PHP->Python JSON issue

Question

What am I doing wrong? Python3:

>>> import json
>>> s = "\"{'key': 'value'}\""
>>> obj = json.loads(s)
>>> obj['key']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: string indices must be integers

Given JSON string is produced by json_encode() from php

Real string: {sessionid:5,file:\/home\/lol\/folder\/folder\/file.ttt}.

UPDATE: Problem is because i transfer json string as command line to shell_exec in php, and read it using sys.argv[1]... So quotes are removed by shell.

PHP Code (which runs python script with shell_exec)

$arg = json_encode(['sessionid' => $session->getId(), 'file' => $filename]);
shell_exec('python3 script.py ' . $arg);

Python code:

import json, sys
s = json.loads(sys.argv[1]) #fails already

paidhima · Accepted Answer · 2015-04-01 17:51:57Z

2

Look at this JSON:

"\"{'key': 'value'}\""

You have a string containing an escaped quote, followed by a dictionary-like object, then an escaped quote. When you try to decode this you wind up with the following:

"{'key': 'value'}"

That's a string, not a dictionary.

answered Apr 1, 2015 at 17:51

paidhima

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9 Comments

Croll Over a year ago

Without this, json.loads raises ValueError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

Daniel Roseman Over a year ago

Because the inner string is not JSON. JSON always has double quotes around keys and values.

Croll Over a year ago

Yep! And such JSON string is produced by json_encode() from php

paidhima Over a year ago

I would look at your object before it's been serialized in PHP then. You need those quotes to be double, or it isn't valid syntax.

Croll Over a year ago

PHP: json_encode(['sessionid' => $session->getId(), 'file' => $filename]) -- python script receives this as a command line argument with shell_exec()

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Croll · Accepted Answer · 2015-04-01 20:19:20Z

1

Kasra answer is correct, ast does the trick, but, additionally i had to 'fix' my string with php - to prevent 'damaging' (by shell?):

php code:

$cmd = json_encode(['sessionid' => $session->getId(), 'file' => $filename]);
$cmd = str_replace('"', '\'', $cmd);
$cmd = str_replace('\\/', '/', $cmd);
$cmd = 'python3 program.py "' . $cmd . '"';
exec($cmd);

python code:

import json, sys, ast  
task = json.loads("\"" + sys.argv[1] + "\"")
task = ast.literal_eval(task)

sessionid = task['sessionid'] # DONE!:)

edited Apr 1, 2015 at 20:19

answered Apr 1, 2015 at 19:11

Croll

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Comments

Kasravnd · Accepted Answer · 2015-04-01 17:53:15Z

0

As your string surrounded by 2 quote that you escaped one of them so after reading the string with json the result will be string,So after that you can use ast.literal_eval to convert your string to dictionary :

>>> obj = json.loads(s)
>>> obj
"{'key': 'value'}"
>>> import ast
>>> new=ast.literal_eval(obj)
>>> new['key']
'value'

answered Apr 1, 2015 at 17:53

Kasravnd

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