Parsing Python array in PHP

Question

I have a Python script running on my server that creates a 2D list like so:

[['Header1', 'Header2', 'Header3'], ['2012-09-10 00:11:00', '61.3', '57.0'], ...]

I pass this back to the PHP script which is running my webpage. Here's the PHP I'm currently using to get the array. I get the rows, but obviously with an unwanted [[ at the start and ]] at the end.

exec("python weatherdata.py $stationID $startdate $enddate", $pyoutput);
$vars = explode("], [", $pyoutput[0]);

For the sake of explaining what I actually want to do, since there's bound to be a "proper" solution (I'm not at all familiar with PHP), what I want to do is adapt the code from here which download a CSV file to the user, but uses mySQL to populate it. The set-up part here works fine.

Edited in response to Jack's answer below

// Commented out my working parsing part
// remove the start and end square braces then split into rows
//$output = str_replace("[[","",$pyoutput);
//$output = str_replace("]]","",$output);
//$rows = explode("], [", $output[0]);

// output headers so that the file is downloaded rather than displayed
header('Content-Type: text/csv; charset=utf-8');
header('Content-Disposition: attachment; filename='data.csv');

// create a file pointer connected to the output stream
$output = fopen('php://output', 'w');

foreach (preg_split('/],\s*\[/', trim($pyoutput, '[]')) as $row) {
        $data= preg_split("/',\s*'/", trim($row, "'"));
        fputcsv($data);
}
// Commented out my working write to CSV part
// write rows
//foreach ($rows as $row){
//    $row = str_replace("'","",$row);
//    $row = explode(",", $row);
//    fputcsv($output, $row);
//}

If you can have Python output the array with double quotes instead of single quotes, you can just json_decode() it without modification. Try and use an interoperable standard for this, JSON seems ideally suited. — DaveRandom
– DaveRandom, Commented Dec 14, 2012 at 13:31
This seems like the right way to go. I'll see if it's possible - although could it also be done as a string replace at the PHP end? — Jamie Bull
– Jamie Bull, Commented Dec 14, 2012 at 13:54
I'll answer that myself - yes it can $output = str_replace("'",'"',$output); — Jamie Bull
– Jamie Bull, Commented Dec 14, 2012 at 13:57
That is not a safe option. Consider ['Some string with a \' quote in it'] - the data will be modified. Does Python not have a json encoding function? — DaveRandom
– DaveRandom, Commented Dec 14, 2012 at 14:03

Ja͢ck · Accepted Answer · 2012-12-14 13:57:26Z

4

Not sure whether this is viable for you, but since PHP 5.4 it supports the short array syntax, e.g. [1, 2, 3] instead of array(1, 2, 3).

So, you could just use evil ... I mean eval():

$vars = eval(`python weatherdata.py $stationID $startdate $enddate`);

Otherwise, if the array syntax is always in that format, just break it apart with preg_split(), first on square brackets and then on single quotes:

foreach (preg_split('/],\s*\[/', trim($s, '[]')) as $row) {
        $data = preg_split("/',\s*'/", trim($row, "'"));
        print_r($data);
}

Output:

Array
(
    [0] => Header1
    [1] => Header2
    [2] => Header3
)
Array
(
    [0] => 2012-09-10 00:11:00
    [1] => 61.3
    [2] => 57.0
)

edited Dec 14, 2012 at 13:57

answered Dec 14, 2012 at 13:39

Ja͢ck

174k39 gold badges269 silver badges316 bronze badges

Sign up to request clarification or add additional context in comments.

10 Comments

Jamie Bull Over a year ago

Thanks but that's giving me an internal server error, I assume because not the right version of PHP.

Ja͢ck Over a year ago

@jamiebull updated it, assuming the strings will be "simple" :)

Jamie Bull Over a year ago

Thanks. I've cracked it now though. I would have used @Dave Random's json approach but it turns out my host doesn't include json as part of the pre-installed packages - which took hours of pointless going in circles to figure out. In the end I went with remove "[[", remove "]]", explode on "], [", foreach row, write each row, parsing it as you go along. Hacky as can be but it's working.

Ja͢ck Over a year ago

@JamieBull isn't that basically the second part of my answer? :)

Jamie Bull Over a year ago

It may well be. As I said, PHP's new to me (like, yesterday new). I'd actually missed the second part to your answer. I just had a quick go at implementing it your way and I'm sure the problem's at my end. Should I be passing in my $output as the $s variable in your snippet then writing to the CSV with fputcsv($data); beacause that's outputting a blank CSV?

|

Collectives™ on Stack Overflow

Parsing Python array in PHP

1 Answer 1

10 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

10 Comments

Your Answer

Sign up or log in

Post as a guest

Related