[Baypiggies] A properties and obj.__dict__ question

[Glen Jarvis]

Thanks everyone!

I went with the format example. It was exactly what I was looking for:

http://docs.python.org/library/string.html#formatexamples

In fact, before I tried to look it up or before I asked for help, I was
writing things like:

%({obj}.name)s

The format module makes it even cleaner. Python so fits in your brain, I
love it. I also love that I learned about the format module now....  w00t!

Again, thanks for all the help everyone!



Glen



On Thu, Sep 8, 2011 at 8:51 PM, Glen Jarvis <glen at glenjarvis.com> wrote:

> I have a question that is hard to ask without involving code. I reduced my
> project down to a tiny test case (as follows).
>
> As you see, the following code will work and access the variables within
> the class successfully. However, it's a cheat, using the internal attributes
> instead of the properties (as properties don't show in __dict__).
>
> The objective is to have a large string with different fields. The fields
> happen to all be members of my class.  So, I could hard code things like
> this:
>
> message = """
>     Name: %s
>     Address: %s
>     %s, %s  %s
>  """ % {obj.name, obj.address, obj.city, obj.state, obj.postal_code}
>
> But, as each of the items are properties of the class, I'd like to be more
> dynamic, like this:
>
> message = """
>     Name: %(obj.name)s
>     Address: %(obj.address)s
>     %(obj.city)s, %(obj.state)s  %(obj.postal_code)s
>  """ % obj
>
> I can do this with normal attributes, like the following:
>
> message = """
>     Name: %(name)s
>     Address: %(address)s
>     %(city)s, %(state)s  %(postal_code)s
>  """ % obj.__dict__
>
> However, these attributes in my case are properties and don't show in the
> __dict__.
>
> Here's a runnable piece of code to demonstrate:
>
>
> =-=-=-=-=-=-=-  Start of Working Code -=-=-=-=-=-=-=-=-=-
> class Piggie(object):
>     def __init__(self):
>         """A demo for a BayPIGgies question"""
>         self._name = None
>         self._address = None
>
>     @property
>     def name(self):
>         return self._name
>
>     @name.setter
>     def name(self, value):
>         if isinstance(value, basestring):
>             value = value.strip()
>         self._name = value
>
>     @property
>     def address(self):
>         return self._address
>
>     @address.setter
>     def address(self, value):
>         if isinstance(value, basestring):
>             value = value.strip()
>         self._address = value
>
>     def __unicode__(self):
>         if self.name is None:
>             return u"Nameless Person"
>         else:
>             return self.name
>     __str__ = __unicode__
>
>
> f = Piggie()
> f.name = 'Glen'
>
>
> message = """
>     Obviously, this is silly for only two fields like this.
>
>     But, it's a very reduced test case to demo a problem from a
>     much larger project.
>
>     Name: %(_name)s
>     Address:  %(_address)s
>  """ %  f.__dict__
>
> print message
> =-=-=-=-=-=-=-  Start of Working Code -=-=-=-=-=-=-=-=-=-
>
>
> This works, as the output below shows. However, only by accessing the
> internal attributes of the class directly, not using the property accessors.
> How can I do something like this, but with property accessors. Something
> like dir(f) or f.__property_dict__ that just has the properties.
>
> Run:
>
>
>     Obviously, this is silly for only two fields like this.
>
>     But, it's a very reduced test case to demo a problem from a
>     much larger project.
>
>     Name: Glen
>     Address:  None
>
>
>
> Run with the properties used:
>
> Traceback (most recent call last):
>   File "x.py", line 48, in <module>
>     """ %  f.__dict__
> KeyError: 'name'
>
>
> Thanks, for letting me share :)
>
>
>
> Glen
> --
> Things which matter most must never be at the mercy of things which matter
> least.
>
> -- Goethe
>



-- 
Things which matter most must never be at the mercy of things which matter
least.

-- Goethe
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