How can I prepend http to a url if it doesn't begin with http?

Question

I have urls formatted as:

google.com
www.google.com
http://google.com
http://www.google.com

I would like to convert all type of links to a

Answer 1

For the formats that you mention in your question, you can do something as simple as:

def convert(url):
    if url.startswith('http://www.'):
        return 'http://' + url[len('http://www.'):]
    if url.startswith('www.'):
        return 'http://' + url[len('www.'):]
    if not url.startswith('http://'):
        return 'http://' + url
    return url

But please note that there are probably other formats that you are not anticipating. In addition, keep in mind that the output URL (according to your definitions) will not necessarily be a valid one (i.e., the DNS will not be able to translate it into a valid IP address).