def test_amortization_amount():
principal = 150000
period = 36
interest_rate = 0.1
amortization = (principal * (interest_rate * (1 + interest_rate)**period) /
((1 + interest_rate)**period - 1))
assert (calculate_amortization_amount(principal, interest_rate,
period) == amortization)
def main(): # pragma: no cover
import argparse
from tabulate import tabulate
parser = argparse.ArgumentParser(
description=
'Python library for calculating amortizations and generating amortization schedules'
)
# required parameters
required = parser.add_argument_group('required arguments')
required.add_argument('-P',
'--principal',
dest='principal',
type=float,
required=True,
help='Principal amount')
required.add_argument('-n',
'--period',
dest='period',
type=int,
required=True,
help='Total number of periods')
required.add_argument('-r',
'--interest-rate',
dest='interest_rate',
type=float,
required=True,
help='Interest rate per period')
# optional parameters
parser.add_argument('-s',
'--schedule',
dest='schedule',
default=False,
action='store_true',
help='Generate amortization schedule')
arguments = parser.parse_args()
if arguments.schedule:
table = (x for x in amortization_schedule(
arguments.principal, arguments.interest_rate, arguments.period))
print(
tabulate(table,
headers=[
"Number", "Amount", "Interest", "Principal", "Balance"
],
floatfmt=",.2f",
numalign="right"))
else:
amount = calculate_amortization_amount(arguments.principal,
arguments.interest_rate,
arguments.period)
print("Amortization amount: {:,.2f}".format(amount))
def amortization_schedule(principal, interest_rate, period):
"""
Generates amortization schedule
:param principal: Principal amount
:param interest_rate: Interest rate per period
:param period: Total number of periods
:return: Rows containing period, interest, principal, balance, etc
"""
amortization_amount = calculate_amortization_amount(
principal, interest_rate, period)
number = 1
balance = principal
while number <= period:
interest = balance * interest_rate
principal = amortization_amount - interest
balance -= principal
yield number, amortization_amount, interest, principal, balance if balance > 0 else 0
number += 1
def amortization_schedule(
principal: float, interest_rate: float,
period: int) -> Iterator[Tuple[int, float, float, float, float]]:
"""
Generates amortization schedule
:param principal: Principal amount
:param interest_rate: Interest rate per period
:param period: Total number of periods
:return: Rows containing period, amount, interest, principal, balance, etc
"""
amortization_amount = calculate_amortization_amount(
principal, interest_rate, period)
adjusted_interest = interest_rate / 12
balance = principal
for number in range(1, period + 1):
interest = round(balance * adjusted_interest, 2)
if number < period:
principal = amortization_amount - interest
balance -= principal
else:
principal, amortization_amount, balance = balance, balance + interest, 0
yield number, amortization_amount, interest, principal, balance
def test_amortization_schedule():
principal = 150000
period = 36
interest_rate = 0.1
amortization_amount = calculate_amortization_amount(
principal, interest_rate, period)
number = 1
balance = principal
for n, a, i, p, b in amortization_schedule(principal, interest_rate,
period):
interest = balance * interest_rate
principal = amortization_amount - interest
balance -= principal
assert number == n
assert amortization_amount == a
assert interest == i
assert principal == p
assert balance == b
number += 1
def _compute_monthly_20(self):
for rec in self:
rec.monthly_20 = calculate_amortization_amount(
rec.loanable_amount, rec.interest_rate / 12, 240)
def main(): # pragma: no cover
import argparse
from tabulate import tabulate
parser = argparse.ArgumentParser(
description=
"Python library for calculating amortizations and generating amortization schedules"
)
# required parameters
required = parser.add_argument_group("required arguments")
required.add_argument(
"-P",
"--principal",
dest="principal",
type=float,
required=True,
help="Principal amount",
)
required.add_argument(
"-n",
"--period",
dest="period",
type=int,
required=True,
help="Total number of periods",
)
required.add_argument(
"-r",
"--interest-rate",
dest="interest_rate",
type=float,
required=True,
help="Interest rate per period",
)
# optional parameters
parser.add_argument(
"-s",
"--schedule",
dest="schedule",
default=False,
action="store_true",
help="Generate amortization schedule",
)
arguments = parser.parse_args()
if arguments.schedule:
table = (x for x in amortization_schedule(
arguments.principal, arguments.interest_rate, arguments.period))
print(
tabulate(
table,
headers=[
"Number", "Amount", "Interest", "Principal", "Balance"
],
floatfmt=",.2f",
numalign="right",
))
else:
amount = calculate_amortization_amount(arguments.principal,
arguments.interest_rate,
arguments.period)
print("Amortization amount: {:,.2f}".format(amount))
def main() -> None: # pragma: no cover
import argparse
from tabulate import tabulate
parser = argparse.ArgumentParser(
description=
"Python library for calculating amortizations and generating amortization schedules"
)
# required parameters
required = parser.add_argument_group("required arguments")
required.add_argument(
"-P",
"--principal",
dest="principal",
type=float,
required=True,
help="Principal amount",
)
required.add_argument(
"-r",
"--interest-rate",
dest="interest_rate",
type=float,
required=True,
help="Interest rate per period",
)
# optional parameters
parser.add_argument(
"-s",
"--schedule",
dest="schedule",
default=False,
action="store_true",
help="Generate amortization schedule",
)
mutually_exclusive = parser.add_mutually_exclusive_group(required=True)
mutually_exclusive.add_argument(
"-n",
"--period",
dest="period",
type=int,
help="Total number of periods",
)
mutually_exclusive.add_argument(
"-a",
"--amount",
dest="amount",
type=float,
help="Amortization amount per period",
)
arguments = parser.parse_args()
if arguments.schedule:
if arguments.period is None:
parser.error("-s/--schedule requires -n/--period")
total_paid = total_interest = total_principal = 0.0
table: List[Any] = []
for row in amortization_schedule(arguments.principal,
arguments.interest_rate,
arguments.period):
table.append(row)
total_paid += row[1]
total_interest += row[2]
total_principal += row[3]
table.append(("Totals", total_paid, total_interest, total_principal))
print(
tabulate(
table,
headers=[
"Number", "Amount", "Interest", "Principal", "Balance"
],
floatfmt=",.2f",
numalign="right",
))
elif arguments.amount:
period = calculate_amortization_period(arguments.principal,
arguments.interest_rate,
arguments.amount)
print("Amortization period: {}".format(period))
else:
amount = calculate_amortization_amount(arguments.principal,
arguments.interest_rate,
arguments.period)
print("Amortization amount: {:,.2f}".format(amount))