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https://github.com/spiral-project/ihatemoney.git
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Merge 23d5b73ae1 into 56bee93346
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gr4viton
GitHub
commit
8b5df5d336
1 changed files with 85 additions and 188 deletions
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@ -1,10 +1,17 @@
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import csv
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import traceback
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import warnings
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from abc import ABC, abstractmethod
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from decimal import Decimal
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from typing import Dict, Optional
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from cachetools import TTLCache, cached
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import requests
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NO_CURRENCY = "XXX"
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ExchangeRates = Dict[str, float]
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class Singleton(type):
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_instances = {}
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@ -14,205 +21,93 @@ class Singleton(type):
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return cls._instances[cls]
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class CurrencyConverter(object, metaclass=Singleton):
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# Get exchange rates
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no_currency = "XXX"
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class ExchangeRateGetter(ABC):
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def get_rates(self) -> Optional[ExchangeRates]:
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"""Method to retrieve a list of currency conversion rates.
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Returns:
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currencies: dict - key is a three-letter currency, value is float of conversion to base currency
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"""
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try:
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return self._get_rates()
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except Exception:
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warnings.warn(
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f"Exchange rate getter failed - {traceback.format_exc(limit=0).strip()}"
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)
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@abstractmethod
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def _get_rates(self) -> Optional[ExchangeRates]:
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"""Actual implementation of the exchange rate getter."""
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raise NotImplementedError
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class ApiExchangeRate(ExchangeRateGetter):
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api_url = "https://api.exchangerate.host/latest?base=USD"
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def _get_rates(self) -> Optional[ExchangeRates]:
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return requests.get(self.api_url).json()["rates"] # TODO not working currently probably
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class UserExchangeRate(ExchangeRateGetter):
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user_csv_file = "path/to/file.csv"
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def _get_rates(self) -> Optional[ExchangeRates]:
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"""Get rates from user defined csv.
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The user_csv_file should contain the currency conversions to "USD" without 1 header row
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Example:
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```
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currency_code,fx_rate_to_USD
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CZK,25.0
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...
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```
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TODO: make it work bi-directionally
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TODO: document for the user where to place the file
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"""
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reader = csv.reader(self.user_csv_file)
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rates = {}
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for row in reader:
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from_currency = row[0]
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rate = float(row[1])
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# TODO add validation and exception handling for typos
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rates[from_currency] = rate
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return rates
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class HardCodedExchangeRate(ExchangeRateGetter):
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def _get_rates(self) -> Optional[dict]:
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return {"USD": 1.0} # TODO fill in more
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class CurrencyConverter(object, metaclass=Singleton):
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no_currency = NO_CURRENCY
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def __init__(self):
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pass
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@cached(cache=TTLCache(maxsize=1, ttl=86400))
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def get_rates(self):
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try:
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rates = requests.get(self.api_url).json()["rates"]
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except Exception:
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warnings.warn(
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f"Call to {self.api_url} failed: {traceback.format_exc(limit=0).strip()}"
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)
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# In case of any exception, let's have an empty value
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"""Try to retrieve the exchange rate from various sources, defaulting to hard coded values."""
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for provider in [ApiExchangeRate, UserExchangeRate, HardCodedExchangeRate]:
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if rates:= provider.get_rates():
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break
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else:
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rates = {}
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rates[self.no_currency] = 1.0
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rates[NO_CURRENCY] = 1.0
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return rates
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def get_currencies(self, with_no_currency=True):
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currencies = [
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"AED",
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"AFN",
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"ALL",
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"AMD",
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"ANG",
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"AOA",
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"ARS",
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"AUD",
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"AWG",
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"AZN",
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"BAM",
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"BBD",
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"BDT",
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"BGN",
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"BHD",
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"BIF",
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"BMD",
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"BND",
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"BOB",
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"BRL",
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"BSD",
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"BTC",
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"BTN",
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"BWP",
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"BYN",
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"BZD",
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"CAD",
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"CDF",
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"CHF",
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"CLF",
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"CLP",
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"CNH",
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"CNY",
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"COP",
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"CRC",
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"CUC",
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"CUP",
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"CVE",
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"CZK",
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"DJF",
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"DKK",
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"DOP",
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"DZD",
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"EGP",
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"ERN",
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"ETB",
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"EUR",
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"FJD",
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"FKP",
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"GBP",
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"GEL",
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"GGP",
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"GHS",
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"GIP",
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"GMD",
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"GNF",
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"GTQ",
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"GYD",
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"HKD",
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"HNL",
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"HRK",
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"HTG",
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"HUF",
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"IDR",
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"ILS",
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"IMP",
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"INR",
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"IQD",
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"IRR",
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"ISK",
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"JEP",
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"JMD",
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"JOD",
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"JPY",
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"KES",
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"KGS",
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"KHR",
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"KMF",
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"KPW",
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"KRW",
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"KWD",
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"KYD",
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"KZT",
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"LAK",
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"LBP",
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"LKR",
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"LRD",
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"LSL",
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"LYD",
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"MAD",
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"MDL",
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"MGA",
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"MKD",
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"MMK",
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"MNT",
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"MOP",
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"MRU",
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"MUR",
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"MVR",
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"MWK",
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"MXN",
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"MYR",
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"MZN",
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"NAD",
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"NGN",
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"NIO",
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"NOK",
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"NPR",
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"NZD",
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"OMR",
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"PAB",
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"PEN",
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"PGK",
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"PHP",
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"PKR",
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"PLN",
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"PYG",
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"QAR",
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"RON",
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"RSD",
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"RUB",
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"RWF",
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"SAR",
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"SBD",
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"SCR",
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"SDG",
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"SEK",
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"SGD",
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"SHP",
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"SLL",
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"SOS",
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"SRD",
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"SSP",
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"STD",
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"STN",
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"SVC",
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"SYP",
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"SZL",
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"THB",
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"TJS",
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"TMT",
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"TND",
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"TOP",
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"TRY",
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"TTD",
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"TWD",
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"TZS",
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"UAH",
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"UGX",
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"USD",
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"UYU",
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"UZS",
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"VEF",
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"VES",
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"VND",
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"VUV",
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"WST",
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"XAF",
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"XAG",
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"XAU",
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"XCD",
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"XDR",
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"XOF",
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"XPD",
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"XPF",
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"XPT",
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"YER",
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"ZAR",
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"ZMW",
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"ZWL",
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]
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def get_currencies(self, with_no_currency: bool=True) -> list:
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currencies = list(self.get_rates.keys())
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if with_no_currency:
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currencies.append(self.no_currency)
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return currencies
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def exchange_currency(self, amount, source_currency, dest_currency):
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def exchange_currency(self, amount: float, source_currency: str, dest_currency: str) -> float:
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"""Return the money amount converted from source_currency to dest_currency."""
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if (
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source_currency == dest_currency
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or source_currency == self.no_currency
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@ -223,6 +118,8 @@ class CurrencyConverter(object, metaclass=Singleton):
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rates = self.get_rates()
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source_rate = rates[source_currency]
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dest_rate = rates[dest_currency]
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new_amount = (float(amount) / source_rate) * dest_rate
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# round to two digits because we are dealing with money
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return round(new_amount, 2)
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# Using Decimal to not introduce floating-point operation absolute errors
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new_amount = (Decimal(amount) / Decimal(source_rate)) * Decimal(dest_rate)
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# dealing with money - only round the shown amount before showing it to user
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# - think about 10 * 0.0003 == 0?
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return float(new_amount)
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