Strings

The set of tests on this page is primarily concerned with strings of ASCII characters only. See the Unicode tests page for comparisons involving non-ASCII characters.

Notation: Because some of the examples on this page contain unprintable or invisible characters, a special notation delimited by guillemets, as in , is adopted to represent a single occurance of a Unicode character, in this case U+007B.

Converting Python strings to JSON

These tests exercise some of the basic character handling. For the purposes of these tests, the following Python defintions will be used:

import UserString
UsrStr = UserString.UserString( 'Hello' )

Control characters: Note that JSON requires that all control characters U+0000 through U+001F be escaped, either with \uxxxx or a predefined \ escape code. The python-json module though incorrectly outputs most of the control characters literally without any escaping. Similarly, simplejson does not escape U+001A through U+001F as required.

DEL: On the other hand, although JSON permits the delete character U+007F to be escaped, it does not require it. The demjson and python-json modules choose to output U+007F literally without escaping. The simplejson module escapes it by default, unless it is explicitly told not to (see the Unicode discussion on the next page).

Table 1: Python strings and escape sequences

Test#	from Python	to JSON	demjson	jsonlib	python-cjson	python-json	simplejson
1–1	[""]	[""]	yes	yes	yes	yes	yes
1–2	["Hello"]	["Hello"]	yes	yes	yes	yes	yes
1–3	[ UsrStr ]	["Hello"]	yes	no: error	no: error	no: error	no: error
1–4	["\x00"]	["\u0000"]	yes	yes	yes	no, outputs: ["«U+0000»"]	yes
1–5	["A\x00Z"]	["A\u0000Z"]	yes	yes	yes	no, outputs: ["A«U+0000»Z"]	yes
1–6	["\x08"]	["\b"]	yes	yes	yes	yes	yes
1–7	["\x09"]	["\t"]	yes	yes	yes	yes	yes
1–8	["\x0a"]	["\n"]	yes	yes	yes	yes	yes
1–9	["\x0b"]	["\u000b"]	yes	yes	yes	no, outputs: ["«U+000B»"]	yes
1–10	["\x0c"]	["\f"]	yes	yes	yes	yes	yes
1–11	["\x0d"]	["\r"]	yes	yes	yes	yes	yes
1–12	["\x1a"]	["\u001a"]	yes	yes	yes	no, outputs: ["«U+001A»"]	no, outputs: ["«U+001A»"]
1–13	["\x1f"]	["\u001f"]	yes	yes	yes	no, outputs: ["«U+001F»"]	no, outputs: ["«U+001F»"]
1–14	["\x22"]	["\""]	yes	yes	yes	yes	yes
1–15	["\x27"]	["'"]	yes	yes	yes	yes	yes
1–16	["\x2f"]	["/"]	yes	yes, outputs: ["\/"]	yes	yes	yes, outputs: ["\/"]
1–17	["\x5c"]	["\\"]	yes	yes	yes	yes	yes
1–18	["\x7f"]	["«U+007F»"]	yes	yes, outputs: ["\u007f"]	yes, outputs: ["\u007f"]	yes	yes, outputs: ["\u007f"]

Converting JSON strings to Python

Table 2: JSON strings and escape sequences

Test#	from JSON	to Python	demjson	jsonlib	python-cjson	python-json	simplejson
2–1	[""]	['']	yes	yes	yes	yes	yes
2–2	["Hello"]	['Hello']	yes	yes	yes	yes	yes
2–3	["\b"]	['\x08']	yes	yes	yes	yes	yes
2–4	["\f"]	['\f']	yes	yes	yes	yes	yes
2–5	["\n"]	['\n']	yes	yes	yes	yes	yes
2–6	["\r"]	['\r']	yes	yes	yes	yes	yes
2–7	["\t"]	['\t']	yes	yes	yes	yes	yes
2–8	["\\"]	['\\']	yes	yes	yes	yes	yes
2–9	["\/"]	['/']	yes	yes	no, outputs: ['\\\\/']	yes	yes
2–10	["\""]	['"']	yes	yes	yes	yes	yes

Dealing with invalid JSON strings

The JSON string syntax is much more strict than that of JavaScript. The following tests include strings which are not legal JSON, yet are valid JavaScript. A conforming parser should either raise an error, or should produce the same string value as that of JavaScript.

Table 3: Invalid JSON, but valid JavaScript strings

Test#	from JavaScript	demjson/strict	demjson/loose	jsonlib	python-cjson	python-json	simplejson
3–1	['Hello']	yes: error	almost, outputs: ['Hello']	yes: error	yes: error	yes: error	yes: error
3–2	["\v"]	yes: error	almost, outputs: ['\x0b']	yes: error	no, outputs: ['\\v']	yes: error	yes: error
3–3	["\0"]	yes: error	almost, outputs: ['\x00']	yes: error	no, outputs: ['\\0']	yes: error	yes: error
3–4	["\0123"]	yes: error	almost, outputs: ['\n3']	yes: error	no, outputs: ['\\0123']	yes: error	yes: error
3–5	["\x9A"]	yes: error	almost, outputs: ['\x9a']	yes: error	no, outputs: ['\\x9A']	yes: error	yes: error
3–6	["\e"]	yes: error	almost, outputs: ['e']	yes: error	no, outputs: ['\\e']	yes: error	yes: error
3–7	["\zulu"]	yes: error	almost, outputs: ['zulu']	yes: error	no, outputs: ['\\zulu']	yes: error	yes: error

The following strings are neither valid JSON nor valid JavaScript, and so any compliant parser should reject them with an error.

Table 4: Invalid JSON or JavaScript strings

Test#	Illegal input	demjson/strict	demjson/loose	jsonlib	python-cjson	python-json	simplejson
4–1	["A Z"]	yes: error	no, outputs: [u'A Z']	no, outputs: ['A\nZ']	no, outputs: ['A\nZ']	no, outputs: ['A\nZ']	no, outputs: ['A\nZ']
4–2	["A«U+0000»Z"]	yes: error	no, outputs: ['A\x00Z']	yes: error	no, outputs: ['A\x00Z']	no, outputs: ['A\x00Z']	no, outputs: ['A\x00Z']
4–3	["A«U+001F»Z"]	yes: error	no, outputs: ['A\x1fZ']	no, outputs: [u'A\x1fZ']	no, outputs: ['A\x1fZ']	no, outputs: ['A\x1fZ']	no, outputs: ['A\x1fZ']

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