Added __eq__ and __hash__ to Period (#207)

Author: mshuffett

pendulum/period.py

@@ -346,3 +346,9 @@ def __reduce__(self):
 
     def __reduce_ex__(self, protocol):
         return self.__class__, self._getstate(protocol)
+
+    def __hash__(self):
+        return hash((self.start, self.end, self._absolute))
+
+    def __eq__(self, other):
+        return (self.start, self.end, self._absolute) == (other.start, other.end, other._absolute)

tests/period/test_hashing.py

@@ -0,0 +1,21 @@
+import pendulum
+
+
+def test_periods_with_same_duration_and_different_dates():
+    day1 = pendulum.DateTime(2018, 1, 1)
+    day2 = pendulum.DateTime(2018, 1, 2)
+    day3 = pendulum.DateTime(2018, 1, 2)
+
+    period1 = day2 - day1
+    period2 = day3 - day2
+
+    assert period1 != period2
+    assert len({period1, period2}) == 2
+
+
+def test_periods_with_same_dates():
+    period1 = pendulum.DateTime(2018, 1, 2) - pendulum.DateTime(2018, 1, 1)
+    period2 = pendulum.DateTime(2018, 1, 2) - pendulum.DateTime(2018, 1, 1)
+
+    assert period1 == period2
+    assert len({period1, period2}) == 1