Assignment 1 Solution

Brief Description

You will write a program that allows the user to manage their finances. The program will be able

to record the user's incomes and expenses, display how their balance has changed, etc. It will also

need to be able to handle regular incomes and expenses; for example, the user will be able to

specify that they have a $100 income every Sunday, or that they spend $40.50 every Thursday.

Implementation details

Your program will be written in Python 3. The only modules you may import are sys and the

function.py file which you will write yourself.

Submission

You will submit your code on the assignment page on Ed. To make a submission, you will need to

press the "Mark" button. You may submit as many times as you wish without penalty - we will

mark the last submission that you make. After each submission, the marking system will

automatically check your code against the public test cases.

Please ensure you carefully follow the assignment specification. Your program output must

exactly match the output shown in the examples.

Warning: Any attempts to deceive or disrupt the marking system will result in an immediate zero

for the entire assignment. Negative marks can be assigned if you do not properly follow the

assignment specifications, or your code is unnecessarily or deliberately obfuscated.

Help and feedback

You are encouraged to ask questions about the assignment during the Helpdesk and on the Ed

discussion board; however, remember that you should not be posting any assignment code

publicly, as this would constitute academic dishonesty.




The Program

Starting the Program

The program will be given 1 extra command line argument when it is run:

$ python3 tracker.py <filename

This <filename will specify a file with information about regular incomes and expenses; see the

section on Regular Transactions for more information (it is recommended that you implement

this feature last).

After handling this file, the program will ask the user for their starting balance, like so:

Starting balance: $

The user will then fill out this field with their initial balance, for example:

Starting balance: $4.11

If the starting value cannot be converted to a float, the program should print Error:

Cannot convert to float! and quit immediately.

Starting balance: $cat

Error: Cannot convert to float!

If the starting value is negative or zero, the program should print Error: Must start with

positive balance! and quit immediately.

Starting balance: $-5

Error: Must start with positive balance!

Once we have the regular payments and initial balance set up, we're good to go! The program

should now continually ask for input, like so:

Enter command:

Depending on what the user enters, the program will record new transactions, show some

statistics, etc. For example, if the user types transaction ...

Enter command: transaction

...then the transaction operation (explained below) should execute. The program should

continue asking for more inputs indefinitely, and execute the appropriate code each time.Operations

transaction

Records a new income or expense transaction.

The program should ask the user how much money was involved in the transaction, like so:

Enter amount: $

The user should then be able to type in how much they earned or spent. Positive values represent

income, and negative values represent expenses.

Enter amount: $5.95

Enter amount: $-2.35

This value should then be reflected in the user's balance; for example, if they originally had $5 but

made a transaction of -$3, the user would now have $2.

However, if the value the user types in cannot be converted to a float, the program should print

Error: Cannot convert to float! and ask for another command.

Enter amount: $cat

Error: Cannot convert to float!

Enter command:

next

Advances to the next day, making sure the user is not in debt.

If the user has strictly less than $0, the program should print Oh no! You're in debt! and quit

immediately. Otherwise, it should print Going to the next day... and start a new day.

In this program, we start at day 0 and increase the day number by 1 every time the next

command is executed.




status

Displays a summary of how the day is going so far.

The program should print the following message:

Day <day number (<weekday)

Starting balance: $<starting balance

Current balance: $<current balance

Here,

<day number is the current day number of the program. As explained above, this starts at

0 and increases by 1 for every day that passes.

<weekday is which weekday it currently is, abbeviated to three letters; Sun for Sunday,

Mon for Monday, etc. In this program, day 0 is always a Sunday, day 1 is a Monday, and so

on. Day 6 would be a Saturday and day 7 is a Sunday again. (The weekdays list in the

scaffold may be useful here.)

<starting balance is the amount of money we had at the start of the day, before any

transactions (including regular transactions) were made. It should be displayed rounded to

exactly 2 decimal places.

<current balance is the amount of money we currently have, including all the

transactions we have made that day. It should be displayed rounded to exactly 2 decimal

places.

If the current balance is greater than the starting balance, the program should also print Nice

work! You're in the black. . Conversely, if the current balance is less than the starting

balance, the program should print Be careful! You're in the red. . If the current balance is

the same as the starting balance, no extra message needs to be printed.

Here are some examples:

Day 0 (Sun)

Starting balance: $5.00

Current balance: $6.00

Nice work! You're in the black.

Day 5 (Fri)

Starting balance: $55.00

Current balance: $54.50

Be careful! You're in the red.

Day 30 (Tue)

Starting balance: $120.00

Current balance: $120.00regular

Displays a summary of the regular transactions.

Please see the section on "Regular Transactions" to see how these values will be specified.

The program should print Regular Transactions: ; then, for every weekday, the program

should show a summary of the regular transactions in the following format:

<weekday: +$<regular income -$<regular expense

Here,

<weekday is the weekday abbreviated to three letters.

<regular income is the income the user regularly earns for that weekday. It should be

displayed rounded to exactly 2 decimal places.

<regular expense is the expense the user regularly has for that weekday. It should be

displayed rounded to exactly 2 decimal places.

Here is an example:

Regular Transactions:

Sun: +$5.00 -$4.00

Mon: +$3.00 -$2.00

Tue: +$7.35 -$1.00

Wed: +$0.00 -$0.00

Thu: +$14.90 -$5.00

Fri: +$6.00 -$3.00

Sat: +$6.00 -$5.00

help

Shows a list of availabile commands.

The program should print the following message:

The available commands are:

"transaction": Record a new income or expense

"next": Move on to the next day

"status": Show a summary of how you're doing today

"regular": Show a summary of your regular transactions

"help": Show this help message

"quit": Quit the programquit

Quits.

The program should print Bye! and quit.

Enter command: quit

Bye!

Anything else

If any command other than those specified above is entered, the program should simply print the

following message:

Command not found.

Use the "help" command for a list of available commands

The program should then continue prompting for commands.

Regular Transactions

Regular transactions are incomes and expenses that are automatically made on specific days of

the week - for example, the user might always earn $100 on Sundays and spend $40.50 on

Thursdays, which the program should automatically process. To implement these regular

transactions, you need to follow these three steps:

Step 1: Write the function process_file in the function.py file. This function should take one

string as an argument, open the file specified by this string and read the details of the regular

transactions described in this file. You can assume that the file will always be in the following

format, with exactly 14 lines and each line being convertible to a float without error:

<Sunday income

<Sunday expense

<Monday income

<Monday expense

...

<Friday income

<Friday expense

<Saturday income

<Saturday expense

All values in this file will be given as positive values; so if the user had a regular income of $100 on

Sundays and a regular expense of $40.50 on Thursdays, our file would look like this:100

0

0

0

0

0

0

0

0

40.50

0

0

0

0

The function should return a tuple of two lists, both of length 7; the first one being the regular

incomes throughout the week, and the second one being the regular expenses throughout the

week.

For example, if the string given to the function specified the file above, it should return ([100.0,

0.0, 0.0, 0.0, 0.0, 0.0, 0.0], [0.0, 0.0, 0.0, 0.0, 40.5, 0.0, 0.0]) . Make sure

your tuple contains lists of floats, not lists of strings.

However,

If the file specified by the parameter doesn't exist, the function should raise a ValueError

with the content of that error being the message Error: String does not represent a

valid file! .

Step 2: At the start of your main code, use the process_file function to get the 2 lists

containing the details of the regular incomes and expenses. The filename to be used as the

parameter for this function will be specified as a command line argument when running the

program.

$ python3 tracker.py <filename

You will need to make sure you include the line from function import process_file at the

top of your main code so that you can use the process_file function you wrote in part 1.

However,

If the required command line argument is not given, the program should print Error: Not

enough command line arguments! and quit immediately.

If the process_file function raises a ValueError, the program should print Error: File

not found! and quit immediately.

Step 3: Ensure your program automatically adds the regular income and subtracts the regular

expenses for the appropriate weekday at the start of every day.Examples

Regular Transaction Files

no_regular_transactions.txt :

0

0

0

0

0

0

0

0

0

0

0

0

0

0

sample_regular_transactions.txt :

5

4

3

2

7.35

1

0

0

14.9

5

6

3

6

5Program Executions

Normal Case 1:

$ python3 tracker.py no_regular_transactions.txt

Starting balance: $100.50

Enter command: transaction

Enter amount: $10

Enter command: status

Day 0 (Sun)

Starting balance: $100.50

Current balance: $110.50

Nice work! You're in the black.

Enter command: next

Going to the next day...

Enter command: status

Day 1 (Mon)

Starting balance: $110.50

Current balance: $110.50

Enter command: regular

Regular Transactions:

Sun: +$0.00 -$0.00

Mon: +$0.00 -$0.00

Tue: +$0.00 -$0.00

Wed: +$0.00 -$0.00

Thu: +$0.00 -$0.00

Fri: +$0.00 -$0.00

Sat: +$0.00 -$0.00

Enter command: transaction

Enter amount: $-3

Enter command: transaction

Enter amount: $-10.2

Enter command: status

Day 1 (Mon)

Starting balance: $110.50

Current balance: $97.30

Be careful! You're in the red.

Enter command: quit

Bye!Normal Case 2:

$ python3 tracker.py sample_regular_transactions.txt

Starting balance: $10.00

Enter command: next

Going to the next day...

Enter command: next

Going to the next day...

Enter command: next

Going to the next day...

Enter command: next

Going to the next day...

Enter command: status

Day 4 (Thu)

Starting balance: $18.35

Current balance: $28.25

Nice work! You're in the black.

Enter command: transaction

Enter amount: $100

Enter command: quit

Bye!

Invalid Command:

$ python3 tracker.py no_regular_transactions.txt

Starting balance: $5

Enter command: STATUS

Command not found.

Use the "help" command for a list of available commands

Enter command: exit

Command not found.

Use the "help" command for a list of available commands

Enter command: quit

Bye!Going into Debt:

$ python3 tracker.py no_regular_transactions.txt

Starting balance: $5

Enter command: transaction

Enter amount: $-10

Enter command: status

Day 0 (Sun)

Starting balance: $5.00

Current balance: $-5.00

Be careful! You're in the red.

Enter command: transaction

Enter amount: $6

Enter command: status

Day 0 (Sun)

Starting balance: $5.00

Current balance: $1.00

Be careful! You're in the red.

Enter command: next

Going to the next day...

Enter command: transaction

Enter amount: $-10

Enter command: status

Day 1 (Mon)

Starting balance: $1.00

Current balance: $-9.00

Be careful! You're in the red.

Enter command: next

Oh no! You're in debt!

Non-existent File

$ python3 tracker.py nonexistent.txt

Error: File not found!Unable to Interpret Transaction as Float

$ python3 tracker.py no_regular_transactions.txt

Starting balance: $10.50

Enter command: transaction

Enter amount: $cat

Error: Cannot convert to float!

Enter command: quit

Bye!

Hints and Extra Information

You should always print an empty line directly before asking the user for a command.

Commands are case-sensitive. For example, quit is valid, but QUIT is invalid.

To print a string containing single quotes, enclose it in double quotes, and vice versa (or put

a backslash before it).

Use the modulo operator ( % ) to your advantage. It can help you keep track of weekdays!

For the purposes of this assignment, you can treat all monetary values as floats - none of the

test cases will cause floating point errors.Marking

7 marks will be given for passing the automated test cases. There are a total of 28 tests, and

you will receive 0.5 marks for every 2 that you pass (quarter marks will not be given).

3 marks will be given for a manual inspection of code. You should ensure that your code

uses meaningful variable names, good structure, and helpful and concise comments to

clarify the intentions of the code.