As a fictitious healthcare company's security professional, I regularly updated a file listing employees authorized to access restricted content based on their handling of patient records. Access was restricted by IP address, with an allow list for permitted IPs and a remove list for exclusions. My task was to develop a Python algorithm to remove IPs listed on the remove list from the "allow_list.txt".
I initially opened the "allow_list.txt" file, assigning it's file name as a string to the import_file variable.
I then used a with statement to open the file.
I used the "with" statement with the ".open()" function in read mode to access the allow list file for reading purposes. This allows me to retrieve the IP addresses stored in the file. The "with" keyword ensures proper resource management by automatically closing the file after exiting the statement block. The code snippet has two parameters: the first specifies the file to import, and the second indicates the desired file operation - in this case, "r" denotes reading mode.
I used the .read() method to convert the file contents into a string to be read.
To transform individual IP addresses into a list format for removal from the allow list, I utilized the .split() method to convert the ip_addresses string. This method, when appended to a string variable, splits its contents into a list, simplifying subsequent IP removal operations. By default, .split() divides text by whitespace into list elements. In this case, it transformed the ip_addresses string, containing whitespace-separated IP addresses, into a list. This list was then reassigned to the ip_addresses variable.
Iterating through IP addresses listed in the remove_list was achieved through a for loop. This loop iterated over the sequence of IP addresses stored in the ip_addresses list, applying specific operations to each element.
Utilizing a conditional statement within this loop, I verified if each IP address from the remove_list existed in the ip_addresses list. Upon confirmation, the .remove() method was applied to delete the IP address from ip_addresses.
To finalize the algorithm, updating the allow list file with the revised list of IP addresses was necessary. Firstly, the list had to be converted back into a string format, accomplished using the .join() method, which concatenates elements of an iterable into a single string with specified separators.
Employing .join() on the ip_addresses list allowed me to create a string with each IP address on a separate line (using the string "\n" as a separator), ideal for updating the "allow_list.txt" file.
The with statement and .write() method facilitated this update, with the "w" argument indicating the intention to overwrite the file contents. By appending .write() to the file object within the with statement, I replaced the file's previous content with the updated ip_addresses data, thereby ensuring restricted content accessibility only to approved IP addresses.
I developed an algorithm to eliminate IP addresses listed in a remove_list variable from the "allow_list.txt" file, which contains approved IP addresses. The process involved opening the file, converting its contents into a readable string, and subsequently transforming this string into a list stored as the variable ip_addresses. Next, I iterated through the IP addresses in remove_list, checking if each element existed in the ip_addresses list. Upon confirmation, I utilized the .remove() method to delete the element from ip_addresses. Following this, I used the .join() method to convert ip_addresses back into a string format, allowing me to overwrite the contents of the "allow_list.txt" file with the updated list of IP addresses.