compare amount paid in interest with/out extra payments

amort.py

@@ -21,6 +21,8 @@ def generate_amortization_schedule(principal, interest_rate, loan_term, extra_pa
         one_time_payment = extra_payments.pop(0)
     for payment_number in range(1, num_payments + 1):
         # Calculate interest for the current period
+        if remaining_balance == 0:
+            break
         interest_payment = round(remaining_balance * monthly_interest_rate, 2)
 
         # Calculate principal payment
@@ -32,7 +34,6 @@ def generate_amortization_schedule(principal, interest_rate, loan_term, extra_pa
             remaining_balance -= one_time_payment['amount']
             if extra_payments != []:
                 one_time_payment = extra_payments.pop(0)
-
         # Update remaining balance
         remaining_balance -= principal_payment
 
@@ -50,9 +51,27 @@ def generate_amortization_schedule(principal, interest_rate, loan_term, extra_pa
             'Remaining Balance': round(remaining_balance,2)
         }
         amortization_schedule.append(payment_details)
-
     return amortization_schedule
 
+def get_totals(amortization_schedule, display=False, export=False):
+    total_paid = 0
+    total_interest_paid = 0
+    total_principal_paid = 0
+    # Display the amortization schedule
+    if display:
+        print("id, paid, interest payment, principal payment, remaining")
+    for payment in amortization_schedule:
+        # print(payment)
+        total_paid += payment["Payment Amount"]
+        total_interest_paid += payment["Interest Payment"]
+        total_principal_paid += payment["Principal Payment"]  
+        if payment["Remaining Balance"] < 0:
+            break
+        attrs = [payment[key] for key in payment]
+        if display:
+            print("%s" % ", ".join([str(attr) for attr in attrs]))
+    return total_paid, total_interest_paid, total_principal_paid
+
 if __name__ == "__main__":
     # Example usage
     # principal = 100000
@@ -82,6 +101,13 @@ if __name__ == "__main__":
         extra.sort(key=lambda k: k["payment_number"])
         return args.principal, args.interest_rate, args.term, extra
 
+    def compare(with_extra_payments, without):
+        x,y,z = get_totals(with_extra_payments)
+        a,b,c = get_totals(without)
+        print(chr(916), "paid: ", round(a-x,2))
+        print(chr(916), "interest paid: ", round(b-y,2))
+        print(chr(916), "principal paid: ", round(c-z,2))
+
     principal, interest_rate, loan_term, extra_payments = get_arguments()
     
     # one_time_payment = {
@@ -90,23 +116,14 @@ if __name__ == "__main__":
     # }
 
     schedule = generate_amortization_schedule(principal, interest_rate, loan_term, extra_payments)
+    paid, interest_paid, principal_paid = get_totals(schedule, True)
 
-    total_paid = 0
+    print("total paid: ", round(paid,2))
-    total_interest_paid = 0
+    print("total interest paid: ", round(interest_paid,2))
-    total_principal_paid = 0
+    print("total principal paid: ", round(principal_paid,2))
 
-    # Display the amortization schedule
+    # without extra payments for comparison
-    print("id, paid, interest payment, principal payment, remaining")
+    compare(schedule, generate_amortization_schedule(
-    for payment in schedule:
+        principal, interest_rate, loan_term)
-        # print(payment)
+    )
-        total_paid += payment["Payment Amount"]
-        total_interest_paid += payment["Interest Payment"]
-        total_principal_paid += payment["Principal Payment"]  
-        if payment["Remaining Balance"] < 0:
-            break
-        attrs = [payment[key] for key in payment]
-        print("%s" % ", ".join([str(attr) for attr in attrs]))
 
-    print("total paid: ", round(total_paid,2))
-    print("total interest paid: ", round(total_interest_paid,2))
-    print("total principal paid: ", round(total_principal_paid,2))