How do I pass a url and uncheck a checkbox in a post request.

The HTML looks like this:

```
<input type="checkbox" name="encodeURL" ID="encodeURL" checked="checked">

```

I am using [requests](http://docs.python-requests.org/en/latest/user/quickstart/#passing-parameters-in-urls), a 3rd party python library, like so:

```
payload = {'u': 'http://www.google.com', 'encodeURL': '0'}
r = requests.post('http://www.website.com/', data=payload)

```

So far setting 'encodeURL' to '0', 'unchecked', '' and 0 is NOT posting the request with the checkbox unchecked.
How do I find what value to pass to 'encodeURL' in order to uncheck the checkbox?