Add python demurrage calculator

python/tests/test_demurrage_ext.py

@@ -0,0 +1,23 @@
+# standard imports
+import datetime
+import unittest
+
+# local imports
+from erc20_demurrage_token.demurrage import DemurrageCalculator
+
+# test imports
+from tests.base import TestDemurrage
+
+
+class TestEmulate(TestDemurrage):
+
+    def test_amount_since(self):
+
+        d = datetime.datetime.utcnow() - datetime.timedelta(seconds=29, hours=5, minutes=3, days=4)
+        c = DemurrageCalculator(0.00000050105908373373)
+        a = c.amount_since(100, d.timestamp())
+        self.assert_within_lower(a, 99.69667, 0.1)
+
+
+if __name__ == '__main__':
+    unittest.main()