Sending array from PHP to Python and then parse in Python

Question

I am having a hard time parsing an array in python when the array is coming from a php file.

test.php

    $count = 3;
    $before_json = array("qwe","wer","ert");
    print_r($before_json );

    $after_json = json_encode($before_json );
    echo $after_json;

    $command = escapeshellcmd("test.py $after_json $count");
    $output = shell_exec($command);
    echo $output;

print_r($before_json ); will display - Array ( [0] => qwe [1] => wer [2] => ert )

echo $after_json; will display - ["qwe","wer","ert"]

py.test

    import sys
    after_json = sys.argv[1]
    count = sys.argv[2]
    print (device_id)

print (after_json) will print - [qwe,wer,ert]

print (after_json[1]) will print - q

How can I have it print out any of the 3 items that are in after_json?

You forgot to parse the json in Python. Import the json module, then you can use json.loads(after_json) to turn the JSON string into a list. Update: I felt this should be an answer rather than a comment, but I'll leave the comment since it already has some upvotes. — rickdenhaan
– rickdenhaan, Commented Oct 21, 2017 at 18:43
First make the python program do what you expect it do - you're just reading a string and outputting the first character from the string now .. and try to use a temporary file or pipes to send data between programs, and not the command line — MatsLindh
– MatsLindh, Commented Oct 21, 2017 at 18:44

aufziehvogel · Accepted Answer · 2017-10-21 18:56:16Z

1

The problem you are seeing is the lack of parsing of JSON in Python, as stated by rickdenhaan.

However you also want to make sure to quote your string correctly, when you send it to the shell interpreter in this line:

$command = escapeshellcmd("test.py $after_json $count");

If we manually fill in the variables, we will get the following result (not sure what $count is, so I just assumed a value of 3):

$command = escapeshellcmd("test.py [\"qwe\",\"wer\",\"ert\"] 3");

This only works, because there are no spaces in the formatting of your JSON. As soon as you have spaces in the parsed JSON, your shell call of the Python script will totally fail. It's also a security nightmare, because each of the elements of the JSON array can lead to arbitrary code execution in your shell.

You have to escape your arguments when you pass them to the shell. For this, you should use the function escapeshellarg.

This is probably what you want to do instead:

$escaped_json = escapeshellarg($after_json)
$command = escapeshellcmd("test.py $escaped_json $count");

If you are not 100% sure that $count is an integer, you should also call escapeshellarg on that parameter.

edited Oct 21, 2017 at 18:56

answered Oct 21, 2017 at 18:47

aufziehvogel

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4 Comments

Gino Over a year ago

Thanks folks. I made your changes but I am getting a blank output. $count is just a counter that I will use in the py script to loop. test.php is $count = 3; $before_json = array("qwe","wer","ert"); $after_json = json_encode($before_json ); $escaped_json = escapeshellarg($after_json); $command = escapeshellcmd("python test.py $escaped_json $count"); $output = shell_exec($command); echo $output; and test.py is import sys, json escaped_json = sys.argv[1] count = sys.argv[2] parsed_data = json.loads(escaped_json) print (parsed_data[0])

Gino Over a year ago

Also noticed that doing a simple print"test" after the line parsed_data = json.loads(escaped_json) will not print

Gino Over a year ago

If I do print escaped_json withon test.py, I get this [\"qwe\",\"wer\",\"ert\"]

Gino Over a year ago

I got it all working by writing to a file, stripping the [ and ] and then parsing the info. Thanks for everyones input

rickdenhaan · Accepted Answer · 2017-10-21 18:46:31Z

0

You still need to parse the JSON string in Python. You can use the json module for that:

import sys, json
after_json = sys.argv[1]
count = sys.argv[2]

parsed_data = json.loads(after_json)
print (parsed_data[0])  # will print "qwe"

answered Oct 21, 2017 at 18:46

rickdenhaan

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Comments

Kasra · Accepted Answer · 2019-10-25 12:51:52Z

0

after_json=after_json[1:-1].split(",")

while after_json is ["qwe","wer","ert"] u can omit first and last character and then split remaining string wich can be split by comma

edited Oct 25, 2019 at 12:51

answered Oct 21, 2019 at 6:54

Kasra

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1 Comment

BDL Over a year ago

Although the code might solve the problem, a good answer should also explain what the problem is and how the code helps.

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