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Re: pymongo and attribute dictionaries

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  Re: pymongo and attribute dictionaries Travis Griggs <travisgriggs@gmail.com> - 2015-02-04 12:16 -0800
    Re: pymongo and attribute dictionaries Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-02-05 09:52 +1300

#85228 — Re: pymongo and attribute dictionaries

> On Feb 4, 2015, at 9:22 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> 
> 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
>> 
>> someDoc[‘_’id’]
>> 
>> This just does not roll of the fingers well. Too many “reach for modifier keys” in a row. I would rather use
>> 
>> someDoc._id
>> 
>> Googling shows that I’m not the first to want to do this in the general sense (e.g. http://stackoverflow.com/questions/4984647/accessing-dict-keys-like-an-attribute-in-python).
>> 
>> Arguments aside of whether this should or shouldn’t be done, I want to know how I might solve this with Python. Consider it an academic pursuit.
>> 
>> 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’d just extend Dictionary to behave the way I want and be done with it. I can’t 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.
>> 
>> What are my options, if any?
> 
> 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.
> 
> Alternately, you could just wrap the dictionaries returned by pymongo
> in an object. Something like this should be all you need:
> 
> class AttrDictWrapper(object):
>    def __init__(self, the_dict):
>        self.__dict__ = the_dict
> 
>>>> d = AttrDictWrapper({'spam': 42, 'ham': False})
>>>> d.spam
> 42
>>>> d.ham
> False
> 

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__ = target

and then something like

for doc in client.db.radios.find({’_id': {’$regex’: ‘^[ABC]'}}):
    pprint(doc)

changes to

for doc in ((Doc(d) for d in client.db.radios.find({’_id': {’$regex’: ‘^[ABC]'}})):
    pprint(doc)

Are there other approaches? Feel free to impress me with evil abuses in the interest of academic enrichment...

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#85230

Travis Griggs wrote:
> for doc in client.db.radios.find({’_id': {’$regex’: ‘^[ABC]'}}): pprint(doc)
> 
> changes to
> 
> for doc in ((Doc(d) for d in client.db.radios.find({’_id': {’$regex’:
> ‘^[ABC]'}})): pprint(doc)
> 
> Are there other approaches? Feel free to impress me with evil abuses in the
> interest of academic enrichment...

You could encapsulate some of that in a helper function such as

def docs(source):
    for d in source:
       yield Doc(d)

then your example becomes

for doc in docs(client.db.radios.find({’_id': {’$regex’: ‘^[ABC]'}})):
    pprint(doc)

-- 
Greg

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