import urllib.request
import urllib.parse
import re

def naslovi(base):
    """Naloži stran na danem naslovu in vrni seznam naslovov, ki se pojavljajo na tej strani."""
    with urllib.request.urlopen(base) as response:
        vsebina = str(response.read())
        naslovi = re.findall(r'<a href="(http[^"]+)">', vsebina)
        return { urllib.parse.urljoin(base, url) for url in naslovi }

def pajek(base, depth):
    res = set()
    obdelava = {base}
    for i in range(depth):
        s = set()
        for url in obdelava:
            s = s.union(naslovi(url))
        res |= obdelava
        obdelava = s
    return res

print(pajek("http://www.andrej.com/", 3))