Ast.literal_eval vs json.dumps

Question

I have a dictionary that is stored in the db field as a string. I am trying to parse it into a dict, but json.loadsgives me an error.

>>> c.iframe_data
u"{u'person': u'Annabelle!', u'csrfmiddlewaretoken': u'wTE9RZGvjCh9RCL00pLloxOYZItQ98JN'}"

# json fails
>>> json.loads(c.iframe_data)
Traceback (most recent call last):
ValueError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

# ast.literal_eval works
>>> ast.literal_eval(c.iframe_data)
{u'person': u'Annabelle!', u'csrfmiddlewaretoken': u'wTE9RZGvjCh9RCL00pLloxOYZItQ98JN'}

Why does json fail and ast.literal_eval work? Preferred than another?

Answer 1

jsonfailed because your value is c.iframe_datanot valid JSON . In a jsonstring, the document string is quoted in double quotation marks, and there is nothing similar uto converting strings to unicode. Use means deserializing a document into json.loads(c.iframe_data)jsonc.iframe_data

ast.literal_eval , eval input. Python , .

?

Answer 2

u"{u'person': u'Annabelle!', u'csrfmiddlewaretoken': u'wTE9RZGvjCh9RCL00pLloxOYZItQ98JN'}" Python, Javascript Object Notation, -:

bad = {u'person': u'Annabelle!', u'csrfmiddlewaretoken': u'wTE9RZGvjCh9RCL00pLloxOYZItQ98JN'}
SyntaxError: Unexpected string
good = {'person': 'Annabelle!', 'csrfmiddlewaretoken': 'wTE9RZGvjCh9RCL00pLloxOYZItQ98JN'}
Object {person: "Annabelle!", csrfmiddlewaretoken: "wTE9RZGvjCh9RCL00pLloxOYZItQ98JN"}

yaml :

>>> a = '{"person": "Annabelle!", "csrfmiddlewaretoken": "wTE9RZGvjCh9RCL00pLloxOYZItQ98JN"}'
>>> json.loads(a)
{u'person': u'Annabelle!', u'csrfmiddlewaretoken': u'wTE9RZGvjCh9RCL00pLloxOYZItQ98JN'}
>>> import ast
>>> ast.literal_eval(a)
{'person': 'Annabelle!', 'csrfmiddlewaretoken': 'wTE9RZGvjCh9RCL00pLloxOYZItQ98JN'}
>>> import yaml
>>> a = '{u"person": u"Annabelle!", u"csrfmiddlewaretoken": u"wTE9RZGvjCh9RCL00pLloxOYZItQ98JN"}'
>>> yaml.load(a)
{'u"person"': 'u"Annabelle!"', 'u"csrfmiddlewaretoken"': 'u"wTE9RZGvjCh9RCL00pLloxOYZItQ98JN"'}
>>> a = u'{u"person": u"Annabelle!", u"csrfmiddlewaretoken": u"wTE9RZGvjCh9RCL00pLloxOYZItQ98JN"}'
>>> yaml.load(a)
{'u"person"': 'u"Annabelle!"', 'u"csrfmiddlewaretoken"': 'u"wTE9RZGvjCh9RCL00pLloxOYZItQ98JN"'}

Answer 3

json.loads JSON, . u'...' , , . json.dumps , json.loads.

, json.loads(string) json.dumps(object), ast.literal_eval(string) () repr(object).

JSON is good because it is portable - there are parsers for it trivially available in almost any language. Therefore, if you want to send JSON to the Javascript interface, you will have no problems.

ast.literal_eval is not portable, but it is a bit richer: you can use tuples, sets, and dicts whose keys are not limited to strings, for example.

Also json.loadssignificantly faster thanast.literal_eval .