If our network has a proxy , then some sites can not be opened.
I want to check iteratively , how many sites can be accessed through our network.
Find out what the source code of the Proxy Block page is.
Use urllib and BeautifulSoup to try and scrape the page and parse the page's source code to see if you can find something unique that can tell you if the site is accessible or not.
For example, in my office, when a page is blocked by our proxy the title tag of the source code is <title>Network Error</title>. Something such as that could be an identifier for you.
Just a quick idea.
So for example you could have the URL's to test in a list and iterate through the list in a loop and try and scrape each site.
Python : How to check if a given site is accessible through a proxy network?