reports: Add Balance.__abs__() method.

conservancy_beancount/reports/core.py

@@ -21,6 +21,8 @@ from decimal import Decimal
 
 import babel.numbers  # type:ignore[import]
 
+from beancount.core import amount as bc_amount
+
 from .. import data
 
 from typing import (
@@ -73,6 +75,11 @@ class Balance(Mapping[str, data.Amount]):
     def __str__(self) -> str:
         return self.format()
 
+    def __abs__(self) -> 'Balance':
+        return type(self)(
+            (key, bc_amount.abs(amt)) for key, amt in self.items()
+        )
+
     def __eq__(self, other: Any) -> bool:
         if (self.is_zero()
             and isinstance(other, Balance)

tests/test_reports_balance.py

@@ -127,6 +127,25 @@ def test_le_zero(balance_map_kwargs, expected):
     balance = core.Balance(amounts.items())
     assert balance.le_zero() == expected
 
+@pytest.mark.parametrize('balance_map_kwargs', [
+    {},
+    {'USD': 0},
+    {'EUR': 10},
+    {'JPY': 20, 'BRL': 30},
+    {'EUR': -15},
+    {'JPY': -25, 'BRL': -35},
+    {'JPY': 40, 'USD': 0, 'EUR': -50},
+])
+def test_abs(balance_map_kwargs):
+    amounts = testutil.balance_map(**balance_map_kwargs)
+    actual = abs(core.Balance(amounts.items()))
+    assert set(actual) == set(balance_map_kwargs)
+    abs_amounts = testutil.balance_map(**{
+        key: abs(number) for key, number in balance_map_kwargs.items()
+    })
+    for key in balance_map_kwargs:
+        assert actual[key] == abs_amounts[key]
+
 @pytest.mark.parametrize('balance_map_kwargs', [
     {},
     {'USD': 0},