"For your final challenge in this unit, you will load two files. The first file F1 will have information about some accounts. It will be pipe-delimited and have one record per line, with these fields: ACCOUNT NUMBER | PIN CODE | BALANCE The second file F2 will contain instructions: one on each line. The instructions will look like this: COMMAND | AMOUNT | ACCOUNT NUMBER | PIN CODE COMMAND will be either add or sub. If the command is add, you will add AMOUNT to the BALANCE in the account files F1. If the command is sub, you will subtract."

Python script explained below. Highlighted comment important for proper running of code

Explanation:

# Get the filepath from the command line

import sys, os

#if you get an error message via the above,

#Change the import sys at the top to

#import sys, os from collections import OrderedDict

from collections import OrderedDict

# The command-line arguments

F1 = sys.argv[1]

F2 = sys.argv[2]

# Your code goes here

#empty dictionary for holding pin_code data read from F1

balance_dict = OrderedDict()

#iterate through each line in F1 and store in the balance_dict with account_number number as the key

#handle the case in which the file doesn't or the path is wrong

try:

   #open F1 for reading

   with open(F1, 'r') as balance_file:

       for line in balance_file.readlines():

           #split the line by "|", and store data, strip any extra white spaces

           account_number, pin_code, balance = line.strip().split("|")

           #strip white spaces for each variables

           account_number = account_number.strip()

           pin_code = pin_code.strip()

           balance = int(balance .strip())

           #store the values into the dictionary

           balance_dict[account_number] = { "pin_code" : pin_code, "balance" : balance }

   #open F2 for reading

   with open(F2, 'r') as transaction_file:

       #go through each line of F2

       for line in transaction_file.readlines():

           #extract data

           command, amount, account_number, pin_code = line.strip().split("|")

           #strip each variable string of extra white spaces, and convert into proper types as well

           command = command.strip()

           amount = int(amount.strip())

           account_number = account_number.strip()

           pin_code = pin_code.strip()

           #handle the case in which the key doesn't exist in the dict

           try:

               #check the given pin_code matches or not

               if pin_code == balance_dict[account_number]["pin_code"]:

                   #check what the command is

                   if command.lower() == "add":

                       #add amount to balance

                       balance_dict[account_number]["balance"] += amount

                   elif command.lower() == "sub":

                       #compute balance

                       new_balance = balance_dict[account_number]["balance"] - amount

                       #check if balance is negative or not

                       if new_balance >= 0:

                           #if not, update

                           balance_dict[account_number]["balance"] -= amount

           except KeyError:

               print("Oops!! Account number doesn't exist in F1")

   #open F1 for writing updated balances

   with open(F1, 'w') as balance_file:

       #go through each item in balance_dict

       for key in balance_dict:

           #construct the line to write to F1

           line = key + "|" + balance_dict[key]["pin_code"] + "|" + str(balance_dict[key]["balance"]) + os.linesep

           balance_file.write(line)

except IOError:

   print("Either a file doesn't exist or a path is wrong!!")