Add deprecation warning for memoryreader inclusive indexing in timeseries.

package/CHANGELOG

@@ -62,6 +62,8 @@ Changes
   * adding element attribute to TXYZParser if all atom names are valid element symbols (PR #3826)
 
 Deprecations
+  * Add deprecation warning for inclusive start, stop, step indexing
+    in MemoryReader.timeseries (#PR 3894)  
 
 
 08/29/22 IAlibay, PicoCentauri, orbeckst, hmacdope, rmeli, miss77jun, rzhao271,

package/MDAnalysis/coordinates/memory.py

@@ -502,8 +502,12 @@ def timeseries(self, asel=None, start=0, stop=-1, step=1, order='afc'):
             data is returned whenever `asel` is different from ``None``.
         start : int (optional)
         stop : int (optional)
+            Note that `stop` is currently *inclusive* but will be deprecated in
+            favour of being *exclusive* in 3.0.  
         step : int (optional)
-            range of trajectory to access, `start` and `stop` are *inclusive*
+            range of trajectory to access, `start` and `stop` are
+            currently *inclusive* but will be changed to be *exclusive* in
+            3.0.
         order : {"afc", "acf", "caf", "fac", "fca", "cfa"} (optional)
             the order/shape of the return data array, corresponding
             to (a)tom, (f)rame, (c)oordinates all six combinations
@@ -514,7 +518,14 @@ def timeseries(self, asel=None, start=0, stop=-1, step=1, order='afc'):
 
         .. versionchanged:: 1.0.0
            Deprecated `format` keyword has been removed. Use `order` instead.
+        .. versionchanged:: 2.4.0
+           Deprecation warning 
         """
+        if stop != -1:
+            warnings.warn("MemoryReader.timeseries inclusive `start` and `stop`"
+                      " indexing will be removed in 3.0 in favour of exclusive "
+                      "indexing",category=DeprecationWarning)
+
         array = self.get_array()
         if order == self.stored_order:
             pass

testsuite/MDAnalysisTests/coordinates/test_memory.py

@@ -197,6 +197,11 @@ def test_position_assignation(self, reader):
         reader[0]
         assert_almost_equal(reader.ts.positions, new_positions)
 
+    def test_timeseries_warns_deprecation(self, reader):
+        with pytest.warns(DeprecationWarning, match="MemoryReader.timeseries "
+                          "inclusive"):
+            reader.timeseries(start=0, stop=3, step=1)
+
 
 class TestMemoryReaderVelsForces(object):
     @staticmethod