Check if the url link is correct

问题:

I want to open many url's (I open one url, search for all links on this webstie and open also them or download images etc. from this inks). So first I wanted to check if the url is correct, so I used an if statement:

if not urlparse.urlparse(link).netloc:
 return 'broken url'

But I noticed that some values did not pass this statement. I came across a website when a links looked like: //b.thumbs.redditmedia.com/7pTYj4rOii6CkkEC.jpg, but I had an error: ValueError: unknown url type: //b.thumbs.redditmedia.com/7pTYj4rOii6CkkEC.jpg, but my if statement didn't catch that. How can I check more precisely if an url works good?

回答1:

If you aren't specific about the library being used, you could do the following :

import urllib2
import re

def is_fully_alive(url, live_check = False):
    try:
        if not urllib2.urlparse.urlparse(url).netloc:
            return False

        website = urllib2.urlopen(url)
        html = website.read()

        if website.code != 200 :
            return False

        # Get all the links
        for link in re.findall('"((http|ftp)s?://.*?)"', html):
            url = link[0]

            if not urllib2.urlparse.urlparse(url).netloc:
                return False

            if live_check:
                website = urllib2.urlopen(url)

                if website.code != 200:
                    print "Failed link : ", url
                    return False

    except Exception, e:
        print "Errored while attempting to validate link : ", url
        print e
        return False

    return True

Check your url's:

>>> is_fully_alive("http://www.google.com")
True

Check by opening every single link:

# Takes some time depending on your net speed and no. of links in the page
>>> is_fully_alive("http://www.google.com", True) 
True

Check an invalid url:

>>> is_fully_alive("//www.google.com")
Errored while attempting to validate link :  //www.google.com
unknown url type: //www.google.com
False

回答2:

Pretty simple:

import urllib2

def valid_url(url):
    try:
        urllib2.urlopen(url)
        return True
    except Exception, e:
        return False

print valid_url('//b.thumbs.redditmedia.com/7pTYj4rOii6CkkEC.jpg') # False
print valid_url('http://stackoverflow.com/questions/25069947/check-if-the-url-link-is-correct') # True

You can also read the whole document by

urllib2.urlopen(url).read()

Generally if you want to download all images from an HTML document, you can do something like this:

for link, img in re.findall('http.?:\/\/b\.thumbs\.redditmedia\.com\/(\w+?\.(?:jpg|png|gif))', load(url)):
    if not os.path.exists(img):
        with open(img, 'w') as f:
            f.write(link)