How can I check if a URL exists with Django’s vali

Question

I want to check in django if a URL exists and if it does I want to show something on screen, i.e.:

if URL_THAT_POINTS_TO_SOME_PDF exists 
     SHOW_SOMETHING

Answer 1

from django.core.validators import URLValidator
from django.core.exceptions import ValidationError

validate = URLValidator(verify_exists=True)    
value = request.GET.get('url', None)

if value:        
    try:
        validate(value)
    except ValidationError, e:
        print e

validate(value) fails if the url is not preceeded with a schema like http://. I wonder if that is by design.

Answer 2

Problem

from django.core.validators import URLValidator says that www.google.ro is invalid. Which is wrong in my point of view. Or at least not enough.

How to solve it?

The clue Is to look at the source code for models.URLField, you will see that it uses forms.FormField as a validator. Which does more than URLValidator from above

Solution

If I want to validate a url like http://www.google.com or like www.google.ro, I would do the following:

from django.forms import URLField

def validate_url(url):
    url_form_field = URLField()
    try:
        url = url_form_field.clean(url)
    except ValidationError:
        return False
    return True

I found this useful. Maybe it helps someone else.

Answer 3

It took an additional:

from django.core.exceptions import ValidationError

for it to work for me. Just saying ;0)

Answer 4

I have not seen the answer here. It might helpful to someone else.

from django import forms
f = forms.URLField()
try:
    f.clean(http://example.com)
    print "valid url"
except:
    print "invalid url"

Answer 5

Edit: Please note, this is no longer valid for any version of Django above 1.5

I assume you want to check if the file actually exists, not if there is just an object (which is just a simple if statement)

First, I will recommend always looking through Django's source code because you will find some great code that you could use :)

I assume you want to do this within a template. There is no built-in template tag to validate a URL but you could essentially use that URLValidator class within a template tag to test it. Simply:

from django.core.validators import URLValidator
from django.core.exceptions import ValidationError

validate = URLValidator(verify_exists=True)
try:
    validate('http://www.somelink.com/to/my.pdf')
except ValidationError, e:
    print e

The URLValidator class will spit out the ValidationError when it can't open the link. It uses urllib2 to actually open the request so it's not just using basic regex checking (But it also does that.)

You can plop this into a custom template tag, which you will find out how to create in the django docs and off you go.

Hope that is a start for you.

Answer 6

See: http://www.agmweb.ca/2009-04-19-django-urlpatterns---its-more-than-just-urls/

In django 1.10 i now use:

from django.core.urlresolvers import RegexURLResolver, Resolver404

if 'next' in request.GET.keys():
    n = request.GET["next"].strip('/') + "/"
    resolver = RegexURLResolver(r'', urls)
    try:
        callback, callback_args, callback_kwargs = resolver.resolve(n)
        return HttpResponseRedirect(str(request.GET["next"]))
    except Resolver404:
        raise PermissionDenied("This page is not available")