My answer to my interview question. Create an object to store IP ranges as a blacklist and return if an IP is in the blacklist. Assume no range overlap.

interview_answer.py

def ip2int(ip):
    o = map(int, ip.split('.'))
    res = (16777216 * o[0]) + (65536 * o[1]) + (256 * o[2]) + o[3]
    return "{:0>32b}".format(res)
    
class BlacklistNode(object):
    def __init__(self, parent=None):
        self.parent = parent
        self.branches = {}
        self.blocked = False
        
    
class IPBlacklist(object):
    def __init__(self):
        self.root = BlacklistNode()
        
    def get_last(self, ip_str, create=False):
        curr = self.root
        
        for b in ip_str:
            if b not in curr.branches:
                if create:
                    curr.branches[b] = BlacklistNode(parent=curr)
                else:
                    return curr
            curr = curr.branches[b]
        
        return curr
        
    def put(self, ip, subnet=32):
        bin_ip = ip2int(ip)[:subnet]
        last = self.get_last(bin_ip, True)
        last.blocked = True
        return last
        
    def get(self, ip):
        bin_ip = ip2int(ip)
        last = self.get_last(bin_ip)
        return last.blocked
        
bl = IPBlacklist()

bl.put('10.11.2.0', 24)
bl.put('10.11.3.0', 24)

print bl.get('10.11.2.5') #T
print bl.get('10.11.4.5') #F
print bl.get('10.11.3.5') #T
print bl.get('10.11.3.10') #T
print bl.get('10.12.2.5') #F