How extract all URLs in a website using BeautifulSoup

I'm working on a project that require to extract all links from a website, with using this code I'll get all of links from single URL:

import requests
from bs4 import BeautifulSoup, SoupStrainer

source_code = requests.get('https://stackoverflow.com/')
soup = BeautifulSoup(source_code.content, 'lxml')
links = []

for link in soup.find_all('a'):
    links.append(str(link))

problem is that if I want to extract all URLs, I have to write another for loop and then another one ... . I want to extract all URLs that are exist in this website and in this website's sub domains. is there any way to do this without writing nested for? and even with writing nested for, I don't know how many for should I use to get all URLs.

WoW, it takes about 30 min to find a solution, I found a simple and efficient way to do this, As @αԋɱҽԃ-αмєяιcαη mentioned, some time if your website linked to a BIG website like google, etc, it wont be stop until you memory get full of data. so there are steps that you should consider.

1. make a while loop to seek thorough your website to extract all of urls
2. use Exceptions handling to prevent crashes
3. remove duplicates and separate the urls
4. set a limitation to number of urls, like when 1000 urls found
5. stop while loop to prevent your PC's memory getting full

here a sample code and it should works fine, I actually tested it and it was fun fore me:

import requests
from bs4 import BeautifulSoup
import re
import time

source_code = requests.get('https://stackoverflow.com/')
soup = BeautifulSoup(source_code.content, 'lxml')
data = []
links = []


def remove_duplicates(l): # remove duplicates and unURL string
    for item in l:
        match = re.search("(?P<url>https?://[^\s]+)", item)
        if match is not None:
            links.append((match.group("url")))


for link in soup.find_all('a', href=True):
    data.append(str(link.get('href')))
flag = True
remove_duplicates(data)
while flag:
    try:
        for link in links:
            for j in soup.find_all('a', href=True):
                temp = []
                source_code = requests.get(link)
                soup = BeautifulSoup(source_code.content, 'lxml')
                temp.append(str(j.get('href')))
                remove_duplicates(temp)
                
                if len(links) > 162: # set limitation to number of URLs
                    break
            if len(links) > 162:
                break
        if len(links) > 162:
            break
    except Exception as e:
        print(e)
        if len(links) > 162:
            break

for url in links:
    print(url)

and the output will be:

https://stackoverflow.com
https://www.stackoverflowbusiness.com/talent
https://www.stackoverflowbusiness.com/advertising
https://stackoverflow.com/users/login?ssrc=head&returnurl=https%3a%2f%2fstackoverflow.com%2f
https://stackoverflow.com/users/signup?ssrc=head&returnurl=%2fusers%2fstory%2fcurrent
https://stackoverflow.com
https://stackoverflow.com
https://stackoverflow.com/help
https://chat.stackoverflow.com
https://meta.stackoverflow.com
https://stackoverflow.com/users/signup?ssrc=site_switcher&returnurl=%2fusers%2fstory%2fcurrent
https://stackoverflow.com/users/login?ssrc=site_switcher&returnurl=https%3a%2f%2fstackoverflow.com%2f
https://stackexchange.com/sites
https://stackoverflow.blog
https://stackoverflow.com/legal/cookie-policy
https://stackoverflow.com/legal/privacy-policy
https://stackoverflow.com/legal/terms-of-service/public
https://stackoverflow.com/teams
https://stackoverflow.com/teams
https://www.stackoverflowbusiness.com/talent
https://www.stackoverflowbusiness.com/advertising
https://www.g2.com/products/stack-overflow-for-teams/
https://www.g2.com/products/stack-overflow-for-teams/
https://www.fastcompany.com/most-innovative-companies/2019/sectors/enterprise
https://www.stackoverflowbusiness.com/talent
https://www.stackoverflowbusiness.com/advertising
https://stackoverflow.com/questions/55884514/what-is-the-incentive-for-curl-to-release-the-library-for-free/55885729#55885729
https://insights.stackoverflow.com/
https://stackoverflow.com
https://stackoverflow.com
https://stackoverflow.com/jobs
https://stackoverflow.com/jobs/directory/developer-jobs
https://stackoverflow.com/jobs/salary
https://www.stackoverflowbusiness.com
https://stackoverflow.com/teams
https://www.stackoverflowbusiness.com/talent
https://www.stackoverflowbusiness.com/advertising
https://stackoverflow.com/enterprise
https://stackoverflow.com/company/about
https://stackoverflow.com/company/about
https://stackoverflow.com/company/press
https://stackoverflow.com/company/work-here
https://stackoverflow.com/legal
https://stackoverflow.com/legal/privacy-policy
https://stackoverflow.com/company/contact
https://stackexchange.com
https://stackoverflow.com
https://serverfault.com
https://superuser.com
https://webapps.stackexchange.com
https://askubuntu.com
https://webmasters.stackexchange.com
https://gamedev.stackexchange.com
https://tex.stackexchange.com
https://softwareengineering.stackexchange.com
https://unix.stackexchange.com
https://apple.stackexchange.com
https://wordpress.stackexchange.com
https://gis.stackexchange.com
https://electronics.stackexchange.com
https://android.stackexchange.com
https://security.stackexchange.com
https://dba.stackexchange.com
https://drupal.stackexchange.com
https://sharepoint.stackexchange.com
https://ux.stackexchange.com
https://mathematica.stackexchange.com
https://salesforce.stackexchange.com
https://expressionengine.stackexchange.com
https://pt.stackoverflow.com
https://blender.stackexchange.com
https://networkengineering.stackexchange.com
https://crypto.stackexchange.com
https://codereview.stackexchange.com
https://magento.stackexchange.com
https://softwarerecs.stackexchange.com
https://dsp.stackexchange.com
https://emacs.stackexchange.com
https://raspberrypi.stackexchange.com
https://ru.stackoverflow.com
https://codegolf.stackexchange.com
https://es.stackoverflow.com
https://ethereum.stackexchange.com
https://datascience.stackexchange.com
https://arduino.stackexchange.com
https://bitcoin.stackexchange.com
https://sqa.stackexchange.com
https://sound.stackexchange.com
https://windowsphone.stackexchange.com
https://stackexchange.com/sites#technology
https://photo.stackexchange.com
https://scifi.stackexchange.com
https://graphicdesign.stackexchange.com
https://movies.stackexchange.com
https://music.stackexchange.com
https://worldbuilding.stackexchange.com
https://video.stackexchange.com
https://cooking.stackexchange.com
https://diy.stackexchange.com
https://money.stackexchange.com
https://academia.stackexchange.com
https://law.stackexchange.com
https://fitness.stackexchange.com
https://gardening.stackexchange.com
https://parenting.stackexchange.com
https://stackexchange.com/sites#lifearts
https://english.stackexchange.com
https://skeptics.stackexchange.com
https://judaism.stackexchange.com
https://travel.stackexchange.com
https://christianity.stackexchange.com
https://ell.stackexchange.com
https://japanese.stackexchange.com
https://chinese.stackexchange.com
https://french.stackexchange.com
https://german.stackexchange.com
https://hermeneutics.stackexchange.com
https://history.stackexchange.com
https://spanish.stackexchange.com
https://islam.stackexchange.com
https://rus.stackexchange.com
https://russian.stackexchange.com
https://gaming.stackexchange.com
https://bicycles.stackexchange.com
https://rpg.stackexchange.com
https://anime.stackexchange.com
https://puzzling.stackexchange.com
https://mechanics.stackexchange.com
https://boardgames.stackexchange.com
https://bricks.stackexchange.com
https://homebrew.stackexchange.com
https://martialarts.stackexchange.com
https://outdoors.stackexchange.com
https://poker.stackexchange.com
https://chess.stackexchange.com
https://sports.stackexchange.com
https://stackexchange.com/sites#culturerecreation
https://mathoverflow.net
https://math.stackexchange.com
https://stats.stackexchange.com
https://cstheory.stackexchange.com
https://physics.stackexchange.com
https://chemistry.stackexchange.com
https://biology.stackexchange.com
https://cs.stackexchange.com
https://philosophy.stackexchange.com
https://linguistics.stackexchange.com
https://psychology.stackexchange.com
https://scicomp.stackexchange.com
https://stackexchange.com/sites#science
https://meta.stackexchange.com
https://stackapps.com
https://api.stackexchange.com
https://data.stackexchange.com
https://stackoverflow.blog?blb=1
https://www.facebook.com/officialstackoverflow/
https://twitter.com/stackoverflow
https://linkedin.com/company/stack-overflow
https://creativecommons.org/licenses/by-sa/4.0/
https://stackoverflow.blog/2009/06/25/attribution-required/
https://stackoverflow.com
https://www.stackoverflowbusiness.com/talent
https://www.stackoverflowbusiness.com/advertising

Process finished with exit code 0

I set the limitation to 162, you can increase it as many as you want and you ram allowed.