Simple random file CAPTCHA
This is a snippet for a simple CAPTCHA. A random image from a list of images is shown, and the form checks if the correct solution was given. Normally I would use django-simple-captcha or maybe reCAPTCHA, but in this case I wanted to have a number of fixed images, nothing dynamically generated. I wanted to include the contact form in multiple pages, most of which are `direct_to_template` generic views. However, passing the random image to the `extra_context` of `direct_to_template` didn't work, because the value was only initialized once on startup. Therefore I pass the list of possible choices to `extra_context`, and use the template filter `|random` to select one image. The form's clean method will check if the correct solution was given when `form.is_valid()` is called in the view. If not, the view will display a new captcha. Of course there are other, more elegant solutions like a custom template tag or overriding the generic view, but this works fine for me. Using a fixed number of images will probably not provide good protection for sites that are of much interest to spammers, but for smaller sites it should be sufficient. You can see the CAPTCHA in action at [http://www.lackieren-in-polen.de/](http://www.lackieren-in-polen.de/)
- captcha
- random