Oh, forgot renamed currency.py. :/

piggybank/currency.py

@@ -0,0 +1,128 @@
+"""Currency class and a set of exceptions.
+
+Face values are stored as decimals*.
+
+* Decimal is used to avoid problems of rounding float numbers. So first two
+digits to the right are used to store a fraction part. You can simply divide
+this number by 100 to get a floating-point number.
+
+Currency string has following format:
+    <ISO>;<CURRENCY NAME>;<COINS COUNT>;{}<FRACTION SYMBOL>,{}<CURRENCY SYMBOL>
+    ;<FACE VALUES>
+
+{} with currency symbol used as a placeholder for where to put digits.
+
+Example:
+    RUB;Russian ruble;8;{}коп.,{}₽;1,5,10,50,100,200,500,1000
+    USD;US Dollar;6;{}¢,${};1,5,10,25,50,100
+"""
+
+from __future__ import annotations
+from operator import mul
+from typing import Dict, List, TypedDict
+
+__all__ = [ "Currency", "BaseCurrencyError", "CurrencyIsNotSupportedError",
+            "CurrenciesCoinCountMismatchError", "CurrencyMismatchError"]
+
+
+class BaseCurrencyError(Exception):
+    """Base class for all currency exeptions."""
+    def __init__(self, message=None, *args, **kwargs) -> None:
+        if message is None:
+            message = self.__doc__
+        super().__init__(message, *args, **kwargs)
+
+
+class CurrencyIsNotSupportedError(BaseCurrencyError):
+    """Currency is not supported."""
+
+
+class CurrencyMismatchError(BaseCurrencyError):
+    """Currencies doesn't match, but they must do so."""
+    def __init__(self, extra=None):
+        if not extra is None:
+            super().__init__(f"{self.__doc__} {extra}")
+        else:
+            super().__init__(self.__doc__)
+
+
+class CurrenciesCoinCountMismatchError(BaseCurrencyError):
+    """Length of list supplied doesn't corresponds coins count."""
+
+
+class Currency:
+    """Currency's representation and methods to work with it.
+
+    Arguments:
+        iso_code        -- ISO code of a currency;
+        name            -- full name of a currency;
+        coins_count     -- number of face values of coins;
+        fraction_symbol -- a symbol or word for a fraction of currency (e.g. c, cent);
+        currency_symbol -- a symbol or word for a currency (e.g. $);
+        face_values     -- list of values for each face value in decimal
+                           (e.g. $476.40 is 47640);
+    """
+    def __init__(self, iso_code: str, name: str, coins_count: int,
+                 fraction_symbol: str, currency_symbol: str,
+                 face_values: List[int]):
+        self._iso = iso_code.upper()
+        self._name = name
+        self._coins_count = coins_count
+        self._fraction_symbol = fraction_symbol
+        self._currency_symbol = currency_symbol
+        self._face_values = face_values
+
+    @property
+    def iso(self) -> str:
+        """ISO code of a currency."""
+        return self._iso
+
+    @property
+    def name(self) -> str:
+        """Full name of a currency."""
+        return self._name
+
+    @property
+    def count(self):
+        """Count of coins of a currency."""
+        return self._coins_count
+
+    @property
+    def fraction_symbol(self) -> str:
+        """Returns a symbol or word for a fraction of a currency."""
+        return self._fraction_symbol
+
+    @property
+    def currency_symbol(self) -> str:
+        """Returns a symbol or word for a currency."""
+        return self._currency_symbol
+
+    @property
+    def face_values(self) -> List[int]:
+        """Face values of coins. From least to most."""
+        return self._face_values
+
+    def multiply(self, lst: List[int]) -> List[float]:
+        """Multiplies a list by face values. Length of list must match
+        currency's coins count."""
+        if len(lst) != len(self):
+            raise CurrenciesCoinCountMismatchError
+        return list(map(mul, lst, self.face_values))
+
+    @staticmethod
+    def from_string(currency: str) -> Currency:
+        """Creates a Currency object from its string representation."""
+        iso, name, count, frac_sym, cur_sym, fv = currency.split(";")
+        return Currency(iso, name, int(count), frac_sym, cur_sym,
+                        list(map(int, fv.split(","))))
+
+    def __mul__(self, lst: List[int]) -> List[float]:
+        return self.multiply(lst)
+
+    def __len__(self) -> int:
+        return self.count
+
+    def __str__(self):
+        return f"{self.iso};{self.name};{self.count};" \
+               f"{self.fraction_symbol},{self.currency_symbol};" \
+               f"{','.join(list(map(str, self.face_values)))}"