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140 lines
5.6 KiB
140 lines
5.6 KiB
# ProFin - Personal Finance Projector
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```
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__
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o /' )
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/' ( ,
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__/' PRO ) .' `;
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o _.-~~~~' ``---..__ .' ;
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_.--' b) ``--...____.' .'
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( _. )). `-._ <
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`vvvvvvv-)-.....___.- `-. __...--'-.'.
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`^^^^^'-------.....`-.___.'----... .' `.;
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jgs `-` `
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```
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ProFin is a python module for projecting the balance of a personal savings account
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over a future period.
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The output can be used to visualise the balance development when planning some big
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purchase or a change of the living situation, such as buying a flat or a car,
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getting a new job with possible months of no income, etc.
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Please note the script is intended only for orientation and there may be minor
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inaccuracies or bugs (please report!)
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## Supported Features
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### Financial Operations & Schemes
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- Once-off expenses and income
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- Recurrent monthly payments / income at a fixed date
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- Monthly payments with a total expense cap
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- Skipping a month in monthly payments / income
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- Spread monthly expenses (e.g. food cost) - distributed over all days in a month
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- Simple loan (borrowing money from a friend) with back-payments
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- Setting initial or correction balance
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### Functions
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- Setting up a financial situation with changes at arbitrary dates
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- Simulating account balance with day granularity
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- Plotting results using PyPlot
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**Example with Betty's car purchase**
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*(note: spreading was switched off for a more readable display here, so the values are slightly different from the graph below which has spreading enabled)*
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## Dependencies
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The script uses NumPy, MatPlotLib and Pandas for plotting. This may be improved in a future version
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(in particular Pandas could be replaced).
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If plotting is not needed and the dependencies are not available (e.g. some old Debian),
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remove their imports and comment out the graph() function
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## Examples
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See the example files for an example of usage. (The examples are silly and not very representative, but they show the API well).
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Additionally the code is documented with doc comments.
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### Usage example
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ProFin is used by writing a configuration script in Python. First create the projector:
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```python
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import profin
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pf = profin.Projector()
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```
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Now set the initial balance and the start date. This is the start of the simulation, which is done day by day.
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This is a fluent API, date() returns self.
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```python
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pf.date(2018, 'March', 24).balance(+40_000)
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```
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The next part is setting up recurrent and once-off expenses and incomes and their changes. This will be
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better explained below. The last bit is where we run the simulation:
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```python
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samples = pf.project_to(2019)
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pf.graph(samples)
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```
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samples is an array of record when the abalnce changed that we cna plot using the graph() method.
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## API overview
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ProFin works with two types of objects: the profiler, and incomes. Expense is a negative income and is internally
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represented the same way.
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### Projector API
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- `pf.date(year, month, day)` - set time cursor. This is used for subsequently created incomes as a starting date, or
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for their `.start()` and `.end()` methods when used without arguments. Day is optional and defaults to 1
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- `pf.project_to(year, month, day, verbose)` - Run the simulation. month, day and verbose are optional, `month` and `day`
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are by default Dec 31, `verbose` is True. `verbose` defines if we want to show updates in stdout when simulating. Returns a array of `samples` for plotting.
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- `pf.graph(samples, currency)` - draw samples from `project_to()` using pyplot. Currency is appended to values for display only
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- `pf.balance(money)` - set balance. when called in places other than at the beginning, this resets the balance at the given date resulting in a
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sharp change in the graph.
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- `pf.monthly(name, income, day=1)` - define a monthly income or expense of monthly value `income`, paid on day `day`.
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This returns a MonthlyIncome object. Name describes the income / expense in the stdout log.
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- `pf.single(name, money)` - once-off income or expense, returns a `SingleIncome`.
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- `pf.expend(name, money)`, `pf.receive(name, money)` - aliases of `single` that also ensure the money value has the right sign
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- `pf.borrow(name, money)` - describes a received interestless loan, returns a `SimpleLoan`.
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### MonthlyIncome API
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- `mi.on(day)` - set the pay day in the month, returns self
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- `mi.skip_month(year, month)` - skip a month's payment, return self
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- `mi.start(year, month, day)` - set start date (month, day default to Jan 1), return self.
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If no args given, take current cursor's date
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- `mi.end(year, month, day)` - end the payments. If no args given, take last day of current cursor's month
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- `mi.total(total)` - set a total money cap, after it's exhausted the payments stop
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- `mi.spread(yes=True)` - enable or disable spreading. This distributes the price across the month's days for a more realistic graph in some cases
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### SingleIncome API
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- `si.on(year, month, day)` - set the date of the payment, default - use cursor's date. month and day default to Jan 1
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### SimpleLoan API
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This is a composite income that is made up of a SingleIncome and a MonthlyIncome with a
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negative total and per_month.
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- `loan.on(year, month, day)` - set reception date, month and day are optional, default to Jan 1
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- `loan.repay_monthly(payment, day)` - specify monthly repayments on a given day
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- `loan.begin(year, month)` - set start month for repayments
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