Python JSON encoding

Question

I m trying to encode data to JSON in Python and I been having a quite a bit of trouble  I believe the problem is simply a misunderstanding    I m relatively new to Python and never really got familiar with the various Python data types  so that s most likely what s messing me up    Currently I am declaring a list  looping through and another list  and appending one list within another   import simplejson  json data      apple    cat      banana    dog      pear    fish     x   simplejson loads data     gt  gt  gt  typeError  expected string or buffer    x   simplejson dumps stream     gt  gt  gt     apple    cat      banana    dog      pear    fish      - shouldn t JSON encoded strings be like     apple    cat     banana   dog      So I either     I don t understand JSON Syntax I don t understand the Pythons JSON module s  I m using an inappropriate data type

User · Answer

The data you are encoding is a keyless array, so JSON encodes it with [] brackets. See www.json.org for more information about that. The curly braces are used for lists with key/value pairs.

From www.json.org:

JSON is built on two structures:

A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array. An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.

An object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by , (comma).

An array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by , (comma).

User · Answer

So  simplejson loads takes a json string and returns a data structure  which is why you are getting that type error there   simplejson dumps data  comes back with       apple    cat      banana    dog      pear    fish       Which is a json array  which is what you want  since you gave this a python array   If you want to get an  object  type syntax you would instead do   gt  gt  gt  data2     apple   cat    banana   dog    pear   fish    gt  gt  gt  simplejson dumps data2     pear    fish    apple    cat    banana    dog      which is javascript will come out as an object

User · Answer

Try   import simplejson data     apple    cat    banana   dog    pear   fish   data json      apple    cat    banana   dog    pear   fish     simplejson loads data json    outputs data simplejson dumps data    outputs data joon   NB  Based on Paolo s answer

User · Answer

JSON uses square brackets for lists      one    two    three      and curly brackets for key value dictionaries  also called objects in JavaScript    one  1   two   b      The dump is quite correct  you get a list of three elements  each one is a list of two strings   if you wanted a dictionary  maybe something like this   x   simplejson dumps dict data    gt  gt  gt    pear    fish    apple    cat    banana    dog     your expected string      apple    cat     banana   dog      isn t valid JSON   A

User · Answer

Python lists translate to JSON arrays  What it is giving you is a perfectly valid JSON string that could be used in a Javascript application  To get what you expected  you would need to use a dict    gt  gt  gt  json dumps   apple    cat    banana   dog    pear   fish       pear    fish    apple    cat    banana    dog

User · Answer

I think you are simply exchanging dumps and loads     gt  gt  gt  import json  gt  gt  gt  data      apple    cat      banana    dog      pear    fish      The first returns as a  JSON encoded  string its data argument    gt  gt  gt  encoded str   json dumps  data    gt  gt  gt  encoded str     apple    cat      banana    dog      pear    fish       The second does the opposite  returning the data corresponding to its  JSON encoded  string argument    gt  gt  gt  decoded data   json loads  encoded str    gt  gt  gt  decoded data   u apple   u cat     u banana   u dog     u pear   u fish     gt  gt  gt  decoded data    data True

User · Answer

In simplejson  or the library json in Python 2 6 and later   loads takes a JSON string and returns a Python data structure  dumps takes a Python data structure and returns a JSON string  JSON string can encode Javascript arrays  not just objects  and a Python list corresponds to a JSON string encoding an array  To get a JSON string such as    apple   cat    banana   dog     the Python object you pass to json dumps could be   dict apple  cat   banana  dog     though the JSON string is also valid Python syntax for the same dict  I believe the specific string you say you expect is simply invalid JSON syntax  however

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