def test_calculate_simple_interest(self):
print("test_calculate_simple_interest")
apr = Decimal("48.74")
capital = Decimal("500.00")
et_capital = EntryType.objects.get(code=E_CAPITAL)
entries = [
AccountEntry(type=et_capital,
amount=capital,
timestamp=make_datetime(2017, 1, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 3, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 5, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 7, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 9, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 11, 1)),
AccountEntry(type=et_capital,
amount=Decimal("-437.50"),
timestamp=make_datetime(2018, 1, 1)),
]
timestamp = make_datetime(2018, 1, 1)
interest = calculate_simple_interest(entries, apr, timestamp.date())
print("interest =", dec2(interest))
self.assertEqual(interest.quantize(Decimal("1.00")), Decimal("182.41"))
def test_account(self):
print("test_account")
settlements = create_account_by_type(ACCOUNT_SETTLEMENTS)
assert isinstance(settlements, Account)
amounts = [12, "13.12", "-1.23", "20.00"]
balances = [
Decimal("12.00"),
Decimal("25.12"),
Decimal("23.89"),
Decimal("43.89")
]
t = parse_datetime("2016-06-13T01:00:00")
dt = timedelta(minutes=5)
times = [t + dt * i for i in range(len(amounts))]
for i in range(len(times)):
amount = amounts[i]
t = times[i]
e = AccountEntry(account=settlements,
amount=Decimal(amount),
type=EntryType.objects.get(code=E_SETTLEMENT),
timestamp=t)
e.full_clean()
e.save()
self.assertEqual(settlements.balance, balances[i])
self.assertEqual(settlements.balance, e.balance)
for i in range(len(times)):
t = times[i]
self.assertEqual(settlements.get_balance(t + timedelta(seconds=1)),
balances[i])
def test_calculate_simple_interest2(self):
print('test_calculate_simple_interest2')
apr = Decimal('48.74')
capital = Decimal('500.00')
et_capital = EntryType.objects.get(code=E_CAPITAL)
entries = [
AccountEntry(type=et_capital,
amount=capital,
timestamp=make_datetime(2017, 1, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 3, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 5, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 7, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 9, 1)),
AccountEntry(type=et_capital,
amount=Decimal(-50),
timestamp=make_datetime(2017, 11, 1)),
]
timestamp = make_datetime(2020, 1, 1)
interest = calculate_simple_interest(entries, apr, timestamp.date())
print('interest =', dec2(interest))
self.assertEqual(interest.quantize(Decimal('1.00')), Decimal('426.11'))
def test_calculate_simple_interest3(self):
print("test_calculate_simple_interest3")
apr = Decimal("3.00")
capital = Decimal("500.00")
et_capital = EntryType.objects.get(code=E_CAPITAL)
entries = [
AccountEntry(type=et_capital,
amount=capital,
timestamp=make_datetime(2018, 1, 10)),
]
interest = calculate_simple_interest(entries,
apr,
date(2018, 3, 1),
begin=date(2018, 2, 10))
print("interest =", dec2(interest))
self.assertEqual(interest.quantize(Decimal("1.00")), Decimal("0.78"))
def calculate_simple_interest( # pylint: disable=too-many-locals
entries,
rate_pct: Decimal,
interest_date: Optional[date] = None,
begin: Optional[date] = None,
) -> Decimal:
"""
Calculates simple interest of specified entries over time.
Does not accumulate interest to interest.
:param entries: AccountEntry iterable (e.g. list/QuerySet) ordered by timestamp (ascending)
:param rate_pct: Interest rate %, e.g. 8.00 for 8%
:param interest_date: Interest end date. Default is current date.
:param begin: Optional begin date for the interest. Default is whole range from the timestamp of account entries.
:return: Decimal accumulated interest
"""
if interest_date is None:
interest_date = now().date()
bal = None
cur_date = None
daily_rate = rate_pct / Decimal(36500)
accum_interest = Decimal("0.00")
done = False
entries_list = list(entries)
nentries = len(entries_list)
if nentries > 0:
# make sure we calculate interest over whole range until interest_date
last = entries_list[nentries - 1]
assert isinstance(last, AccountEntry)
if last.timestamp.date() < interest_date:
timestamp = pytz.utc.localize(
datetime.combine(interest_date, time(0, 0)))
e = AccountEntry(timestamp=timestamp,
amount=Decimal("0.00"),
type=last.type)
entries_list.append(e)
# initial values from the first account entry
e = entries_list[0]
bal = e.amount or Decimal("0.00")
cur_date = e.timestamp.date()
if begin and begin > cur_date:
cur_date = begin
for e in entries_list[1:]:
assert isinstance(e, AccountEntry)
next_date = e.timestamp.date()
if begin and begin > next_date:
next_date = begin
if next_date > interest_date:
next_date = interest_date
done = True
assert cur_date
assert bal is not None
time_days = (next_date - cur_date).days
if time_days > 0:
day_interest = bal * daily_rate
interval_interest = day_interest * Decimal(time_days)
accum_interest += interval_interest
cur_date = next_date
if e.amount is not None:
bal += e.amount
if done:
break
return accum_interest