Second batch of @orbeckst comments

package/MDAnalysis/coordinates/base.py

@@ -1528,7 +1528,7 @@ def __getitem__(self, frame):
             frame = self._apply_limits(frame)
             return self._read_frame_with_aux(frame)
         elif isinstance(frame, (list, np.ndarray)):
-            if isinstance(frame[0], (bool, np.bool_)):
+            if len(frame) != 0 and isinstance(frame[0], (bool, np.bool_)):
                 # Avoid having list of bools
                 frame = np.asarray(frame, dtype=np.bool)
                 # Convert bool array to int array

package/MDAnalysis/core/groups.py

@@ -2546,7 +2546,7 @@ def write(self, filename=None, file_format="PDB",
         >>> # Write the trajectory in XTC format
         >>> ag.write('trajectory.xtc', frames='all')
         >>> # Write every other frame of the trajectory in PBD format
-        >>> ag.abswrite('trajectory.pdb', frames=u.trajectory[::2]
+        >>> ag.write('trajectory.pdb', frames=u.trajectory[::2])
 
         Parameters
         ----------
@@ -2565,19 +2565,22 @@ def write(self, filename=None, file_format="PDB",
             file. ``"all"``: write out all bonds, both the original defined and
             those guessed by MDAnalysis. ``None``: do not write out bonds.
             Default is ``"conect"``.
-        frames:
+        frames: array-like or slice or FrameIteratorBase or str, optional
             An ensemble of frames to write. The ensemble can be an list or
             array of frame indices, a mask of booleans, an instance of
             :class:`slice`, or the value returned when a trajectory is indexed.
-            By default, 'frames' is set to ``None`` and only the current frame
-            is written.
+            By default, `frames` is set to ``None`` and only the current frame
+            is written. If `frames` is set to "all", then all the frame from
+            trajectory are written.
 
 
         .. versionchanged:: 0.9.0 Merged with write_selection. This method can
             now write both selections out.
         .. versionchanged:: 0.19.0
             Can write multiframe trajectories with the 'frames' argument.
         """
+        # TODO: Add a 'verbose' option alongside 'frames'.
+
         # check that AtomGroup actually has any atoms (Issue #434)
         if len(self.atoms) == 0:
             raise IndexError("Cannot write an AtomGroup with 0 atoms")
@@ -2647,8 +2650,12 @@ def write(self, filename=None, file_format="PDB",
                 if frames is None:
                     w.write(self.atoms)
                 else:
-                    for _ in trj_frames:
-                        w.write(self.atoms)
+                    current_frame = trj.ts.frame
+                    try:
+                        for _ in trj_frames:
+                            w.write(self.atoms)
+                    finally:
+                        trj[current_frame]
             return
 
         try:

testsuite/MDAnalysisTests/coordinates/test_reader_api.py

@@ -170,7 +170,9 @@ class TestMultiFrameReader(_Multi):
         (1, 5, -1),  # Stop less than start
         (-100, None, None),
         (100, None, None),  # Outside of range of trajectory
-        (-2, 10, -2)
+        (-2, 10, -2),
+        (0, 0, 1),  # empty
+        (10, 1, 2), # empty
     ])
     def test_slice(self, start, stop, step, reader):
         """Compare the slice applied to trajectory, to slice of list"""
@@ -226,6 +228,8 @@ def test_getitem(self, slice_cls, sl, reader):
         slice(10, 0, -1),
         slice(2, 7, 2),
         slice(7, 2, -2),
+        slice(7, 2, 1),  # empty
+        slice(0, 0, 1),  # empty
     ])
     def test_getitem_len(self, sl, reader):
         traj_iterable = reader[sl]
@@ -234,6 +238,12 @@ def test_getitem_len(self, sl, reader):
         ref = self.reference[sl]
         assert len(traj_iterable) == len(ref)
 
+    @pytest.mark.parametrize('iter_type', (list, np.array))
+    def test_getitem_len_empty(self, reader, iter_type):
+        # Indexing a numpy array with an empty array tends to break.
+        traj_iterable = reader[iter_type([])]
+        assert len(traj_iterable) == 0
+
     # All the sl1 slice must be 5 frames long so that the sl2 can be a mask
     @pytest.mark.parametrize('sl1', [
         [0, 1, 2, 3, 4],

testsuite/MDAnalysisTests/core/test_atomgroup.py

@@ -191,6 +191,13 @@ def test_incompatible_trajectories(self, tmpdir):
         with pytest.raises(ValueError):
             u1.atoms.write(destination, frames=u2.trajectory)
 
+    def test_write_no_traj_move(self, u, tmpdir):
+        destination = str(tmpdir / 'test.dcd')
+        u.trajectory[10]
+        u.atoms.write(destination, frames=[1, 2, 3])
+        assert u.trajectory.ts.frame == 10
+
+
     def test_write_selection(self, u, tmpdir):
         with tmpdir.as_cwd():
             u.atoms.write("test.vmd")