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Options for controlling the jyson decoding process.

Default mode is strict compliance.

If you use jyson in it's default mode, which is strict mode, then parsing will be performed strictly according to the original JSON specification. If an error is found, a JSONDecodeError exception is raised, giving the location of the offending construct in the document, as described on the jyson error reporting page.

For a discussion of compliance with RFC 4627 , see the jyson comparison page.

Why have options?

One nice feature of JSON is that it's syntax is valid in more than one language. As well being valid javascript (and thus also ECMAScript ) , JSON documents are also valid python .

Python permits the user to represent data in different ways. For example, the integer constant 42 could be represented in hexadecimal as 0x2a, an also as the octal constant 052. When representing characters in strings, the letter a can be represented as \x61 (hexadecimal escape), or as \u0061 (unicode escape). This capability allows the user to directly bypass the character encodings of their terminals and viewing programs, and represent unambiguously what they mean.

Another important issue is that of dangling commas in JSON documents. It is often the case that JSON documents are written by hand (when they are template documents, for example), and contain hard to spot mistakes. It is arguable whether JSON parsers should accept such (strictly invalid) documents : I wrote jyson to accept dangling commas, at user option.

These are the options you can use to control parsing with jyson.

How to use these options

All decode options are passed to the loads method as keyword arguments with boolean values True or false., like this

>>> from com.xhaus.jyson import JysonCodec as json
>>> json.loads("42.0", accept_any_primary_datum=True)
42.0
>>>

Which instructs jyson to accept any top level datum in the document, as described below.

Option: strict_mode

This option controls all of the options listed below. If you set this option to true, then jyson is set into strict JSON compliance mode, and all of the options below are set to false.

If you set this option to false., then all non-JSON-conformant options listed below will be set to true.

The default value for the strict_mode option is true.

Option: accept_any_primary_datum

This option controls whether or not jyson will accept documents that contain something other than a JSON object or array as the top level object. For example, this document is strictly invalid

42.0

because the top level object is a number, which is a breach of RFC 4627 .

If you parse with this option set to true, then the above document would be accepted, as follows

>>> from com.xhaus.jyson import JysonCodec as json
>>> json.loads("42.0")
com.xhaus.jyson.JSONDecodeError: JSON expressions must strictly be either objects or lists: position=4
>>> json.loads("42.0", accept_any_primary_datum=True)
42.0
>>>

The default value for accept_any_primary_datum is false.

Option: accept_dangling_commas

If this is option is true, then dangling commas in a JSON document will be accepted.

>>> from com.xhaus.jyson import JysonCodec as json
>>> json.loads("[1,]")
com.xhaus.jyson.JSONDecodeError: Commas after last element of array not accepted: position=4
>>> json.loads("[1,]", accept_dangling_commas=True)
[1]
>>> json.loads('{"hello":"world",}')
com.xhaus.jyson.JSONDecodeError: Commas after last entry of object not accepted: position=18
>>> json.loads('{"hello":"world",}', accept_dangling_commas=True)
{'hello': 'world'}
>>>

The default value for accept_dangling_commas is false.

Option: accept_shell_style_comments

This option controls whether jyson accepts shell style comments, as would be seen in a python program

>>> from com.xhaus.jyson import JysonCodec as json
>>> json.loads("""# my json document
... [1]
... # end of my json document""")
com.xhaus.jyson.JSONDecodeError: Shell style comments are not accepted: position=1
>>> json.loads("""# my json document
... [1]
... # end of my json document""", accept_shell_style_comments=True)
[1]
>>>

The default value for accept_shell_style_comments is false.

Option: accept_single_quoted_strings

This option controls whether jyson accepts quotes delimited with single quote characters ('is this a string?'). Such string delimiters are valid in both python and javascript, but not in JSON.

>>> from com.xhaus.jyson import JysonCodec as json
>>> json.loads("['Hello World!']")
com.xhaus.jyson.JSONDecodeError: Single quoted strings are not accepted: position=2
>>> json.loads("['Hello World!']", accept_single_quoted_strings=True)
['Hello World!']
>>>

The default value for accept_single_quoted_strings is false.

Option: accept_hex_char_escapes

This option controls whether jyson accepts hexadecimal character escapes, as are commonly used in python strings ("A" == "\x41")

>>> from com.xhaus.jyson import JysonCodec as json
>>> json.loads('["This is a capital \\x41"]')
com.xhaus.jyson.JSONDecodeError: Hexadecimal escapes for characters are not accepted: position=22
>>> json.loads('["This is a capital \\x41"]', accept_hex_char_escapes=True)
['This is a capital A']
>>>

The default value for accept_hex_char_escapes is false.

Option: accept_hexadecimal_integers

This option ontrols whether jyson accepts hexadecimal integer constants, which are indicated with a leading 0x and are case insensitive: e.g. 255=0xFF=0xff.

>>> from com.xhaus.jyson import JysonCodec as json
>>> json.loads('[255,0xFF,0xff]')
com.xhaus.jyson.JSONDecodeError: Hexadecimal integers are not accepted.: position=9
>>> json.loads('[255,0xFF,0xff]', accept_hexadecimal_integers=True)
[255, 255, 255]
>>>

The default value for accept_hexadecimal_integers is false.

Option: accept_octal_integers

This option controls whether jyson accepts octal integer constants, which are indicated with a leading 0: e.g. 0100=64=0x40.

>>> from com.xhaus.jyson import JysonCodec as json
>>> json.loads('[0100,64]')
com.xhaus.jyson.JSONDecodeError: Octal integers are not accepted.:position=5
>>> json.loads('[0100,64]', accept_octal_integers=True)
[64, 64]
>>>

The default value for accept_octal_integers is false.

Option: accept_junk_after_data

This option controls whether jyson accepts extraneous data after the primary object

>>> json.loads('{"an": "object"} ["and some more stuff"]')
com.xhaus.jyson.JSONDecodeError: Only whitespace is permitted after the primary datum: not '[': position=18
>>> json.loads('{"an": "object"} ["and some more stuff"]', accept_junk_after_data=True)
{'an': 'object'}
>>>

The default value for accept_junk_after_data is false.

Updated by Alan Kennedy about 15 years ago ยท 1 revisions