CellMethods now printed in CF-compliant manner

docs/src/userguide/interpolation_and_regridding.rst

@@ -75,8 +75,8 @@ Let's take the air temperature cube we've seen previously:
             pressure                    1000.0 hPa
             time                        1998-12-01 00:00:00, bound=(1994-12-01 00:00:00, 1998-12-01 00:00:00)
         Cell methods:
-            mean within years           time
-            mean over years             time
+            time                        mean within years
+            time                        mean over years
         Attributes:
             STASH                       m01s16i203
             source                      Data from Met Office Unified Model
@@ -94,9 +94,9 @@ We can interpolate specific values from the coordinates of the cube:
             pressure                    1000.0 hPa
             time                        1998-12-01 00:00:00, bound=(1994-12-01 00:00:00, 1998-12-01 00:00:00)
         Cell methods:
-            mean within years           time
-            mean over years             time
-        Attributes:
+            time                        mean within years
+            time                        mean over years
+         Attributes:
             STASH                       m01s16i203
             source                      Data from Met Office Unified Model
 

lib/iris/_representation/cube_printout.py

@@ -257,9 +257,12 @@ def add_scalar_row(name, value=""):
                         add_scalar_row(item.name, item.content)
                         if item.extra:
                             add_scalar_row(item_to_extra_indent + item.extra)
-                elif "attribute" in title or "cell method" in title:
+                elif "attribute" in title:
                     for title, value in zip(sect.names, sect.values):
                         add_scalar_row(title, value)
+                elif "cell method" in title:
+                    for title, value in zip(sect.names, sect.values):
+                        add_scalar_row(", ".join(title), value)
                 elif "scalar cell measure" in title:
                     # These are just strings: nothing in the 'value' column.
                     for name in sect.contents:

lib/iris/_representation/cube_summary.py

@@ -222,12 +222,12 @@ def __init__(self, title, cell_methods):
         self.values = []
         self.contents = []
         for method in cell_methods:
-            name = method.method
-            # Remove "method: " from the front of the string, leaving the value.
-            value = str(method)[len(name + ": ") :]
-            self.names.append(name)
+            content = str(method)
+            names = content.split(": ")[:-1]
+            # Remove "coord: " or "coord1: coord2: " from the front of the string, leaving the value.
+            value = content.split(": ")[-1]
+            self.names.append(names)
             self.values.append(value)
-            content = "{}: {}".format(name, value)
             self.contents.append(content)
 
 

lib/iris/coords.py

@@ -2816,25 +2816,24 @@ def __init__(self, method, coords=None, intervals=None, comments=None):
         self._init(method, tuple(_coords), tuple(_intervals), tuple(_comments))
 
     def __str__(self):
-        """Return a custom string representation of CellMethod"""
+        """Return a custom string representation of CellMethod in CF-format"""
         # Group related coord names intervals and comments together
         cell_components = zip_longest(
             self.coord_names, self.intervals, self.comments, fillvalue=""
         )
 
-        collection_summaries = []
-        cm_summary = "%s: " % self.method
+        coords = []
+        other_infos = []
 
         for coord_name, interval, comment in cell_components:
+            coords.append(coord_name)
             other_info = ", ".join(filter(None, chain((interval, comment))))
-            if other_info:
-                coord_summary = "%s (%s)" % (coord_name, other_info)
-            else:
-                coord_summary = "%s" % coord_name
-
-            collection_summaries.append(coord_summary)
+            other_infos.append(other_info)
 
-        return cm_summary + ", ".join(collection_summaries)
+        result = f"{''.join([f'{c}: ' for c in coords])}{self.method}"
+        if any(other_infos):
+            result += f" ({', '.join(other_infos)})"
+        return result
 
     def __add__(self, other):
         # Disable the default tuple behaviour of tuple concatenation

lib/iris/cube.py

@@ -750,9 +750,9 @@ class Cube(CFVariableMixin):
                 time                        \
 1998-12-01 00:00:00, bound=(1994-12-01 00:00:00, 1998-12-01 00:00:00)
             Cell methods:
-                mean within years           time
-                mean over years             time
-            Attributes:
+                time                        mean within years
+                time                        mean over years
+             Attributes:
                 STASH                       m01s16i203
                 source                      Data from Met Office Unified Model
 

lib/iris/tests/results/cdm/str_repr/cell_methods.__str__.txt

@@ -8,10 +8,10 @@ air_temperature / (K)               (latitude: 73; longitude: 96)
         pressure                    1000.0 hPa
         time                        1998-12-01 00:00:00
     Cell methods:
-        mean                        longitude (6 minutes, This is a test comment), latitude (12 minutes)
-        average                     longitude (6 minutes, This is another test comment), latitude (15 minutes, This is another comment)
-        average                     longitude, latitude
-        percentile                  longitude (6 minutes, This is another test comment)
+        longitude, latitude         mean (6 minutes, This is a test comment, 12 minutes)
+        longitude, latitude         average (6 minutes, This is another test comment, 15 minutes, This is another comment)
+        longitude, latitude         average
+        longitude                   percentile (6 minutes, This is another test comment)
     Attributes:
         STASH                       m01s16i203
         source                      Data from Met Office Unified Model

lib/iris/tests/unit/coords/test_CellMethod.py

@@ -22,7 +22,7 @@ def setUp(self):
     def _check(self, token, coord, default=False):
         result = CellMethod(self.method, coords=coord)
         token = token if not default else BaseMetadata.DEFAULT_NAME
-        expected = "{}: {}".format(self.method, token)
+        expected = "{}: {}".format(token, self.method)
         self.assertEqual(str(result), expected)
 
     def test_coord_standard_name(self):
@@ -64,27 +64,27 @@ def test_coord_stash_default(self):
     def test_string(self):
         token = "air_temperature"
         result = CellMethod(self.method, coords=token)
-        expected = "{}: {}".format(self.method, token)
+        expected = "{}: {}".format(token, self.method)
         self.assertEqual(str(result), expected)
 
     def test_string_default(self):
         token = "air temperature"  # includes space
         result = CellMethod(self.method, coords=token)
-        expected = "{}: unknown".format(self.method)
+        expected = "unknown: {}".format(self.method)
         self.assertEqual(str(result), expected)
 
     def test_mixture(self):
         token = "air_temperature"
         coord = AuxCoord(1, standard_name=token)
         result = CellMethod(self.method, coords=[coord, token])
-        expected = "{}: {}, {}".format(self.method, token, token)
+        expected = "{0}: {0}: {1}".format(token, self.method)
         self.assertEqual(str(result), expected)
 
     def test_mixture_default(self):
         token = "air temperature"  # includes space
         coord = AuxCoord(1, long_name=token)
         result = CellMethod(self.method, coords=[coord, token])
-        expected = "{}: unknown, unknown".format(self.method)
+        expected = "unknown: unknown: {}".format(self.method)
         self.assertEqual(str(result), expected)
 
 

lib/iris/tests/unit/experimental/representation/test_CubeRepresentation.py

@@ -198,9 +198,12 @@ def test_headings__cellmethods(self):
         contents = self.representer.str_headings["Cell methods:"]
         content_str = ",".join(content for content in contents)
         for method in self.cube.cell_methods:
-            name = method.method
-            value = str(method)[len(name + ": ") :]
-            self.assertIn(name, content_str)
+            content = str(method)
+            names = content.split(":")[:-1]
+            # Remove "coord: " or "coord1: coord2: " from the front of the string, leaving the value.
+            value = content.split(":")[-1][1:]
+            for name in names:
+                self.assertIn(name, content_str)
             self.assertIn(value, content_str)
 
 

lib/iris/tests/unit/representation/cube_printout/test_CubePrintout.py

@@ -508,8 +508,8 @@ def test_section_cell_methods(self):
         expected = [
             "name / (1)                          (-- : 1)",
             "    Cell methods:",
-            "        stdev                       area",
-            "        mean                        y (10m, vertical), time (3min, =duration)",
+            "        area                        stdev",
+            "        y, time                     mean (10m, vertical, 3min, =duration)",
         ]
         self.assertEqual(rep, expected)
 

lib/iris/tests/unit/representation/cube_summary/test_CubeSummary.py

@@ -198,7 +198,7 @@ def test_cell_methods(self):
 
         rep = CubeSummary(cube)
         cell_method_section = rep.scalar_sections["Cell methods:"]
-        expected_contents = ["mean: x, y", "mean: x"]
+        expected_contents = ["x: y: mean", "x: mean"]
         self.assertEqual(cell_method_section.contents, expected_contents)
 
     def test_scalar_cube(self):