Project description
This project describes an activity of updating a text file, based on the necessity of the business.
It is designed for a process to maintain allow-list-based access control list. In order to restrict access of unauthorized users, businesses are required to review the list and remove access privileges on a need-to basis. With a given list of IP addresses, the program will remove them from the allow-list and write IP addresses back to the text file.
Open the file that contains the allow list
Initially, the allow list text file contains IP addresses as follows.
ip address
192.168.25.60
192.168.205.12
192.168.97.225
192.168.6.9
192.168.52.90
192.168.158.170
192.168.90.124
192.168.186.176
192.168.133.188
192.168.203.198
192.168.201.40
192.168.218.219
192.168.52.37
192.168.156.224
192.168.60.153
192.168.58.57
192.168.69.116
Read the file contents
The following code piece will read the list file import_file. with statement
will handle the execution of open() and close() automatically.
# read the list from the file
with open(import_file, "r") as file:
ips = file.read()
Convert the string into a list
Then it splits the whole string into a list of strings. Each string represents an IP address.
# split IP addresses based on line breaks
ip_addresses = ips.split()
Iterate through the remove list
In order to remove all IP addresses from the list we want to maintain, it iterates over remove targets and removes them from the list.
# remove each target IP address from the list
for element in remove_list:
if element in ip_addresses:
ip_addresses.remove(element)
Update the file with the revised list of IP addresses
To write back to the file, we reformat the list into a line-break-separated single string. Write the text back.
# prepare updated string of list by inserting '\n' as separator
ip_addresses = "\n".join(ip_addresses)
# fully write back to the file
with open(import_file, "w") as file:
file.write(ip_addresses)
Summary
This project explained how to automate the maintenance of allow-list which contains IP addresses. For reusability, the whole process is formatted as a function. The docstring contains the signature of the function. Appropriate comments are inserted for future modifications or reviews.
def update_file(import_file, remove_list):
""" Removes target IP addresses from the text file.
If given target IP addresses are not in the text file, they are ignored.
Parameters
----------
import_file : str
File path/name of the list we want to remove from
remove_list : list (of str)
Target IP addresses we want to remove
"""
# read the list from the file
with open(import_file, "r") as file:
ips = file.read()
# split IP addresses based on line breaks
ip_addresses = ips.split()
# remove each target IP address from the list
for element in remove_list:
if element in ip_addresses:
ip_addresses.remove(element)
# prepare updated string of list by inserting '\n' as separator
ip_addresses = "\n".join(ip_addresses)
# fully write back to the file
with open(import_file, "w") as file:
file.write(ip_addresses)
The following code piece is an example of its execution.
# sample execution:
# call the function
update_file("allow_list.txt", ["192.168.25.60", "192.168.90.124", "192.168.60.153"])
# Build `with` statement to read in the updated file
with open("allow_list.txt", "r") as file:
# Read in the updated file and store the contents in `text`
text = file.read()
# Display the contents of `text`
print(text)
The output is:
ip
address
192.168.205.12
192.168.97.225
192.168.6.9
192.168.52.90
192.168.158.170
192.168.186.176
192.168.133.188
192.168.203.198
192.168.201.40
192.168.218.219
192.168.52.37
192.168.156.224
192.168.58.57
192.168.69.116
For future maintenance, it is suggested to:
- Instead of reading while list from the text, we can perform a rewrite based on chunks, in order to handle a large list
- Sorting the IP addresses both in the list and the target list will reduce the complexity of execution.