refactor the selection on the blt axis out so it can be reused.

pyuvdata/uvdata/miriad.py

@@ -788,8 +788,7 @@ def read_miriad(
             # but that may not matter for many purposes.
             return
 
-        history_update_string = "  Downselected to specific "
-        n_selects = 0
+        selections = []
 
         # select on ant_str if provided
         if ant_str is not None:
@@ -801,8 +800,7 @@ def read_miriad(
 
             aipy_extracts.uv_selector(uv, ant_str)
             if ant_str != "all":
-                history_update_string += "antenna pairs"
-                n_selects += 1
+                selections.append("antenna pairs")
 
         # select on antenna_nums and/or bls using aipy_extracts.uv_selector
         if antenna_nums is not None or bls is not None:
@@ -821,8 +819,7 @@ def read_miriad(
                 # convert antenna numbers to string form required by
                 # aipy_extracts.uv_selector
                 antpair_str_list = ["_".join([str(a) for a in ap]) for ap in antpairs]
-                history_update_string += "antennas"
-                n_selects += 1
+                selections.append("antennas")
 
             if bls is not None:
                 if isinstance(bls, tuple) and (len(bls) == 2 or len(bls) == 3):
@@ -866,7 +863,7 @@ def read_miriad(
                         if len(bl) == 3:
                             bl_pols.add(uvutils.conj_pol(bl[2]))
 
-                if n_selects > 0:
+                if len(selections) > 0:
                     # combine antpair_str_list and bl_str_list with an intersection
                     antpair_str_list = list(
                         set(antpair_str_list).intersection(bl_str_list)
@@ -877,11 +874,7 @@ def read_miriad(
                 if len(bl_pols) > 0:
                     polarizations = list(bl_pols)
 
-                if n_selects > 0:
-                    history_update_string += ", baselines"
-                else:
-                    history_update_string += "baselines"
-                n_selects += 1
+                selections.append("antenna pairs")
 
             # convert antenna pair list to string form required by
             # aipy_extracts.uv_selector
@@ -911,11 +904,8 @@ def read_miriad(
             time_range_use = np.array(time_range) - uv["inttime"] / (24 * 3600.0) / 2
 
             uv.select("time", time_range_use[0], time_range_use[1], include=True)
-            if n_selects > 0:
-                history_update_string += ", times"
-            else:
-                history_update_string += "times"
-            n_selects += 1
+
+            selections.append("times")
 
         # select on polarizations
         if polarizations is not None:
@@ -949,15 +939,15 @@ def read_miriad(
             # check not empty
             if len(pol_list) == 0:
                 raise ValueError("No polarizations in data matched input")
-            if n_selects > 0:
-                history_update_string += ", polarizations"
-            else:
-                history_update_string += "polarizations"
-            n_selects += 1
-
-        history_update_string += " using pyuvdata."
-        if n_selects > 0:
-            self.history += history_update_string
+            selections.append("polarizations")
+
+        if len(selections) > 0:
+            # build up history string from selections
+            self.history += (
+                "  Downselected to specific "
+                + ", ".join(selections)
+                + " using pyuvdata."
+            )
 
         data_accumulator = {}
         pol_list = []

pyuvdata/uvdata/tests/test_uvdata.py

@@ -1481,10 +1481,9 @@ def test_select_phase_center_id_blts(carma_miriad):
     uv_sum = uv1 + uv2 + uv3
     assert uvutils._check_histories(
         uv_obj.history
-        + "  Downselected to specific baseline-times, phase center IDs using pyuvdata. "
+        + "  Downselected to specific phase center IDs, baseline-times using pyuvdata. "
         "Combined data along baseline-time axis using pyuvdata.  "
-        "Combined data along baseline-time axis using pyuvdata.  "
-        "Unique part of next object history follows.  baseline-times",
+        "Combined data along baseline-time axis using pyuvdata.  ",
         uv_sum.history,
     )
     uv_sum.history = uv_obj.history
@@ -1655,7 +1654,7 @@ def test_select_bls(casa_uvfits):
         assert pair in sorted_pairs_to_keep
 
     assert uvutils._check_histories(
-        old_history + "  Downselected to specific baselines using pyuvdata.",
+        old_history + "  Downselected to specific antenna pairs using pyuvdata.",
         uv_object2.history,
     )
 
@@ -1684,7 +1683,7 @@ def test_select_bls(casa_uvfits):
         assert pair in sorted_pairs_to_keep
 
     assert uvutils._check_histories(
-        old_history + "  Downselected to specific baselines using pyuvdata.",
+        old_history + "  Downselected to specific antenna pairs using pyuvdata.",
         uv_object3.history,
     )
 
@@ -1724,7 +1723,7 @@ def test_select_bls(casa_uvfits):
 
     assert uvutils._check_histories(
         old_history
-        + "  Downselected to specific baselines, polarizations using pyuvdata.",
+        + "  Downselected to specific antenna pairs, polarizations using pyuvdata.",
         uv_object2.history,
     )
 
@@ -1752,7 +1751,7 @@ def test_select_bls(casa_uvfits):
         assert pair in sorted_pairs_to_keep
 
     assert uvutils._check_histories(
-        old_history + "  Downselected to specific baselines using pyuvdata.",
+        old_history + "  Downselected to specific antenna pairs using pyuvdata.",
         uv_object2.history,
     )
 
@@ -1791,12 +1790,13 @@ def test_select_bls(casa_uvfits):
 
     with pytest.raises(
         ValueError,
-        match="Cannot provide length-3 tuples and also specify polarizations.",
+        match="Cannot provide any length-3 tuples and also specify polarizations.",
     ):
         uv_object.select(bls=(7, 1, "RR"), polarizations="RR")
 
     with pytest.raises(
-        ValueError, match="The third element in each bl must be a polarization string"
+        ValueError,
+        match="The third element in a bl tuple must be a polarization string",
     ):
         uv_object.select(bls=(7, 1, 7))
 
@@ -2745,7 +2745,7 @@ def test_select(casa_uvfits, future_shapes):
     assert uvutils._check_histories(
         old_history + "  Downselected to "
         "specific baseline-times, antennas, "
-        "baselines, times, frequencies, "
+        "antenna pairs, times, frequencies, "
         "polarizations using pyuvdata.",
         uv_object2.history,
     )
@@ -2853,7 +2853,7 @@ def test_select_with_lst(casa_uvfits, future_shapes):
     assert uvutils._check_histories(
         old_history + "  Downselected to "
         "specific baseline-times, antennas, "
-        "baselines, lsts, frequencies, "
+        "antenna pairs, lsts, frequencies, "
         "polarizations using pyuvdata.",
         uv_object2.history,
     )