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Subject: Re: pymongo and attribute dictionaries
From: Travis Griggs <travisgriggs@gmail.com>
In-Reply-To: <CALwzid=W=R3A9nS1ZFUNduR0WRdMnLdu2g9q+E753DSfEUBy8Q@mail.gmail.com>
Date: Wed, 4 Feb 2015 12:16:24 -0800
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Xref: csiph.com comp.lang.python:85228


> On Feb 4, 2015, at 9:22 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
>=20
> On Wed, Feb 4, 2015 at 9:50 AM, Travis Griggs <travisgriggs@gmail.com> =
wrote:
>> I really like pymongo. And I really like Python. But one thing my =
fingers really get tired of typing is
>>=20
>> someDoc[=E2=80=98_=E2=80=99id=E2=80=99]
>>=20
>> This just does not roll of the fingers well. Too many =E2=80=9Creach =
for modifier keys=E2=80=9D in a row. I would rather use
>>=20
>> someDoc._id
>>=20
>> Googling shows that I=E2=80=99m not the first to want to do this in =
the general sense (e.g. =
http://stackoverflow.com/questions/4984647/accessing-dict-keys-like-an-att=
ribute-in-python).
>>=20
>> Arguments aside of whether this should or shouldn=E2=80=99t be done, =
I want to know how I might solve this with Python. Consider it an =
academic pursuit.
>>=20
>> The problem I have is not how to do the AttributeDictionary subclass, =
there are plenty of those examples. The problem is that the pymongo APIs =
already return dictionaries. In a language (Smalltalk, Objective-C, =
Ruby) that supports class extensions, that would be my first tool of =
choice to solve this problem. I=E2=80=99d just extend Dictionary to =
behave the way I want and be done with it. I can=E2=80=99t do that in =
Python though. I guess I could make my own module that subclasses the =
relevant pymongo classes, and do super() calling implementations of all =
of the relevant methods, coercing the return type. That is a maintenance =
headache though.
>>=20
>> What are my options, if any?
>=20
> You could construct the AttributeDictionary by copying the dict
> returned from pymongo. The question then is whether the copying would
> be too expensive or not.
>=20
> Alternately, you could just wrap the dictionaries returned by pymongo
> in an object. Something like this should be all you need:
>=20
> class AttrDictWrapper(object):
>    def __init__(self, the_dict):
>        self.__dict__ =3D the_dict
>=20
>>>> d =3D AttrDictWrapper({'spam': 42, 'ham': False})
>>>> d.spam
> 42
>>>> d.ham
> False
>=20

Yes, that is clever. So if you wanted to minimize the amount of typing =
you had to do at all of your pymongo API call sites, what strategy would =
you use to keep that relatively terse?

Is the following the right approach to take?

class Doc(object):
    def __init__(self, target):
        self.__dict__ =3D target

and then something like

for doc in client.db.radios.find({=E2=80=99_id': {=E2=80=99$regex=E2=80=99=
: =E2=80=98^[ABC]'}}):
    pprint(doc)

changes to

for doc in ((Doc(d) for d in client.db.radios.find({=E2=80=99_id': =
{=E2=80=99$regex=E2=80=99: =E2=80=98^[ABC]'}})):
    pprint(doc)

Are there other approaches? Feel free to impress me with evil abuses in =
the interest of academic enrichment...