Update a file through a Python algorithm

Project description

As part of my role, I am required to regularly update a file that identifies the employees who can access restricted content. The contents of the file are based on who is working with personal patient records. Employees are restricted access based on their IP address. There is an allow list for IP addresses permitted to sign into the restricted subnetwork. There's also a remove list that identifies which employees you must remove from this allow list.

My task is to create an algorithm that uses Python code to check whether the allow list contains any IP addresses identified on the remove list. If so, the algorithm should remove those IP addresses from the file containing the allow list.

Assigning the "allow" and "remove" list to variables



Code block:
import_file = "allow_list.txt"
remove_list = "remove_list.txt"

with open(import_file, "r")as file:

with open(remove_list, "r")as file:

Code review: In my algorithm, the with statement is used with the .open() function in read mode to open the allow and remove list file for the purpose of reading it. The purpose of opening the file is to allow me to access the IP addresses stored in the allow list file. The with keyword will help manage the resources by closing the file after exiting the with statement. In the code with open(import_file, "r") as file:, the open() function has two parameters. The first identifies the file to import, and then the second indicates what I want to do with the file. In this case, "r" indicates that I want to read it. The code also uses the as keyword to assign a variable named file; file stores the output of the .open() function while I work within the with statement.


Read the files content



Code block:
with open(import_file, "r")as file:
allow_ips = file.read()
with open(remove_list, "r")as file:
remove_ips = file.read()

Code review: While utilizing the .open() function with the "r" argument for reading, I can invoke the .read() function within the with statement. This method converts the file content into a string, enabling me to access it. I utilized the .read() method on the file variable defined within the with statement. Subsequently, I stored the resulting string in the variable ip_addresses and remove_ips.


Convert the string into a list



Code block:
allow_ips = allow_ips.split()
remove_ips = remove_ips.split()

Code review: In order to remove individual IP addresses from the allow list, I needed it to be in list format. Therefore, I next used the .split() method to convert the ip_addresses and remove_ips strings into a list: Appending the .split() function to a string variable triggers its operation, converting the string's contents into a list. The intent behind splitting ip_addresses and remove_ips into a list is to facilitate the removal of IP addresses from the allow list. By default, the .split() function separates text by whitespace, generating individual list elements. Within this algorithm, the .split() function processes the data held in the variable ip_addresses, containing a string of IP addresses separated by whitespaces, transforming it into a list of IP addresses. To retain this list, I reassigned it to the variable ip_addresses.


Iterate through the remove list



Code block:
for element in allow_ips:

Code review: To facilitate a crucial component of my algorithm, I implemented an iterative process that involves cycling through the IP address enlisted in the remove_list. To do this, I incorporated a for loop.

In Python, the for loop duplicates code for a designated sequence. In a Python algorithm, such as this one, the primary intention of the for loop is to execute precise code statements for each element within a sequence. The for keyword initiates the loop, followed by the loop variable element and the keyword in. The use of the keyword in denotes the iteration through the sequence ip_addresses, assigning each value to the loop variable element.


Remove IP addresses that are on the remove list



Code block:
for element in allow_ips:
   if element in remove_ips:
       allow_ips.remove(element)

Code review: To implement my algorithm, it was necessary to eliminate any IP address from the allow list, named ip_address, that also appeared in the remove_list. Since there were no duplicates within ip_addresses, the previous code sufficied for this task.

Initially, in my for loop, I established a condition to check if the loop variable element was present in the ip_addresses list. This step was crucial to prevent errors that could arise from applying .remove() to elements not found within ip_addresses.

Subsequently, within that condition, I utilized .remove() on ip_addresses, passing the loop variable element as the argument. This approach ensured the removal of each IP address listed in remove_list from ip_addresses.


Update the file with the revised list of IP addresses



Code block:
allow_ips = "\n".join(allow_ips)

Code review: For the last stage of my algorithm, I had to revise the list of IP addresses in the allow list file. To achieve this, I began by coverting the list back into a string. I utilized the .join() method for this purpose.

The .join() method amalgamates all elements in an iterable into a single string. This method operates on a string comprising characters that will separate the elements in the iterable when combined. In the present algorithm, I utilized the .join() method to fashion a string from the list of ip_addresses. This string was then passed as an argument to the .write() method during the writing process for the "allow_list.txt" file. I designated the string ("\n") as the separator, instructing Python to place each element on a new line.

Subsequently, I implemented another with statement along with the .write() method to effectuate the file update.




Code block:
with open(import_file, 'w') as file:
   file.write(allow_ips)

Code review: This time, I added a second argument, "w", to the open() function within the statement. This argument signifies my intention to open a file for writing, thus overwriting its existing contents. When "w" is used, I can employ the .write() function within the with statement's body. The .write() function is responsible for writing string data to a designated file, replacing any prior content.

In this scenario, my aim was to write the updated allow list as a string to the "allow_list.txt" file. By doing this, any IP addresses removed from the allow list would no longer have access to the restricted content. To overwrite the file, I appended the .write() function to the file object, which I designated in the with statement. I passed the ip_addresses variable as an argument, indicating that the contents of the file specified in the with statement should be replaced with the data from this variable.


Summary

I devised an algorithm to eliminate IP addresses from the "allow_list.txt" file, as specified in the "remove_list.txt" file. This process commenced with the opening of the file, followed by its conversion into a readable string. Subsequently, this string was transformed into a list stored in the variable ip_address.

Next, I iterated throught the IP addresses in remove_list. During each iteration, I checked if the element existed within the ip_addresses list. If It did, I utilized the .remove() method to eliminate the specific element from ip_addresses. Upon completion, I employed the .join() method to convert ip_addresses back into a string. This enabled me to overwrite the contents of the "allow_list.txt" file with the updated list of IP addresses.


Find the complete code at my Github repository