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Cash_Register.py

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+'''
+ Author: Connor Johnson
+ Completed: 09/06/2021
+ Contains the main code to be run for the Cash Register project
+'''
+
+import sys
+from calculate_change import *
+
+# Read in data from text file
+with open(sys.argv[1], 'r') as f:
+    lines = f.readlines()
+
+
+# Loop through each line in the text file
+counter = 0 # Counter for tracking which line the loop is on
+for s in lines:
+    counter = counter + 1
+
+    # Input from text file is checked that it's formatted correctly and values are assigned
+    nums = s.split(",")
+    if len(nums) != 2:
+        print("Line " + str(counter) + " of input.txt must contain 2 numbers separated by a comma.")
+        continue
+    try:
+        cents = float(nums[1]) - float(nums[0])   #Calculate the change to be given
+    except ValueError:
+        print("Line " + str(counter) + " of input.txt must contain 2 numbers separated by a comma.")
+        continue
+
+    cents = int(cents*100+0.5)  # Change cents to an integer that represents the total cents in change
+
+    final_change = calculate_change(cents)
+    if final_change == None:
+        print("Invalid Input. Total due can't be more than amount paid.")
+    else:
+        print(final_change[0])
+
+
+

README.txt

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+Connor Johnson
+Cash Register Project
+Completed: 09/06/2021
+
+
+This project is used to find the coins that would be needed to give a certain amount of change. It takes a text file as input that should contain a list of values.
+Each line in the text file should contain 2 numbers separated by a comma. The first number is the price of something that is being payed for. The second number is the amount
+of money that the customer payed with. The program takes these numbers and returns the change that should be given back to the customers in dollars and coins. It normally
+gives change in the least possible number of coins, except when the total change in cents is divisible by three. In this case, the different denominations of change given
+is randomized while still adding up to the correct amount of change. If any lines in the input file are formatted incorrectly, they will be skipped, and the user will be
+notified of the incorrectly formatted lines. The test python file contains unit tests to make sure the calculate change method works correctly for a range of values.
+
+Files: Cash_Register.py, calculate_change.py, calculate_change_test.py
+
+Cash_Register.py: This is the file that contains the main and is used to the run the applicaiton.
+calculate_change.py: Contains a method that calculates the change and is called by Cash_Register.py
+calculate_change_test.py: Contains a few unit tests to test the functionality of calculate_change.py
+
+Running the application: Type the following command in the terminal
+python Cash_Register.py [filename]
+Example: python Cash_Register.py input.txt
+
+Example Input:
+1.33, 2.00
+2.71,4.00
+1.45,%4.00^
+1.50
+
+Example Output:
+2 quarters, 1 dime, 1 nickel, 2 pennies
+3 quarters, 1 dime, 1 nickel, 39 pennies
+Line 3 of input.txt must contain 2 numbers separated by a comma.
+Line 4 of input.txt must contain 2 numbers separated by a comma.
+
+Modules: random, numpy, sys
+
+Known Bugs: There are currently no known bugs contained in this project.

calculate_change.py

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+'''
+ Author: Connor Johnson
+ Completed: 09/06/2021
+ Contains the calculate_change method used in Cash_Register.py
+'''
+
+import random
+
+# Names and values of coin denominations, pennies are excluded because they are handled differently
+coin_values = [100, 25, 10, 5]
+coin_names = ['dollar', 'quarter', 'dime', 'nickel'] 
+
+
+def calculate_change(cents):
+    '''
+    calculate_change takes an amount in cents and calculates the change in coins that would be given for this amount
+    cents: The amount of cents in change as an integer
+    return: Returns a tuple containing a string that has the description of change and a list containing the value of each denomination; dollars, quarters, etc.
+            Returns None if cents is not a positive integer
+    '''
+    # Checks that cents is a positive integer
+    if type(cents) != int or cents < 0:
+        return None
+    # Handles if cents is equal to zero
+    if cents == 0:
+        return ('No change', [0,0,0,0,0])
+
+    coin_string = ''                # Final string to be returned
+    div_by_3 = cents%3 == 0   # Boolean variable that is true if the total change is divisible by 3
+
+    coin_cents = [0] * 5     # Tracks the number of each denomination, will be returned by this function
+
+    for i in range(0,4):
+        # Number of each denomination is determined, picked randomly if the total cents is divisible by 3
+        if(div_by_3):
+            num_coins = random.randint(0,int(cents/coin_values[i]))
+            cents = cents - num_coins*coin_values[i]
+        else:    
+            num_coins = int(cents/coin_values[i])
+            cents = cents%coin_values[i]
+
+        coin_cents[i] = num_coins
+
+        if num_coins == 0:  # Add nothing to string if number of that coin type is zero
+            continue  
+
+        # Add the number of each denomination to the final string
+        coin_string = coin_string + str(num_coins) + ' ' +  coin_names[i]
+        if num_coins > 1:
+            coin_string = coin_string + 's'
+        coin_string = coin_string + ', '
+
+    # All remaining cents are set as pennies
+    coin_cents[4] = cents
+    if cents > 0:
+        coin_string = coin_string + '1 penny' if cents == 1 else coin_string + str(cents) + ' pennies'
+
+    # The resulting string and array of coins is returned
+    return (coin_string, coin_cents)

calculate_change_test.py

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+'''
+ Author: Connor Johnson
+ Completed: 09/06/2021
+ Contains some unit tests for calculate_change method
+'''
+
+from calculate_change import *
+import numpy
+
+coin_values = [100, 25, 10, 5, 1]
+
+# Testing a range of positive values
+for t in range(0, 500):
+    change = numpy.dot(calculate_change(t)[1], coin_values)
+    assert change == t, "Change is not the correct amount. Should be " + str(t) + ", but return is " + str(change)
+
+# Testing a range of negative values
+for t in range(-100, 0):
+    assert calculate_change(t) == None, "Method should return None since it is passed a negative integer"
+
+# Testing a non integer argument
+assert calculate_change("some_string") == None, "Method chould return none since it is passed a non integer"