[Python-ideas] REG: Scope of a better API for JSON parser

[Anoop Thomas Mathew]

On 6 April 2014 10:56, Andrew Barnert <abarnert at yahoo.com> wrote:

> From: Anoop Thomas Mathew <atmb4u at gmail.com>
> Sent: Saturday, April 5, 2014 7:58 PM
>
>
> >I went through the state of cpython JSON parser, and found that there is
> a scope for improvement in the parser interface.
>
>
> >I have been thinking of implementing a class called QuickParse inside
> json module, which will tidy up the process of finding node, and cuts down
> a number of for loops, if .. else and try ... except blocks.
> >
> >For eg.
> >
> >sample_json = {
> >'name' : 'John Doe',
> >'age' : 45,
> >'level': 'Expert',
> >'languages': [
> >              'C',
> >              'C++',
> >              'Python',
> >              'Clojure'
> >              ],
> >    'account details': {
> >         'account number': 1233312312,
> >         'account balance': 1000000000.00
> >     }
> >}
>
> That's not a JSON object, that's just a plain old Python dict. It doesn't
> even have anything to do with JSON (except the variable name, which is
> misleading).
>
> And you don't need to "parse" a dict; you just use [] or get on it.
>
> Even if you actually had a JSON string or file serializing this dict, you
> could get exactly the dict by just calling json.loads or json.load on it.
> It's hard to imagine anything simpler than that.
>
> Compare your desired code to the equivalents that already work today:
>
> >json_doc = QuickParse(sample_json)
> >
> >json_doc.get(["name"])
> >'John Doe'
>
> sample_json['name']
> ... or ...
> sample_json.get('name')
>
> Note that, besides the simple and more flexible access, you already didn't
> need that extra step of building a QuickParse object.
>
> >json_doc.get(["languages", 2])
>
> > 'C++'
>
>
> sample_json['languages'][2]
>
> >json_doc.get(["account details", "account balance"])
> >1000000000.00
>
>
> sample_json['account details']['account balance']
>
> >json_doc.get(["notpresent"])
> >None
>
>
> sample_json.get('notpresent')
>

I completely agree to your point. But what if the document is of something
like this:

person['country']['state']['city']['county']



> >This is something I've been using in many number of projects, due to the
> complexity of the json documents these days. Also, there is a plan to
> provide option to use functions for iterating over the document, as well as
> selection ranges for expected values.
>
>
> You can already iterate over a dict, and again, I can't imagine how
> anything you design will be simpler than what you can already do.
>
> Also, at the start, you suggested that this would be an improvement to the
> JSON _parser_. But the stuff you showed has nothing to do with the parser.
> Unless the result of calling QuickParse is not JSON parsed into something
> dict-like, but rather something that holds the original JSON and re-parses
> it for each "get" request?
>
> I'm going to assume that the whole bit about parsing is a red herring, and
> the part you actually want is the ability to call the "get" function with
> multiple keys and recursively walk the structure. I'm sure you can find
> recipes for that on ActiveState or PyPI, but it's also very trivial to
> write yourself:
>
>

>     def get(obj, *keys, default=None):
>         for key in keys:
>             try:
>                 obj = obj[key]
>             except LookupError:
>                 return default
>         return obj


I apologize for making the previous mail complicated. You have pinned down
what I was suggesting.

My suggestion is to integrate something similar as you suggested above to
the cpython json module.

Won't that be a good feature for developers to be able to write code
without worrying if it going to fail and writing may try.. except or if
else to handle those edge cases?

I definitely feel that it would be a great feature which is common for any
program which is parsing multilevel json documents.


>
Now, without needing any kind of special object, you can write this:
>
>     get(sample_json, 'languages', 2)
>
>
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