CODEWITHSUNDEEP
javascriptpythonajaxcgi
Nebelhom
Nebelhom

Reputation: 3911

Python/CGI/Ajax: cgi.FieldStorage does not receive arguments

I am trying to get a Python, cgi module, ajax/javascript combination to work. Due to the nature of my server access (essentially rented webspace), I cannot install things like django or any other webframework. I am stuck with cgi for now. I am able to call the python file to simply print out something, but once it comes to passing an argument to the python file the cgi.FieldStorage() does not receive any input. When I add a print statement for the FieldStorage, the output is as follows:

FieldStorage(None, None, [])

You can find all the necessary code below. Essentially, all I am trying to do (for testing purposes) is to get a string from a text input, add a "1" to the end of it and return it.

Interestingly, when I use a simple php file that does the exact same thing and use it in the otherwise exact same script, the script works without any issues. Here's a typical php script that I tried:

<?php
$user = urldecode(implode(file('php://input')));
$adj_user = $user . "1";
echo $adj_user;
?>

(Please note that I want to use python, because I am far more comfortable with it and I dislike php quite a bit.)

I have the feeling that I am just a little bit dense and it is something very simple. Any help in finding what I am doing wrong is very appreciated. Thanks a lot in advance!

P.S. I have scoured stackoverflow and the web quite some time before I posted on here. There are many related topics, but nothing quite as (seemingly) simple as what I am asking. If there is an answered duplicate to this question then I apologise and would be grateful for a link. Thanks again.

The traceback is:

Traceback (most recent call last):
  File "/home/www/xxxxx/html/cgi-bin/hello.py", line 14, in &lt;module&gt;
    adj_user = form['user'] +  "1"
  File "/usr/lib/python2.5/cgi.py", line 567, in __getitem__
    raise KeyError, key
KeyError: 'user'

Here is the "index.html"

<!DOCTYPE html>
<html>
    <head>
    <title>Report</title>
    <script type='text/javascript' src='test.js'></script>
    </head>
    <body>
    <form method="post" action=""> 

    <p>Please enter your name here:
    <input type="text" name="user">

    <input type="submit" name="submit" value="Submit" onClick="return hello(this.form.user.value);">
    </p>

    </form>
    </body>
</html>

This is the "test.js" file:

function hello(user) {
    // Mozilla version
    if (window.XMLHttpRequest) {
        xhr = new XMLHttpRequest();
    }
// IE version
    else if (window.ActiveXObject) {
        xhr = new ActiveXObject("Microsoft.XMLHTTP");
    }
    //user=encodeURIComponent(user);
    xhr.open("POST", "../cgi-bin/hello.py");
    xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded; charset=UTF-8');
    xhr.send(user);

    xhr.onreadystatechange=function() {
        if (xhr.readyState===4) {
            adj_user = xhr.responseText;
            alert ("Hello " + adj_user);
        }
    }
    return false;
}

and lastly "hello.py" in my server's cgi-bin

#!/usr/bin/env python
# -*- coding: UTF-8 -*-

import cgi
form = cgi.FieldStorage()

# enable debugging
import cgitb
cgitb.enable()

print "Content-Type: text/html;charset=utf-8"
print

adj_user = form['user'] +  "1"
print adj_user

EDIT

I made some progress, but it still isn't what I am hoping for. I changed the following block as follows:

    xhr.open("GET", "../cgi-bin/hello.py?user=" + user, true);
    xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded; charset=UTF-8');
    xhr.send();

Please note the change from POST to GET and the suffix ' "?user=" + user ', as well as the removal of the 'user' argument in the send() method.

Now this does, what I want, but it just shouldn't "be" that way. There must be a way to get this to work the classical way...

As usual, any attempt or suggestion is welcome. I really don't know what else to try. Thanks fellas.

Upvotes: 3

Views: 3049

Answers (1)

Quentin
Quentin

Reputation: 944008

The format of application/x-www-form-urlencoded data is:

key=value&key2=value2

… where the keys and values are URL encoded.

You are posting just the value of a field, with no keys.

var postData = encodeURIComponent('user') + '=' + encodeURIComponent(user);
xhr.send(postData);

The reason that the PHP code was working was because you was reading the raw POST data instead of $_POST['user'] (which is what your Python was equivalent to).

You also need to access form['user'].value rather than form['user']. That will return a str so you can't concatenate it with + 1 without performing type conversion.

Upvotes: 3

Related Questions