On 2012-09-18 00:46, Dave Angel wrote:
On 09/17/2012 07:34 PM, Terry Reedy wrote:
On 9/17/2012 6:12 PM, Chris Angelico wrote:
On Tue, Sep 18, 2012 at 7:55 AM, Fernando Jiménez
<the.me...@gmail.com> wrote:
Hi guys!
I'm noob in python and I would know how to correctly use the
property. I
have read some things about it but I do not quite understand.
But I think it's a bad habit to use _ to change the visibility of the
attributes as in JAVA.
How to correctly use the property?
<snip>
More examples:
A class has a data attribute that really is a simple attribute, no
property. You define a subclass that needs a calculation for the
attribute. So you use property in the subclass.
A class has an attribute that is a constant that must be computed. You
do not want to compute is unless and until needed.
def get_x(self):
try:
return self._x
except AttributeError:
self._x = calculate_x()
return self._
For a read-only attribute, don't provide a setter. If you do not like
"AttributeError: can't set attribute", provide one with a customized
error.
But I think most of the data attributes in stdlib classes are straight
attributes.
An important difference from every other language I've used: The user
of the attribute does not need to change his code when you decide it
needs reimplementation as a property.
In C++ and java, for example, people will define getter and setter
methods just so they don't have to change them later. Just "in case"
it's needed later.
C# and Delphi (IIRC) also support properties.
--
http://mail.python.org/mailman/listinfo/python-list
