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#!/usr/bin/env python3
from decimal import Decimal
import re
from typing import Optional, TypeVar, Tuple
import math_utils
T = TypeVar('T', bound='Money')
class Money(object):
"""A class for representing monetary amounts potentially with
different currencies.
"""
def __init__ (
self,
amount: Decimal = Decimal("0.0"),
currency: str = 'USD',
*,
strict_mode = False
):
self.strict_mode = strict_mode
if isinstance(amount, str):
ret = Money._parse(amount)
if ret is None:
raise Exception(f'Unable to parse money string "{amount}"')
amount = ret[0]
currency = ret[1]
if not isinstance(amount, Decimal):
amount = Decimal(float(amount))
self.amount = amount
if not currency:
self.currency: Optional[str] = None
else:
self.currency: Optional[str] = currency
def __repr__(self):
a = float(self.amount)
a = round(a, 2)
s = f'{a:,.2f}'
if self.currency is not None:
return '%s %s' % (s, self.currency)
else:
return '$%s' % s
def __pos__(self):
return Money(amount=self.amount, currency=self.currency)
def __neg__(self):
return Money(amount=-self.amount, currency=self.currency)
def __add__(self, other):
if isinstance(other, Money):
if self.currency == other.currency:
return Money(
amount = self.amount + other.amount,
currency = self.currency
)
else:
raise TypeError('Incompatible currencies in add expression')
else:
if self.strict_mode:
raise TypeError('In strict_mode only two moneys can be added')
else:
return Money(
amount = self.amount + Decimal(float(other)),
currency = self.currency
)
def __sub__(self, other):
if isinstance(other, Money):
if self.currency == other.currency:
return Money(
amount = self.amount - other.amount,
currency = self.currency
)
else:
raise TypeError('Incompatible currencies in add expression')
else:
if self.strict_mode:
raise TypeError('In strict_mode only two moneys can be added')
else:
return Money(
amount = self.amount - Decimal(float(other)),
currency = self.currency
)
def __mul__(self, other):
if isinstance(other, Money):
raise TypeError('can not multiply monetary quantities')
else:
return Money(
amount = self.amount * Decimal(float(other)),
currency = self.currency
)
def __truediv__(self, other):
if isinstance(other, Money):
raise TypeError('can not divide monetary quantities')
else:
return Money(
amount = self.amount / Decimal(float(other)),
currency = self.currency
)
def __float__(self):
return self.amount.__float__()
def truncate_fractional_cents(self):
x = float(self)
self.amount = Decimal(math_utils.truncate_float(x))
return self.amount
def round_fractional_cents(self):
x = float(self)
self.amount = Decimal(round(x, 2))
return self.amount
__radd__ = __add__
def __rsub__(self, other):
if isinstance(other, Money):
if self.currency == other.currency:
return Money(
amount = other.amount - self.amount,
currency = self.currency
)
else:
raise TypeError('Incompatible currencies in sub expression')
else:
if self.strict_mode:
raise TypeError('In strict_mode only two moneys can be added')
else:
return Money(
amount = Decimal(float(other)) - self.amount,
currency = self.currency
)
__rmul__ = __mul__
#
# Override comparison operators to also compare currency.
#
def __eq__(self, other):
if other is None:
return False
if isinstance(other, Money):
return (
self.amount == other.amount and
self.currency == other.currency
)
if self.strict_mode:
raise TypeError("In strict mode only two Moneys can be compared")
else:
return self.amount == Decimal(float(other))
def __ne__(self, other):
result = self.__eq__(other)
if result is NotImplemented:
return result
return not result
def __lt__(self, other):
if isinstance(other, Money):
if self.currency == other.currency:
return self.amount < other.amount
else:
raise TypeError('can not directly compare different currencies')
else:
if self.strict_mode:
raise TypeError('In strict mode, only two Moneys can be compated')
else:
return self.amount < Decimal(float(other))
def __gt__(self, other):
if isinstance(other, Money):
if self.currency == other.currency:
return self.amount > other.amount
else:
raise TypeError('can not directly compare different currencies')
else:
if self.strict_mode:
raise TypeError('In strict mode, only two Moneys can be compated')
else:
return self.amount > Decimal(float(other))
def __le__(self, other):
return self < other or self == other
def __ge__(self, other):
return self > other or self == other
def __hash__(self):
return self.__repr__
AMOUNT_RE = re.compile("^([+|-]?)(\d+)(\.\d+)$")
CURRENCY_RE = re.compile("^[A-Z][A-Z][A-Z]$")
@classmethod
def _parse(cls, s: str) -> Optional[Tuple[Decimal, str]]:
amount = None
currency = None
s = s.strip()
chunks = s.split(' ')
try:
for chunk in chunks:
if Money.AMOUNT_RE.match(chunk) is not None:
amount = Decimal(chunk)
elif Money.CURRENCY_RE.match(chunk) is not None:
currency = chunk
except:
pass
if amount is not None and currency is not None:
return (amount, currency)
elif amount is not None:
return (amount, 'USD')
return None
@classmethod
def parse(cls, s: str) -> T:
chunks = Money._parse(s)
if chunks is not None:
return Money(chunks[0], chunks[1])
raise Exception(f'Unable to parse money string "{s}"')
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