如何使用Python脚本从文件中读取N条记录，其中N是PHP页面中的用户输入？

This is the PHP-code which takes user input for the number of songs to be retrieved.

  <?php
   if( isset($_GET['submit']) )
   {

    $val = htmlentities($_GET['val']);
    $tmp = shell_exec("python /opt/lampp/htdocs/dashboard/IR/song.py .$val    ");
    echo $tmp;
   }
  ?>

    <h1 class="register-title">Songs by User-ID</h1>
    <form class="register" action = "" method="get">

 <input type="text" class="register-input" id="val" placeholder="No of Songs">
    <input type="submit" name="submit" value="Retrieve" class="Retrieve-button">
   </form>

This is the python code which takes the argument from php file and executes the script. Python ex.py file

import sys
result = sys.argv[1]
N=result
f=open("song.txt")
for i in range(N):
   line=f.next().strip()   
   print line
f.close()