Add GncNumeric to native Python Fraction

Add helper method to return the native Python fraction type from GncNumeric.

bindings/python/gnucash_core.py

@@ -320,6 +320,10 @@ def __args_to_instance(args):
         else:
             raise TypeError('Required single int/float/str or two ints: ' + str(args))
 
+    def to_fraction(self):
+        from fractions import Fraction
+        return Fraction(self.num(), self.denom())
+
     def __unicode__(self):
         """Returns a human readable numeric value string as UTF8."""
         return gnc_numeric_to_string(self.instance)

src/optional/python-bindings/tests/test_numeric.py

@@ -79,6 +79,11 @@ def test_to_double(self):
         for test_num in [0.0, 1.1, -1.1, 1/3.0]:
             self.assertEqual(GncNumeric(test_num).to_double(), test_num)
 
+    def test_to_fraction(self):
+        fraction = GncNumeric("1000/3").to_fraction()
+        self.assertEqual(fraction.numerator, 1000)
+        self.assertEqual(fraction.denominator, 3)
+
     def test_incorect_args(self):
         with self.assertRaises(TypeError):
             GncNumeric(1, 2, 3)