rewrote set_interval, and added test where same interval set twice in…

… a row. Closes #222

tests/test_traces.py

@@ -123,6 +123,9 @@ def test_set_interval():
     tsd = TimeSeries()
     pytest.raises(ValueError, tsd.set_interval, 4, 4, 4)
 
+    tsd = TimeSeries()
+    pytest.raises(ValueError, tsd.set_interval, 4, 3, 4)
+
 
 def test_set_interval_datetime():
     ts = TimeSeries(default=400)
@@ -231,3 +234,13 @@ def value_parse(value):
     assert ts[datetime(2000, 1, 1, 9)] is None
     assert ts[datetime(2000, 1, 1, 10, 30)] == "15"
     assert ts[datetime(2000, 1, 1, 20)] == "nan"
+
+
+def test_set_same_interval_twice():
+    tr = TimeSeries({0: 10, 100: 10})
+
+    tr[17:42] = 0
+    assert list(tr.items()) == [(0, 10), (17, 0), (42, 10), (100, 10)]
+
+    tr[17:42] = 0
+    assert list(tr.items()) == [(0, 10), (17, 0), (42, 10), (100, 10)]

traces/timeseries.py

@@ -180,19 +180,18 @@ def set_interval(self, start, end, value, compact=False):
         be anyway.
 
         """
-        # for each interval to render
-        for i, (s, _e, v) in enumerate(list(self.iterperiods(start, end))):  # noqa: B007
-            # look at all intervals included in the current interval
-            # (always at least 1)
-            if i == 0:
-                # if the first, set initial value to new value of range
-                self.set(s, value, compact)
-            else:
-                # otherwise, remove intermediate key
-                del self[s]
+        if start >= end:
+            msg = f"start must be less than end, got start={start!r} and end={end!r}"
+            raise ValueError(msg)
+
+        end_value = self[end]
+
+        # delete all intermediate items between start and end
+        for t in list(self._d.irange(start, end, inclusive=(False, False))):
+            del self[t]
 
-        # finish by setting the end of the interval to the previous value
-        self.set(end, v, compact)
+        self.set(start, value, compact)
+        self.set(end, end_value, compact)
 
     def compact(self):
         """Convert this instance to a compact version: the value will be the