Parse javascript object declaration which doesn't use strings for property names (using python and BeautifulSoup)

Question

I'm doing something very similar to what this user was doing: trying to load a javascript object declaration into a python dictionary. However, unlike that user, the property names aren't enclosed in quotes.

>>> simplejson.loads('{num1: 1383241561141, num2: 1000}')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/lalalal/site-packages/simplejson/__init__.py", line 385, in loads
    return _default_decoder.decode(s)
  File "/Users/lalalal/site-packages/simplejson/decoder.py", line 402, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/Users/lalalal/site-packages/simplejson/decoder.py", line 418, in raw_decode
    obj, end = self.scan_once(s, idx)
simplejson.decoder.JSONDecodeError: Expecting property name: line 1 column 1 (char 1)

It'd be just splendid if I had the correct JSON notation:

>>> simplejson.loads('{"num1": 1383241561141, "num2": 1000}')
{'num1': 1383241561141, 'num2': 1000}

But, I don't. How can I work around this? Maybe it comes down to something as simple as a regex?

Edit: This regex that Martijn wrote has me halfway there, it just doesn't work if I have trailing whitespace after the braces which happens in some of my example data, e.g. { num1: 1383241561141, num2: 1000}'

i would use a regexp to quote the keys, then parse it as JSON. (/, (\w)+:/g, ', "$1":') and then manually cleanup the string for the first and last key using string methods. that way JSON still does the heavy lifting and you just need to scrub a few predictable strings in a predictable way. — dandavis
– dandavis, Commented Nov 2, 2013 at 18:55
@dandavis What's that snippet supposed to be? A call to re.sub? — 2rs2ts
– 2rs2ts, Commented Nov 2, 2013 at 18:59
its the args to a call to JS's replace method. python should have something related, it's just admittedly been a long time since i used python, forgive me. — dandavis
– dandavis, Commented Nov 2, 2013 at 19:06
No worries. It threw me off because their regex grammar is slightly different, but I understand the approach. — 2rs2ts
– 2rs2ts, Commented Nov 2, 2013 at 19:12

orip · Accepted Answer · 2013-11-02 18:20:02Z

0

Some libraries like RSON support parsing the so-called "relaxed" JSON notation.

Depending on the actual keys, and if you don't care about the security implications (never use this on external input), eval may give you a functioning dictionary as well.

answered Nov 2, 2013 at 18:20

orip

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2 Comments

2rs2ts Over a year ago

I'd like not to use another library, and unfortunately, I can't use eval in this case (not secure!). But thank you nonetheless.

2rs2ts Over a year ago

I was unable to find a solution in pure Python, so I am accepting this answer since it would fix the problem for others.

dandavis · Accepted Answer · 2013-11-02 19:03:53Z

0

one simple way to do it in js:

'{num1: 1383241561141, num2: 1000}'   // the string
  .trim()                             // remove whitespace
  .slice(1,-1)                        // remove endcap braces
  .trim()                             // remove whitespace
  .split(/\s*,\s*/).map(function(a){  // loop through each comma section names as a
     var p=a.split(/\s*:\s*/);        // split section into key/val segments
     this[p[0]]=p[1];                 // assign val to collection under key
     return this;                     // return collection
},{})[0];                             // grab the return once (same on each index)

This routine returns a live object that stringifys like this:

{
    "num1": "1383241561141",
    "num2": "1000"
}

note the string numbers, you can loop through the object again and Number(val) those keys back to real numbers if need be.

answered Nov 2, 2013 at 19:03

dandavis

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4 Comments

2rs2ts Over a year ago

Unfortunately, I'm forced to do this in python, but thank you for the js snippet :)

dandavis Over a year ago

ahh, i didn't see that you need it in python... well, now that you can see a routine that works, translate it to python. i know python has the pieces you need, and it's what, 6 lines of code?

2rs2ts Over a year ago

Yes, exactly. I think I have to worry about commas and colons in my val strings, though. I might be missing how those splits work in javascript (I'm new to it), but, I think they'd trip up on that, right?

dandavis Over a year ago

@2rs2ts: well your demo data works fine with a naive approach. you could do a char-by-char parser, that's actually kinda fun and not as hard as it sounds, but i think the RegExp to JSON route is the simplest if you can get it to take...

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