How to parse a JSON array in Python

Question

My JSON array is as follows and I would like to build a new string that would output accordingly.

I have a simple function just to see if I can return a value but it's failing with Error was expected string or buffer

def blah(myjson):
    data = json.loads(myjson)
    for item in data:
        result = item['svn_tag']

    return result

JSON:

[{'svn_tag': '20150623r3', 'module': 'api'}, {'svn_tag': '20150624r1', 'module': 'ui'}]

Proposed Output:

api - 20150623r3, ui - 20150623r3

Single quotes are not valid JSON. You have to use double-quotes. — jwodder
– jwodder, Commented Jul 29, 2015 at 20:57
well the interesting thing is that Ansible is returning it w/ single quotes. My JSON in the source file has double quotes but when I return the variable it converts everything to single quotes. — sdot257
– sdot257, Commented Jul 29, 2015 at 20:59
I take it back it is double quotes, the output is just in single quote. — sdot257
– sdot257, Commented Jul 29, 2015 at 21:01

JuniorCompressor · Accepted Answer · 2015-07-29 21:12:50Z

1

The problem is that json wants the strings and field names encoded in double quotes and not single quotes. So either replace manually the single quotes or use ast.literal_eval since the string is also a python valid literal:

import ast

def blah(myjson):
    data = ast.literal_eval(myjson)
    return ', '.join(item['module'] + ' - ' + item['svn_tag'] for item in data)

s = '''[{'svn_tag': '20150623r3', 'module': 'api'}, {'svn_tag': '20150624r1', 'module': 'ui'}]'''
print blah(s)

Result:

api - 20150623r3, ui - 20150624r1

edited Jul 29, 2015 at 21:12

answered Jul 29, 2015 at 21:05

JuniorCompressor

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8 Comments

sdot257 Over a year ago

grrrr so it's telling me there's a Keyerror for module and svn_tag. return ', '.join(item['svn_tag'] for item in data) KeyError: 'svn_tag

JuniorCompressor Over a year ago

Do you use the same string? Otherwise check if svn_tag is defined for each array entry.

sdot257 Over a year ago

i think it's an Ansible thing so ignore the Keyerror. So I'm pretty sure the string/variable that I'm passing in is this [{'svn_tag': '20150624r1_6.36_gameofthrones', 'module': 'ariaapi'}] because if I return the variable that i passed to the function that's what gets displayed. However, running it through the function you have, it's throwing a ValueError: malformed string

JuniorCompressor Over a year ago

This is because the variable isn't a string but an already python array. So skip the whole parsing thing and use ', '.join(item['module'] + ' - ' + item['svn_tag'] for item in variable_name)

sdot257 Over a year ago

Ughhh ... so w/o the data = ast.literal_eval(myjson) line and with only return ', '.join(item['module'] + ' - ' + item['svn_tag'] for item in myjson) yields KeyError: 'module'

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