pairs are usable

xexe/processes.py

@@ -11,7 +11,11 @@ from xexe.currency_pair import CurrencyPair
 from xexe.exchange_rates import ExchangeRates, add_equal_rates, add_inverse_rates
 from xexe.rate_fetching import build_rate_fetcher
 from xexe.rate_writing import build_rate_writer
-from xexe.utils import DateRange, generate_currency_and_dates_combinations
+from xexe.utils import (
+    DateRange,
+    generate_currency_and_dates_combinations,
+    generate_pairs_and_dates_combinations,
+)
 
 logger = logging.getLogger()
 
@@ -106,9 +110,15 @@ def obtain_rates_from_source(
         rates_source=rates_source, rate_sources_mapping=RATES_SOURCES
     )
 
-    currency_and_date_combinations = generate_currency_and_dates_combinations(
-        date_range=date_range, currencies=currencies
-    )
+    if currencies:
+        currency_and_date_combinations = generate_currency_and_dates_combinations(
+            date_range=date_range, currencies=currencies
+        )
+
+    if pairs:
+        currency_and_date_combinations = generate_pairs_and_dates_combinations(
+            date_range=date_range, pairs=pairs
+        )
 
     large_api_call_planned = (
         rates_fetcher.is_production_grade and len(currency_and_date_combinations) > 100

xexe/utils.py

@@ -4,6 +4,8 @@ from typing import Set, Tuple
 
 from money.currency import Currency
 
+from xexe.currency_pair import CurrencyPair
+
 
 class DateRange:
 
@@ -86,3 +88,22 @@ def generate_currency_and_dates_combinations(
     currency_date_combinations = tuple(currency_date_combinations)
 
     return currency_date_combinations
+
+
+def generate_pairs_and_dates_combinations(
+    date_range: DateRange, pairs: Set[CurrencyPair]
+) -> Tuple[dict]:
+    currency_date_combinations = []
+    for date in date_range:
+        for pair in pairs:
+            currency_date_combinations.append(
+                {
+                    "from_currency": pair.from_currency,
+                    "to_currency": pair.to_currency,
+                    "date": date,
+                }
+            )
+
+    currency_date_combinations = tuple(currency_date_combinations)
+
+    return currency_date_combinations