Can urlopen be blocked by websites?

[snippsat]

Use Requests and not urllib,also a User agent that site use.

import requests
from bs4 import BeautifulSoup

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.89 Safari/537.36'
}

url = 'https://www.nseindia.com/option-chain'
response = requests.get(url, headers=headers)
soup = BeautifulSoup(response.content, 'lxml')
print(soup.find('title').text)

Output:
NSE - Option Chain

I guess you can parse anything on this site,turn off JavaScripts in browser then reload.
What you see now is what you get with Requests/BS.
This is common problem that Selenium solve.
There are many Threads about this here if search,one with a other stock site.