses :)
On Jun 21, 2:41 am, Carl Banks wrote:
> On Jun 20, 11:32 pm, billy wrote:
>
> > I don't quite understand why this happens. Why doesn't b have its own
> > version of r? If r was just an int instead of a dict, then it would.
>
> > >>> class foo:
>
> > ... r = {}
> > ... def setn(self, n):
> > ... self.r["f"] = n
> > ...>>> a = foo()
> > >>> a.setn(4)
>
> > >>> b = foo()
> > >>> b.r
>
> > {'f': 4}
>
> r is a class attribute, that is, it is attacted to the class itself.
> Look at what happens when you enter foo.r at the interactive prompt:
>
> >>> foo.r
>
> {'f': 4}
>
> You want an instance attribute, a value attached to the instance of
> the class. You create those in the __init__ method:
>
> class foo:
> def __init__(self):
> self.r = {}
> def setn(self,n):
> self.r["n"] = n
>
> Carl Banks
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Re: Python class gotcha with scope?
On Jun 20, 11:32 pm, billy wrote:
> I don't quite understand why this happens. Why doesn't b have its own
> version of r? If r was just an int instead of a dict, then it would.
>
> >>> class foo:
>
> ... r = {}
> ... def setn(self, n):
> ... self.r["f"] = n
> ...>>> a = foo()
> >>> a.setn(4)
>
> >>> b = foo()
> >>> b.r
>
> {'f': 4}
r is a class attribute, that is, it is attacted to the class itself.
Look at what happens when you enter foo.r at the interactive prompt:
>>> foo.r
{'f': 4}
You want an instance attribute, a value attached to the instance of
the class. You create those in the __init__ method:
class foo:
def __init__(self):
self.r = {}
def setn(self,n):
self.r["n"] = n
Carl Banks
--
http://mail.python.org/mailman/listinfo/python-list
Re: Python class gotcha with scope?
On Jun 21, 2:38 pm, Vincent wrote:
> On Jun 21, 2:32 pm, billy wrote:
>
>
>
> > I don't quite understand why this happens. Why doesn't b have its own
> > version of r? If r was just an int instead of a dict, then it would.
>
> > >>> class foo:
>
> > ... r = {}
> > ... def setn(self, n):
> > ... self.r["f"] = n
> > ...>>> a = foo()
> > >>> a.setn(4)
>
> > >>> b = foo()
> > >>> b.r
>
> > {'f': 4}
>
> > thanks,
>
> > billy
>
> class Foo:
> def __init__(self):
> self.r = {}
> def setn(self,n):
> self.r['f'] = n
>
> a = Foo()
> a.setn(3)
> a.r
> {'f': 3}
> b = Foo()
> b.r
> {}
you defined r as class-level variable.
and i defined r as instance-level variable.
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Re: Python class gotcha with scope?
On Jun 21, 2:32 pm, billy wrote:
> I don't quite understand why this happens. Why doesn't b have its own
> version of r? If r was just an int instead of a dict, then it would.
>
> >>> class foo:
>
> ... r = {}
> ... def setn(self, n):
> ... self.r["f"] = n
> ...>>> a = foo()
> >>> a.setn(4)
>
> >>> b = foo()
> >>> b.r
>
> {'f': 4}
>
> thanks,
>
> billy
class Foo:
def __init__(self):
self.r = {}
def setn(self,n):
self.r['f'] = n
a = Foo()
a.setn(3)
a.r
{'f': 3}
b = Foo()
b.r
{}
--
http://mail.python.org/mailman/listinfo/python-list
Python class gotcha with scope?
I don't quite understand why this happens. Why doesn't b have its own
version of r? If r was just an int instead of a dict, then it would.
>>> class foo:
... r = {}
... def setn(self, n):
... self.r["f"] = n
...
>>> a = foo()
>>> a.setn(4)
>>>
>>> b = foo()
>>> b.r
{'f': 4}
thanks,
billy
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