I don’t know of anything in the standard library, but PySubnetTree is a Python library that will do subnet matching.

I like to use netaddr for that:

from netaddr import CIDR, IP

if IP("192.168.0.1") in CIDR("192.168.0.0/24"):
    print "Yay!"

As arno_v pointed out in the comments, new version of netaddr does it like this:

from netaddr import IPNetwork, IPAddress
if IPAddress("192.168.0.1") in IPNetwork("192.168.0.0/24"):
    print "Yay!"

Using ipaddress (in the stdlib since 3.3, at PyPi for 2.6/2.7):

>>> import ipaddress
>>> ipaddress.ip_address('192.168.0.1') in ipaddress.ip_network('192.168.0.0/24')
True

If you want to evaluate a lot of IP addresses this way, you’ll probably want to calculate the netmask upfront, like

n = ipaddress.ip_network('192.0.0.0/16')
netw = int(n.network_address)
mask = int(n.netmask)

Then, for each address, calculate the binary representation with one of

a = int(ipaddress.ip_address('192.0.43.10'))
a = struct.unpack('!I', socket.inet_pton(socket.AF_INET, '192.0.43.10'))[0]
a = struct.unpack('!I', socket.inet_aton('192.0.43.10'))[0]  # IPv4 only

Finally, you can simply check:

in_network = (a & mask) == netw

Thank you for your script!
I have work quite a long on it to make everything working… So I’m sharing it here

• Using netaddr Class is 10 times slower than using binary conversion, so if you’d like to use it on a big list of IP, you should consider not using netaddr class

• makeMask function is not working! Only working for /8,/16,/24
  Ex:

  bits = “21” ; socket.inet_ntoa(struct.pack(‘=L’,(2L << int(bits)-1) – 1))
  ‘255.255.31.0’ whereas it should be 255.255.248.0

  So I have used another function calcDottedNetmask(mask) from http://code.activestate.com/recipes/576483-convert-subnetmask-from-cidr-notation-to-dotdecima/
  Ex:

#!/usr/bin/python
>>> calcDottedNetmask(21)
>>> '255.255.248.0'

• Another problem is the process of matching if an IP belongs to a network! Basic Operation should be to compare (ipaddr & netmask) and (network & netmask).
  Ex: for the time being, the function is wrong

#!/usr/bin/python
>>> addressInNetwork('188.104.8.64','172.16.0.0/12')
>>>True which is completely WRONG!!

So my new addressInNetwork function looks-like:

#!/usr/bin/python
import socket,struct
def addressInNetwork(ip,net):
    '''This function allows you to check if on IP belogs to a Network'''
    ipaddr = struct.unpack('=L',socket.inet_aton(ip))[0]
    netaddr,bits = net.split('/')
    netmask = struct.unpack('=L',socket.inet_aton(calcDottedNetmask(bits)))[0]
    network = struct.unpack('=L',socket.inet_aton(netaddr))[0] & netmask
    return (ipaddr & netmask) == (network & netmask)

def calcDottedNetmask(mask):
    bits = 0
    for i in xrange(32-int(mask),32):
        bits |= (1 > 24, (bits & 0xff0000) >> 16, (bits & 0xff00) >> 8 , (bits & 0xff))

And now, answer is right!!

#!/usr/bin/python
>>> addressInNetwork('188.104.8.64','172.16.0.0/12')
False

I hope that it will help other people, saving time for them!

This code is working for me on Linux x86. I haven’t really given any thought to endianess issues, but I have tested it against the “ipaddr” module using over 200K IP addresses tested against 8 different network strings, and the results of ipaddr are the same as this code.

def addressInNetwork(ip, net):
   import socket,struct
   ipaddr = int(''.join([ '%02x' % int(x) for x in ip.split('.') ]), 16)
   netstr, bits = net.split('/')
   netaddr = int(''.join([ '%02x' % int(x) for x in netstr.split('.') ]), 16)
   mask = (0xffffffff << (32 - int(bits))) & 0xffffffff
   return (ipaddr & mask) == (netaddr & mask)

Example:

>>> print addressInNetwork('10.9.8.7', '10.9.1.0/16')
True
>>> print addressInNetwork('10.9.8.7', '10.9.1.0/24')
False

Marc’s code is nearly correct. A complete version of the code is –

def addressInNetwork3(ip,net):
    '''This function allows you to check if on IP belogs to a Network'''
    ipaddr = struct.unpack('=L',socket.inet_aton(ip))[0]
    netaddr,bits = net.split('/')
    netmask = struct.unpack('=L',socket.inet_aton(calcDottedNetmask(int(bits))))[0]
    network = struct.unpack('=L',socket.inet_aton(netaddr))[0] & netmask
    return (ipaddr & netmask) == (network & netmask)

def calcDottedNetmask(mask):
    bits = 0
    for i in xrange(32-mask,32):
        bits |= (1 << i)
    return "%d.%d.%d.%d" % ((bits & 0xff000000) >> 24, (bits & 0xff0000) >> 16, (bits & 0xff00) >> 8 , (bits & 0xff))

Obviously from the same sources as above…

A very Important note is that the first code has a small glitch – The IP address 255.255.255.255 also shows up as a Valid IP for any subnet. I had a heck of time getting this code to work and thanks to Marc for the correct answer.

from netaddr import all_matching_cidrs

>>> from netaddr import all_matching_cidrs
>>> all_matching_cidrs("212.11.70.34", ["192.168.0.0/24","212.11.64.0/19"] )
[IPNetwork('212.11.64.0/19')]

Here is the usage for this method:

>>> help(all_matching_cidrs)

Help on function all_matching_cidrs in module netaddr.ip:

all_matching_cidrs(ip, cidrs)
    Matches an IP address or subnet against a given sequence of IP addresses and subnets.

    @param ip: a single IP address or subnet.

    @param cidrs: a sequence of IP addresses and/or subnets.

    @return: all matching IPAddress and/or IPNetwork objects from the provided
    sequence, an empty list if there was no match.

Basically you provide an ip address as the first argument and a list of cidrs as the second argument. A list of hits are returned.

#This works properly without the weird byte by byte handling
def addressInNetwork(ip,net):
    '''Is an address in a network'''
    # Convert addresses to host order, so shifts actually make sense
    ip = struct.unpack('>L',socket.inet_aton(ip))[0]
    netaddr,bits = net.split('/')
    netaddr = struct.unpack('>L',socket.inet_aton(netaddr))[0]
    # Must shift left an all ones value, /32 = zero shift, /0 = 32 shift left
    netmask = (0xffffffff << (32-int(bits))) & 0xffffffff
    # There's no need to mask the network address, as long as its a proper network address
    return (ip & netmask) == netaddr 

I tried Dave Webb’s solution but hit some problems:

Most fundamentally – a match should be checked by ANDing the IP address with the mask, then checking the result matched the Network address exactly. Not ANDing the IP address with the Network address as was done.

I also noticed that just ignoring the Endian behaviour assuming that consistency will save you will only work for masks on octet boundaries (/24, /16). In order to get other masks (/23, /21) working correctly I added a “greater than” to the struct commands and changed the code for creating the binary mask to start with all “1” and shift left by (32-mask).

Finally, I added a simple check that the network address is valid for the mask and just print a warning if it is not.

Here’s the result:

def addressInNetwork(ip,net):
    "Is an address in a network"
    ipaddr = struct.unpack('>L',socket.inet_aton(ip))[0]
    netaddr,bits = net.split('/')
    netmask = struct.unpack('>L',socket.inet_aton(netaddr))[0]
    ipaddr_masked = ipaddr & (4294967295<<(32-int(bits)))   # Logical AND of IP address and mask will equal the network address if it matches
    if netmask == netmask & (4294967295<<(32-int(bits))):   # Validate network address is valid for mask
            return ipaddr_masked == netmask
    else:
            print "***WARNING*** Network",netaddr,"not valid with mask /"+bits
            return ipaddr_masked == netmask

Relating to all of the above, I think socket.inet_aton() returns bytes in network order, so the correct way to unpack them is probably

struct.unpack('!L', ... )

Here is a class I wrote for longest prefix matching:

#!/usr/bin/env python

class Node:
def __init__(self):
    self.left_child = None
    self.right_child = None
    self.data = "-"

def setData(self, data): self.data = data
def setLeft(self, pointer): self.left_child = pointer
def setRight(self, pointer): self.right_child = pointer
def getData(self): return self.data
def getLeft(self): return self.left_child
def getRight(self): return self.right_child

def __str__(self):
        return "LC: %s RC: %s data: %s" % (self.left_child, self.right_child, self.data)


class LPMTrie:      

def __init__(self):
    self.nodes = [Node()]
    self.curr_node_ind = 0

def addPrefix(self, prefix):
    self.curr_node_ind = 0
    prefix_bits = ''.join([bin(int(x)+256)[3:] for x in prefix.split('/')[0].split('.')])
    prefix_length = int(prefix.split('/')[1])
    for i in xrange(0, prefix_length):
        if (prefix_bits[i] == '1'):
            if (self.nodes[self.curr_node_ind].getRight()):
                self.curr_node_ind = self.nodes[self.curr_node_ind].getRight()
            else:
                tmp = Node()
                self.nodes[self.curr_node_ind].setRight(len(self.nodes))
                tmp.setData(self.nodes[self.curr_node_ind].getData());
                self.curr_node_ind = len(self.nodes)
                self.nodes.append(tmp)
        else:
            if (self.nodes[self.curr_node_ind].getLeft()):
                self.curr_node_ind = self.nodes[self.curr_node_ind].getLeft()
            else:
                tmp = Node()
                self.nodes[self.curr_node_ind].setLeft(len(self.nodes))
                tmp.setData(self.nodes[self.curr_node_ind].getData());
                self.curr_node_ind = len(self.nodes)
                self.nodes.append(tmp)

        if i == prefix_length - 1 :
            self.nodes[self.curr_node_ind].setData(prefix)

def searchPrefix(self, ip):
    self.curr_node_ind = 0
    ip_bits = ''.join([bin(int(x)+256)[3:] for x in ip.split('.')])
    for i in xrange(0, 32):
        if (ip_bits[i] == '1'):
            if (self.nodes[self.curr_node_ind].getRight()):
                self.curr_node_ind = self.nodes[self.curr_node_ind].getRight()
            else:
                return self.nodes[self.curr_node_ind].getData()
        else:
            if (self.nodes[self.curr_node_ind].getLeft()):
                self.curr_node_ind = self.nodes[self.curr_node_ind].getLeft()
            else:
                return self.nodes[self.curr_node_ind].getData()

    return None

def triePrint(self):
    n = 1
    for i in self.nodes:
        print n, ':'
        print i
        n += 1

And here is a test program:

n=LPMTrie()
n.addPrefix('10.25.63.0/24')
n.addPrefix('10.25.63.0/16')
n.addPrefix('100.25.63.2/8')
n.addPrefix('100.25.0.3/16')
print n.searchPrefix('10.25.63.152')
print n.searchPrefix('100.25.63.200')
#10.25.63.0/24
#100.25.0.3/16

Not in the Standard library for 2.5, but ipaddr makes this very easy. I believe it is in 3.3 under the name ipaddress.

import ipaddr

a = ipaddr.IPAddress('192.168.0.1')
n = ipaddr.IPNetwork('192.168.0.0/24')

#This will return True
n.Contains(a)

previous solution have a bug in ip & net == net. Correct ip lookup is ip & netmask = net

bugfixed code:

import socket
import struct

def makeMask(n):
    "return a mask of n bits as a long integer"
    return (2L<<n-1) - 1

def dottedQuadToNum(ip):
    "convert decimal dotted quad string to long integer"
    return struct.unpack('L',socket.inet_aton(ip))[0]

def addressInNetwork(ip,net,netmask):
   "Is an address in a network"
   print "IP "+str(ip) + " NET "+str(net) + " MASK "+str(netmask)+" AND "+str(ip & netmask)
   return ip & netmask == net

def humannetcheck(ip,net):
        address=dottedQuadToNum(ip)
        netaddr=dottedQuadToNum(net.split("/")[0])
        netmask=makeMask(long(net.split("/")[1]))
        return addressInNetwork(address,netaddr,netmask)


print humannetcheck("192.168.0.1","192.168.0.0/24");
print humannetcheck("192.169.0.1","192.168.0.0/24");

The choosen answer has a bug.

Following is the correct code:

def addressInNetwork(ip, net_n_bits):
   ipaddr = struct.unpack('<L', socket.inet_aton(ip))[0]
   net, bits = net_n_bits.split('/')
   netaddr = struct.unpack('<L', socket.inet_aton(net))[0]
   netmask = ((1L << int(bits)) - 1)
   return ipaddr & netmask == netaddr & netmask

Note: ipaddr & netmask == netaddr & netmask instead of ipaddr & netmask == netmask.

I also replace ((2L<<int(bits)-1) - 1) with ((1L << int(bits)) - 1), as the latter seems more understandable.

I’m not a fan of using modules when they are not needed. This job only requires simple math, so here is my simple function to do the job:

def ipToInt(ip):
    o = map(int, ip.split('.'))
    res = (16777216 * o[0]) + (65536 * o[1]) + (256 * o[2]) + o[3]
    return res

def isIpInSubnet(ip, ipNetwork, maskLength):
    ipInt = ipToInt(ip)#my test ip, in int form

    maskLengthFromRight = 32 - maskLength

    ipNetworkInt = ipToInt(ipNetwork) #convert the ip network into integer form
    binString = "{0:b}".format(ipNetworkInt) #convert that into into binary (string format)

    chopAmount = 0 #find out how much of that int I need to cut off
    for i in range(maskLengthFromRight):
        if i < len(binString):
            chopAmount += int(binString[len(binString)-1-i]) * 2**i

    minVal = ipNetworkInt-chopAmount
    maxVal = minVal+2**maskLengthFromRight -1

    return minVal <= ipInt and ipInt <= maxVal

Then to use it:

>>> print isIpInSubnet('66.151.97.0', '66.151.97.192',24) 
True
>>> print isIpInSubnet('66.151.97.193', '66.151.97.192',29) 
True
>>> print isIpInSubnet('66.151.96.0', '66.151.97.192',24) 
False
>>> print isIpInSubnet('66.151.97.0', '66.151.97.192',29) 

That’s it, this is much faster than the solutions above with the included modules.

Wherever possible I’d recommend the built in ipaddress module. It’s only available in Python 3 though, but it is super easy to use, and supports IPv6. And why aren’t you using Python 3 yet anyway, right?

The accepted answer doesn’t work … which is making me angry. Mask is backwards and doesn’t work with any bits that are not a simple 8 bit block (eg /24). I adapted the answer, and it works nicely.

    import socket,struct
    
    def addressInNetwork(ip, net_n_bits):  
      ipaddr = struct.unpack('!L', socket.inet_aton(ip))[0]
      net, bits = net_n_bits.split('/')
      netaddr = struct.unpack('!L', socket.inet_aton(net))[0]
      netmask = (0xFFFFFFFF >> int(bits)) ^ 0xFFFFFFFF
      return ipaddr & netmask == netaddr

here is a function that returns a dotted binary string to help visualize the masking.. kind of like ipcalc output.

    def bb(i):
     def s = '{:032b}'.format(i)
     def return s[0:8]+"."+s[8:16]+"."+s[16:24]+"."+s[24:32]

eg:

From various sources above, and from my own research, this is how I got subnet and address calculation working. These pieces are enough to solve the question and other related questions.

class iptools:
    @staticmethod
    def dottedQuadToNum(ip):
        "convert decimal dotted quad string to long integer"
        return struct.unpack('>L', socket.inet_aton(ip))[0]

    @staticmethod
    def numToDottedQuad(n):
        "convert long int to dotted quad string"
        return socket.inet_ntoa(struct.pack('>L', n))

    @staticmethod
    def makeNetmask(mask):
        bits = 0
        for i in xrange(32-int(mask), 32):
            bits |= (1 << i)
        return bits

    @staticmethod
    def ipToNetAndHost(ip, maskbits):
        "returns tuple (network, host) dotted-quad addresses given"
        " IP and mask size"
        # (by Greg Jorgensen)
        n = iptools.dottedQuadToNum(ip)
        m = iptools.makeMask(maskbits)
        net = n & m
        host = n - mask
        return iptools.numToDottedQuad(net), iptools.numToDottedQuad(host)

There is an API that’s called SubnetTree available in python that do this job very well.
This is a simple example :

import SubnetTree
t = SubnetTree.SubnetTree()
t.insert("10.0.1.3/32")
print("10.0.1.3" in t)

This is the link

import socket,struct
def addressInNetwork(ip,net):
    "Is an address in a network"
    ipaddr = struct.unpack('!L',socket.inet_aton(ip))[0]
    netaddr,bits = net.split('/')
    netaddr = struct.unpack('!L',socket.inet_aton(netaddr))[0]
    netmask = ((1<<(32-int(bits))) - 1)^0xffffffff
    return ipaddr & netmask == netaddr & netmask
print addressInNetwork('10.10.10.110','10.10.10.128/25')
print addressInNetwork('10.10.10.110','10.10.10.0/25')
print addressInNetwork('10.10.10.110','10.20.10.128/25')

$ python check-subnet.py
False
True
False

Here is my code

# -*- coding: utf-8 -*-
import socket


class SubnetTest(object):
    def __init__(self, network):
        self.network, self.netmask = network.split('/')
        self._network_int = int(socket.inet_aton(self.network).encode('hex'), 16)
        self._mask = ((1L << int(self.netmask)) - 1) << (32 - int(self.netmask))
        self._net_prefix = self._network_int & self._mask

    def match(self, ip):
        '''
        判断传入的 IP 是不是本 Network 内的 IP
        '''
        ip_int = int(socket.inet_aton(ip).encode('hex'), 16)
        return (ip_int & self._mask) == self._net_prefix

st = SubnetTest('100.98.21.0/24')
print st.match('100.98.23.32')

If you do not want to import other modules you could go with:

def ip_matches_network(self, network, ip):
    """
    '{:08b}'.format(254): Converts 254 in a string of its binary representation

    ip_bits[:net_mask] == net_ip_bits[:net_mask]: compare the ip bit streams

    :param network: string like '192.168.33.0/24'
    :param ip: string like '192.168.33.1'
    :return: if ip matches network
    """
    net_ip, net_mask = network.split('/')
    net_mask = int(net_mask)
    ip_bits = ''.join('{:08b}'.format(int(x)) for x in ip.split('.'))
    net_ip_bits = ''.join('{:08b}'.format(int(x)) for x in net_ip.split('.'))
    # example: net_mask=24 -> compare strings at position 0 to 23
    return ip_bits[:net_mask] == net_ip_bits[:net_mask]

Relying on the “struct” module can cause problems with endian-ness and type sizes, and just isn’t needed. Nor is socket.inet_aton(). Python works very well with dotted-quad IP addresses:

def ip_to_u32(ip):
  return int(''.join('%02x' % int(d) for d in ip.split('.')), 16)

I need to do IP matching on each socket accept() call, against a whole set of allowable source networks, so I precompute masks and networks, as integers:

SNS_SOURCES = [
  # US-EAST-1
  '207.171.167.101',
  '207.171.167.25',
  '207.171.167.26',
  '207.171.172.6',
  '54.239.98.0/24',
  '54.240.217.16/29',
  '54.240.217.8/29',
  '54.240.217.64/28',
  '54.240.217.80/29',
  '72.21.196.64/29',
  '72.21.198.64/29',
  '72.21.198.72',
  '72.21.217.0/24',
  ]

def build_masks():
  masks = [ ]
  for cidr in SNS_SOURCES:
    if '/' in cidr:
      netstr, bits = cidr.split('/')
      mask = (0xffffffff << (32 - int(bits))) & 0xffffffff
      net = ip_to_u32(netstr) & mask
    else:
      mask = 0xffffffff
      net = ip_to_u32(cidr)
    masks.append((mask, net))
  return masks

Then I can quickly see if a given IP is within one of those networks:

ip = ip_to_u32(ipstr)
for mask, net in cached_masks:
  if ip & mask == net:
    # matched!
    break
else:
  raise BadClientIP(ipstr)

No module imports needed, and the code is very fast at matching.

I tried one subset of proposed solutions in these answers.. with no success, I finally adapted and fixed the proposed code and wrote my fixed function.

I tested it and works at least on little endian architectures–e.g.x86– if anyone likes to try on a big endian architecture, please give me feedback.

IP2Int code comes from this post, the other method is a fully (for my test cases) working fix of previous proposals in this question.

The code:

def IP2Int(ip):
    o = map(int, ip.split('.'))
    res = (16777216 * o[0]) + (65536 * o[1]) + (256 * o[2]) + o[3]
    return res


def addressInNetwork(ip, net_n_bits):
    ipaddr = IP2Int(ip)
    net, bits = net_n_bits.split('/')
    netaddr = IP2Int(net)
    bits_num = int(bits)
    netmask = ((1L << bits_num) - 1) << (32 - bits_num)
    return ipaddr & netmask == netaddr & netmask

Hope useful,

For python3

import ipaddress
ipaddress.IPv4Address('192.168.1.1') in ipaddress.IPv4Network('192.168.0.0/24')
ipaddress.IPv4Address('192.168.1.1') in ipaddress.IPv4Network('192.168.0.0/16')

Output :

False
True

Using Python >= 3.7 ipaddress:

import ipaddress

address = ipaddress.ip_address("192.168.0.1")
network = ipaddress.ip_network("192.168.0.0/16")

print(network.supernet_of(ipaddress.ip_network(f"{address}/{address.max_prefixlen}")))

Explanation

You can think of an IP Address as a Network with the largest possible netmask (/32 for IPv4, /128 for IPv6)

Checking whether 192.168.0.1 is in 192.168.0.0/16 is essentially the same as checking whether 192.168.0.1/32 is a subnet of 192.168.0.0/16

Here is the solution using netaddr package

from netaddr import IPNetwork, IPAddress


def network_has_ip(network, ip):

    if not isinstance(network, IPNetwork):
        raise Exception("network parameter must be {0} instance".format(IPNetwork.__name__))

    if not isinstance(ip, IPAddress):
        raise Exception("ip parameter must be {0} instance".format(IPAddress.__name__))

    return (network.cidr.ip.value & network.netmask.value) == (ip.value & network.netmask.value)

As of Python 3.7, you can use subnet_of and supernet_of helper methods, which are part of the standard library:

To just test against a single IP, you can just use the subnet mask /32 which means "only this IP address" as a subnet, or you can pass the IP address to IPv4Nework or IPv6Nework constructors and they will return a subnet value for you.

So for your example:

from ipaddress import IPv4Network, IPv4Address

# Store IP Address as variable
>>> myip = IPv4Address('192.168.0.1')
>>> myip
IPv4Address('192.168.0.1')

# This treats the IP as a subnet
>>> myip_subnet = IPv4Network(myip)
>>> myip_subnet
IPv4Network('192.168.0.1/32')

# The other subnet to test membership against
>>> other_subnet = IPv4Network('192.168.0.0/24')
>>> other_subnet
IPv4Network('192.168.0.0/24')

# Now we can test
>>> myip_subnet.subnet_of(other_subnet)
True

Are there general tools in Python for ip address manipulation? Stuff
like host lookups, ip adddress to int, network address with netmask to
int and so on? Hopefully in the standard Python library for 2.5.

In Python 3, there’s the ipaddress module which has tools for IPv4 and IPv6 manipulation. You can convert them to an int, by casting, i.e. int(IPv4Address('192.168.0.1')). Lots of other useful functions in the ipaddress module for hosts, etc.

To avoid having builtin or third party modules change their syntax over time, I created my own that does this. I’m using this as an importable module. I hope this helps someone:

def subnet_lookup(subnet: str, netmask: str, ip_address: str):
    """
    :param subnet: subnet to test against (as string)
    :param netmask: mask of subnet
    :param ip_address: ip to test against subnet and mask

    :return True if a match; False if not a match

    Steps:

    1) convert entire subnet into one binary word
    2) convert entire mask into one binary word
    3) determine bcast from comparing subnet and mask
    4) convert entire ip_address into one binary word
    5) convert entire subnet into decimal
    6) convert entire bcast into decimal
    7) convert entire ip_address into decimal
    8) determine if ip_address falls between subnet and bcast using range(); returns True if yes, False if no
    """

    def convert_whole_to_bin(whole):
        ip_dec_list = whole.split(".")
        ip_bin_str = ""

        for ip in ip_dec_list:
            binary = dec_to_bin(int(ip))
            ip_bin_str += binary

        return ip_bin_str

    def dec_to_bin(decimal_octet: int):
        binary = bin(decimal_octet).replace("0b", "")

        return binary.rjust(8, '0')

    def split_binary_into_list(binary_octet: str):
        bin_list = []
        for s in binary_octet:
            bin_list.append(s)

        return bin_list

    def determine_bcast(subnet, netmask):
        subnet_split = split_binary_into_list(subnet)
        netmask_split = split_binary_into_list(netmask)
        bcast_list = []

        for subnet, mask in zip(subnet_split, netmask_split):
            if mask != '0':
                bcast_list.append(subnet)

            else:
                bcast_list.append('1')

        bcast_bin = "".join(bcast_list)

        return bcast_bin

    def bin_to_dec(binary_single_word: str):
        decimal = int(binary_single_word, 2)

        return decimal

    def subnet_lookup(ip_address, subnet, bcast):

        return ip_address in range(subnet, bcast + 1)

    # 1) convert entire subnet into one binary word
    subnet_single_bin = convert_whole_to_bin(whole=subnet)

    # 2) convert entire mask into one binary word
    mask_single_bin = convert_whole_to_bin(whole=netmask)

    # 3) determine bcast from comparing subnet and mask
    bcast_single_bin = determine_bcast(subnet=subnet_single_bin, netmask=mask_single_bin)

    # 4) convert entire ip_address into one binary word
    ip_address_single_bin = convert_whole_to_bin(whole=ip_address)

    # 5) convert entire subnet into decimal
    subnet_single_dec = bin_to_dec(binary_single_word=subnet_single_bin)

    # 6) convert entire bcast into decimal
    bcast_single_dec = bin_to_dec(binary_single_word=bcast_single_bin)

    # 7) convert entire ip_address into decimal
    ip_address_single_dec = bin_to_dec(binary_single_word=ip_address_single_bin)

    # 8) determine if ip_address falls between subnet and bcast; returns True if yes, False if no
    lookup_result = subnet_lookup(ip_address=ip_address_single_dec, subnet=subnet_single_dec, bcast=bcast_single_dec)

    return lookup_result


# Testing:

subnet = "172.16.0.0"
netmask = "255.255.0.0"
ip_address = "172.16.255.255"

result = subnet_lookup(subnet=subnet, netmask=netmask, ip_address=ip_address)

print(result)