[BangPypers] Favorite tips/techniques

[Gopalakrishnan Subramani]

Attributes are stylish, readable, feel native as object compared to
dictionary. Sometimes I use setter methods to override the default
assignments, modify getter to format the values and getter for virtual
attributes for DSL stuffs.


class DictObj(dict):
    def __getattr__(self, key):
        if key.startswith("has_"):
            arr = key.split("_")
            return arr[1] in self

        return self[key]

    def __setattr__(self, key, value):
        self[key] = value


od = DictObj()

od.name = "Nila"

print ("Has Name? ", od.has_name)
print ("Has Age? ", od.has_age)

We have this sort of implementation for functional test verification. We
are into Industrial Automation, we deal with measurement devices like flow,
pressure, density, etc. Each device has got  100+ attributes like tag,
address, current value, calibration etc.

Injecting 'has' and 'is' helps test engineers write unit test based on
device property itself.

if (device.is_calibration_running): # here calibration_running is a value
read from the device or cached and is is applied for dynamic conditions.
     ...

Although it seems like magic, but certainly not a black magic, we have
control over there.

Python must have got similar stuff  like dynamic function hooks, we could
done still better. But we are missing.







On Tue, Sep 10, 2013 at 8:48 PM, BibhasD <me at bibhas.in> wrote:

> I'm just curious. I faced a similar issue before while answering a
> question about Django on StackOverflow. Django turns context variable
> dictionaries into objects with attributes in template. So in one
> question in SO someone posted this question. Had to answer that Django
> doesn't really support distinguishing such keys. So when I saw the same
> thing discussed, thought of throwing it out here. :)
>
> On Tuesday 10 September 2013 08:42 PM, Dhananjay Nene wrote:
> > Ignoring classes for the moment, how likely do you think you would
> > have a dict like that :)
> >
> > On a separate note if you are using primitive types, I cannot think of
> > any scenarios, where not coercing keys to be of the same type would be
> > considered inappropriate (except in case of reverse dicts)
> >
> > On Tue, Sep 10, 2013 at 3:52 PM, Me at Bibhas <me at bibhas.in> wrote:
> >> What would happen for a dictionary like this?
> >>
> >>>>> d = {'1': 'foo', 1: 'bar'}
> >>>>> d
> >> {'1': 'foo', 1: 'bar'}
> >>
> >>
> >> On Tuesday 10 September 2013 10:00 AM, Noufal Ibrahim wrote:
> >>> Shabda Raaj <shabda at agiliq.com> writes:
> >>>
> >>>>
> http://code.activestate.com/recipes/52308-the-simple-but-handy-collector-of-a-bunch-of-named/
> >>>>
> >>>> With api responses after you have parsed the json, you start doing
> things
> >>>> like:
> >>>>
> >>>> api_response["attribute"]
> >>>>
> >>>> I would much prefer to do
> >>>>
> >>>> api_response.attribute
> >>> I generally like to use attributes instead of keys. One additional
> >>> advantage is that I can, if necessary, later convert the attribute into
> >>> a property that does more than just return a value.
> >>>
> >>> [...]
> >>>
> >>>
> >> _______________________________________________
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> >> BangPypers at python.org
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> >
> >
>
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