check if a URL to an image is up and exists in Python

This is the best approach working for my application, based also on previous comments:

import requests

def is_url_image(image_url):
   image_formats = ("image/png", "image/jpeg", "image/jpg")
   r = requests.head(image_url)
   if r.headers["content-type"] in image_formats:
      return True
   return False

This is one way that is quick:

It doesn't really verify that is really an image file, it just guesses based on file extention and then checks that the url exists. If you really need to verify that the data returned from the url is actually an image (for security reasons) then this solution would not work.

import mimetypes, urllib2

def is_url_image(url):    
    mimetype,encoding = mimetypes.guess_type(url)
    return (mimetype and mimetype.startswith('image'))

def check_url(url):
    """Returns True if the url returns a response code between 200-300,
       otherwise return False.
    """
    try:
        headers = {
            "Range": "bytes=0-10",
            "User-Agent": "MyTestAgent",
            "Accept": "*/*"
        }

        req = urllib2.Request(url, headers=headers)
        response = urllib2.urlopen(req)
        return response.code in range(200, 209)
    except Exception:
        return False

def is_image_and_ready(url):
    return is_url_image(url) and check_url(url)

You can read the header of the http request, it contains some meta-data like the content-type.

On python 3:

from urllib.request import urlopen
image_formats = ("image/png", "image/jpeg", "image/gif")
url = "http://localhost/img.png"
site = urlopen(url)
meta = site.info()  # get header of the http request
if meta["content-type"] in image_formats:  # check if the content-type is a image
    print("it is an image")

You can also get other info like the size of the image and etc. The good news about this is that it doesn't download the image. It could fail if the header says that it is an image and it is not, but you can still do a last check and download the image if it pass the first filter.

Take a look into imghdr

Here is some example code:

import imghdr
import httplib
import cStringIO

conn = httplib.HTTPConnection('www.ovguide.com', timeout=60)
path = '/img/global/ovg_logo.png'
conn.request('GET', path)
r1 = conn.getresponse()

image_file_obj = cStringIO.StringIO(r1.read())
what_type = imghdr.what(image_file_obj)

print what_type

This should return 'png'. If it is not an image it will return None

Hope that helps!

-Blake