php to python inter-process communication with large data by json

Question

my php code:

<?php
$data = array('as', 'df', 'gh');
$result=shell_exec("start test.py ".escapeshellarg(json_encode($data)));
?>

test.py code:

import sys
import json
try:
    print json.loads(sys.argv[1])
except:
    print "ERROR"
print
raw_input()

it's failing to try and showing ERROR. while if change my python code to this:

import sys
try:
    data=sys.argv[1]
except:
    print "ERROR"
print data,
raw_input()

i'm getting the output as: [ as , df , gh ]

as i'm passing a json encoded data, i should be able to decode it with python's json.loads() method. but why it's not working?

Can you post the output from your PHP code? In other words, print out the exact string that's being passed to the shell. — Jud, Nov 19 '13 at 20:42
with `echo escapeshellarg(json_encode($data));` i'm getting output `"[ as , df , gh ]"` — RatDon, Nov 19 '13 at 20:50
That's not valid json. at bare minimum it should be `["af","df","gh"]` after json_encode, and `'["af","df","gh"]'` after escapeshellarg — Marc B, Nov 19 '13 at 21:03
@MarcB what's the solution. i'm just calling library functions, nothing else. i want to send a associative array created by a html form and pass it to python. but with json encoding not working what can i do? — RatDon, Nov 19 '13 at 21:12
check into why your json_encode is screwing up so badly. if that's really what yours is producing, you've got a majorly buggy install. — Marc B, Nov 19 '13 at 21:13
@MarcB with deleting `escapeshellarg` and writing just `echo json_encode($data);` i'm getting a output `{"1":"as","2":"df","3":"gh"}` and in python `{1:as,2:df,3:gh}` for `$data = array("1"=>"as","2"=>"df","3"=>"gh");` — RatDon, Nov 19 '13 at 21:20
ok. so it's creating a JS object (`{}`) instead of an array (`[]`). Probably because you're quoting your array keys in the original array definition, so that json_encode sees their internal type as strings, meaning it HAS to produce an object. — Marc B, Nov 19 '13 at 21:23
@MarcB that's how i've to pass an associative array and in python, convert it to an dictionary. instead of keys like `1,2,3` i'll have `"name", "mail"` etc as keys. i guess, problem is with `escapeshellarg()` in windows. i've read some issues. — RatDon, Nov 19 '13 at 21:27
gotcha. but the shellarg stuff won't matter to python, any escaping done by the shell will only be relevant to the shell, and the escapes/quotes will be gone when the data gets into python. — Marc B, Nov 19 '13 at 21:30
@MarcB don't know what is the problem. with `shell_exec("start test.py ".json_encode(json_encode($data)));` i'm receiving in python a string `{"1":"as","2":"df","3":"gh"}` for `$data = array('1' => "as",'2' => "df",'3' => "gh");` but not being able to convert that string to a dictionary with ast.literal_eval(). it's producing errors. — RatDon, Nov 19 '13 at 21:52

score 1 · Accepted Answer · answered Nov 19 '13 at 22:15

don't know how it's working. but able to tune the program according to what i want.

php code:

<?php
$data = array('1'=>"as",'2'=>"df",'3'=>"gh");
$result=shell_exec("start test.py ".json_encode(json_encode($data)));
?>

test.py:

import sys
import json

try:
    data=sys.argv[1]
except:
    print "ERROR"

print data
dit=json.loads(data)
print dit
print dit['1']
raw_input()

and got the output as required:

{"1":"as","2":"df","3":"gh"}
{u'1': u'as', u'3': u'gh', u'2': u'df'}
as

someone having a good knowledge in these pls explain.

Yeap. Please explain. But thanks for the tips.it solved my issue. — LearningPath, Jun 17 '18 at 19:01

score 1 · Answer 2 · answered Jun 09 '16 at 11:52

The problem is the following:

On Windows, escapeshellarg() removes percent signs, replaces double quotes with spaces and adds double quotes around the string.

-> https://secure.php.net/manual/en/function.escapeshellarg.php

I'd recommend using addslashes(...)

exec("test.py " . addslashes(json_encode($json)) . " 2>&1", $output, $exit_code);

php to python inter-process communication with large data by json

2 Answers2