Python Gotcha's?

[Steven D'Aprano]

On Thu, 05 Apr 2012 11:06:11 +0000, Duncan Booth wrote:

> Steven D'Aprano <steve+comp.lang.python at pearwood.info> wrote:
> 
>> JSON expects double-quote marks, not single:
>>     v = json.loads("{'test':'test'}")  fails v =
>>     json.loads('{"test":"test"}')  succeeds
>> 
>> 
> You mean JSON expects a string with valid JSON? Quelle surprise.

Actually, on further thought, and on reading the JSON RFC, I have decided 
that this is a design bug and not merely a gotcha.

The relevant section of the RFC is this:


4.  Parsers

   A JSON parser transforms a JSON text into another representation.  A
   JSON parser MUST accept all texts that conform to the JSON grammar.
   A JSON parser MAY accept non-JSON forms or extensions.


http://www.ietf.org/rfc/rfc4627.txt


So a valid parser is permitted to accept data which is not strictly JSON. 
Given that both Javascript and Python (and I would argue, any sensible 
modern language) allows both single and double quotation marks as 
delimiters, the JSON parser should do the same. Failure to take advantage 
of that is a design flaw.

Of course, the RFC goes on to say that a JSON generator MUST only 
generate text which conforms to the JSON grammar. So a conforming 
implementation would be perfectly entitled to accept, but not emit, 
single-quote delimited strings.

-- 
Steven