Python call from website is causing webpage to hang

I have spent a little time looking through the site, but ultimately wind up at the same place with code that stops functioning. I’m a coding novice and currently trying to learn HTML, PHP, python and SQL

I’m trying to trigger a python script from php code on a webserver. the python script and the webpage are located in the same folder on the server.

The website calls a script and is then supposed to open a new page to say the script ran.

The code I’m trying to call has a repeat function that runs every 10 seconds (this function is necessary) – this stops the webpage from loading.

This is the php. 

    if($datetime_diff < 2){
    // code as ran within datetime diff value so all good - don't show button
    echo "
    <p>SQL Time check shows python code is running</p>
    ";
    }else{
    // show link to run python code
    echo "
    <p><a href='python_call.php' class='btn btn-primary ml-3'>Run python code</a></p>
    ";
    }

this is the python call that is called in the href..

shell_exec('python pdl_test.py > error.txt 2>&1 &');
echo "
    <p><a href='admin_page.php' class='btn btn-primary ml-3'>Admin Page</a></p>
    ";

I was under the impression that the 2>&1 & should allow the php to continue without checking for a result.

the error.txt file displays complete

this is the script that the first python code is calling..

def repeat():
    print (datetime.now())
    try:
        subprocess.run(['python', 'sql_update.py'])
    except:
        print ('error')
    else:
        print ('called')
 
    print (datetime.now())
    print ("program complete")
 
    time.sleep(10)
    
while True:
    repeat()

and this is the SQL (this works OK)

cursorDestination.execute('''
            UPDATE eng_pdl_test
            SET scriptRan = getdate()
            WHERE id = 1
            ''')
cnxnDestination.commit()

 
I can see from the Task manager program that the command is being executed, and is retained.

If I close the first webpage and re-open it, the update shows as complete and, on page refresh the timer value increments every 10 seconds.

Also, if the pdl_test.py script is already running everything works correctly.

so ,in summary the code works correctly, it just doesn’t finish loading the page correctly.

Would someone please point me in a new/better/right direction please.

i’ve also tried Popen with no success.
subprocess.Popen(['python', 'sql_update.py'])

i’ve confirmed server calls are permitted using this code..
 

$output = null;
$return_var = null;
exec('echo "test"', $output, $return_var);
if ($return_var === 0) {
    echo 'command execution permitted.';
} else {
    echo 'command execution not permitted.';
}

if i call the sql_update.py script it works as expected. and I can return values if needed, but I can’t do this because I need the 10 second repeat.

exec('python sql_update.py', $output, $return_var);
echo "Output: " . implode("n", $output) . "n";
echo "Return value: " . $return_var . "n";