List "Unindexed dimensions" separately in __repr__ (#1221)

Fixes GH1199

Previously (on master):

    <xarray.Dataset>
    Dimensions:  (x: 1, y: 2)
    Coordinates:
      o x        (x) -
      o y        (y) -
    Data variables:
        foo      (x, y) int64 1 2

Now:

    <xarray.Dataset>
    Dimensions:  (x: 1, y: 2)
    Coordinates:
        *empty*
    Unindexed dimensions:
        x, y
    Data variables:
        foo      (x, y) int64 1 2

This version of the `__repr__` should be much more self-explanatory.

Author: shoyer

doc/data-structures.rst

@@ -48,7 +48,7 @@ The :py:class:`~xarray.DataArray` constructor takes:
   :py:class:`~pandas.Series`, :py:class:`~pandas.DataFrame` or :py:class:`~pandas.Panel`)
 - ``coords``: a list or dictionary of coordinates
 - ``dims``: a list of dimension names. If omitted, dimension names are
-  taken from ``coords`` if possible
+  taken from ``coords`` if possible.
 - ``attrs``: a dictionary of attributes to add to the instance
 - ``name``: a string that names the instance
 
@@ -69,15 +69,19 @@ in with default values:
 
 As you can see, dimension names are always present in the xarray data model: if
 you do not provide them, defaults of the form ``dim_N`` will be created.
+However, coordinates are optional. If you do not specific coordinates for a
+dimension, the axis name will appear under the list of "Unindexed dimensions".
 
 .. note::
 
-  Prior to xarray v0.9, coordinates corresponding to dimension were *also*
-  always present in xarray: xarray would create default coordinates of the form
-  ``range(dim_size)`` if coordinates were not supplied explicitly. This is no
-  longer the case.
+  This is different from pandas, where axes always have tick labels, which
+  default to the integers ``[0, ..., n-1]``.
 
-Coordinates can take the following forms:
+  Prior to xarray v0.9, xarray copied this behavior: default coordinates for
+  each dimension would be created if coordinates were not supplied explicitly.
+  This is no longer the case.
+
+Coordinates can be specified in the following ways:
 
 - A list of values with length equal to the number of dimensions, providing
   coordinate labels for each dimension. Each value must be of one of the
@@ -243,8 +247,8 @@ Creating a Dataset
 To make an :py:class:`~xarray.Dataset` from scratch, supply dictionaries for any
 variables (``data_vars``), coordinates (``coords``) and attributes (``attrs``).
 
-- ``data_vars`` should be a dictionary with each key as the name of the variable and each
-value as one of:
+- ``data_vars`` should be a dictionary with each key as the name of the variable
+  and each value as one of:
 
   * A :py:class:`~xarray.DataArray` or :py:class:`~xarray.Variable`
   * A tuple of the form ``(dims, data[, attrs])``, which is converted into

doc/whats-new.rst

@@ -31,7 +31,25 @@ Breaking changes
 ~~~~~~~~~~~~~~~~
 
 - Index coordinates for each dimensions are now optional, and no longer created
-  by default :issue:`1017`. This has a number of implications:
+  by default :issue:`1017`. You can identify such dimensions without indexes by
+  their appearance in list of "Unindexed dimensions" in the ``Dataset`` or
+  ``DataArray`` repr:
+
+  .. ipython::
+    :verbatim:
+
+    In [1]: xr.Dataset({'foo': (('x', 'y'), [[1, 2]])})
+    Out[1]:
+    <xarray.Dataset>
+    Dimensions:  (x: 1, y: 2)
+    Coordinates:
+        *empty*
+    Unindexed dimensions:
+        x, y
+    Data variables:
+        foo      (x, y) int64 1 2
+
+  This has a number of implications:
 
   - :py:func:`~align` and :py:meth:`~Dataset.reindex` can now error, if
     dimensions labels are missing and dimensions have different sizes.

xarray/core/dataset.py

@@ -276,7 +276,7 @@ def __getitem__(self, key):
             raise KeyError(key)
 
     def __unicode__(self):
-        return formatting.vars_repr(self)
+        return formatting.data_vars_repr(self)
 
     @property
     def variables(self):

xarray/core/formatting.py

@@ -211,13 +211,6 @@ def _summarize_var_or_coord(name, var, col_width, show_values=True,
     return front_str + values_str
 
 
-def _summarize_dummy_var(name, col_width, marker=u'o', values=u'-'):
-    """Used if there is no coordinate for a dimension."""
-    first_col = pretty_print(u'  %s %s ' % (marker, name), col_width)
-    dims_str = u'(%s) ' % unicode_type(name)
-    return u'%s%s%s' % (first_col, dims_str, values)
-
-
 def _summarize_coord_multiindex(coord, col_width, marker):
     first_col = pretty_print(u'  %s %s ' % (marker, coord.name), col_width)
     return u'%s(%s) MultiIndex' % (first_col, unicode_type(coord.dims[0]))
@@ -248,8 +241,6 @@ def summarize_var(name, var, col_width):
 
 
 def summarize_coord(name, var, col_width):
-    if var is None:
-        return _summarize_dummy_var(name, col_width)
     is_index = name in var.dims
     show_values = is_index or _not_remote(var)
     marker = u'*' if is_index else u' '
@@ -305,8 +296,8 @@ def _mapping_repr(mapping, title, summarizer, col_width=None):
     return u'\n'.join(summary)
 
 
-vars_repr = functools.partial(_mapping_repr, title=u'Data variables',
-                              summarizer=summarize_var)
+data_vars_repr = functools.partial(_mapping_repr, title=u'Data variables',
+                                   summarizer=summarize_var)
 
 
 attrs_repr = functools.partial(_mapping_repr, title=u'Attributes',
@@ -316,12 +307,7 @@ def _mapping_repr(mapping, title, summarizer, col_width=None):
 def coords_repr(coords, col_width=None):
     if col_width is None:
         col_width = _calculate_col_width(_get_col_items(coords))
-    # augment coordinates to include markers for missing coordinates
-    augmented_coords = OrderedDict(coords)
-    for dim in coords.dims:
-        if dim not in augmented_coords:
-            augmented_coords[dim] = None
-    return _mapping_repr(augmented_coords, title=u'Coordinates',
+    return _mapping_repr(coords, title=u'Coordinates',
                          summarizer=summarize_coord, col_width=col_width)
 
 
@@ -337,6 +323,15 @@ def dim_summary(obj):
     return u', '.join(elements)
 
 
+def unindexed_dims_repr(dims, coords):
+    unindexed_dims = [d for d in dims if d not in coords]
+    if unindexed_dims:
+        dims_str = u', '.join(u'%s' % d for d in unindexed_dims)
+        return u'Unindexed dimensions:\n' + u' ' * 4 + dims_str
+    else:
+        return None
+
+      
 @contextlib.contextmanager
 def set_numpy_options(*args, **kwargs):
     original = np.get_printoptions()
@@ -386,6 +381,10 @@ def array_repr(arr):
         if arr.coords:
             summary.append(repr(arr.coords))
 
+        unindexed_dims_str = unindexed_dims_repr(arr.dims, arr.coords)
+        if unindexed_dims_str:
+            summary.append(unindexed_dims_str)
+
     if arr.attrs:
         summary.append(attrs_repr(arr.attrs))
 
@@ -401,7 +400,13 @@ def dataset_repr(ds):
     summary.append(u'%s(%s)' % (dims_start, dim_summary(ds)))
 
     summary.append(coords_repr(ds.coords, col_width=col_width))
-    summary.append(vars_repr(ds.data_vars, col_width=col_width))
+
+    unindexed_dims_str = unindexed_dims_repr(ds.dims, ds.coords)
+    if unindexed_dims_str:
+        summary.append(unindexed_dims_str)
+
+    summary.append(data_vars_repr(ds.data_vars, col_width=col_width))
+
     if ds.attrs:
         summary.append(attrs_repr(ds.attrs))
 

xarray/test/test_dataarray.py

@@ -46,7 +46,8 @@ def test_repr(self):
         Coordinates:
           * x        (x) int64 0 1 2
             other    int64 0
-          o time     (time) -
+        Unindexed dimensions:
+            time
         Attributes:
             foo: bar""")
         self.assertEqual(expected, repr(data_array))

xarray/test/test_dataset.py

@@ -91,7 +91,8 @@ def test_repr(self):
           * dim2     (dim2) float64 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
           * dim3     (dim3) %s 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j'
             numbers  (dim3) int64 0 1 2 0 0 1 1 2 2 3
-          o dim1     (dim1) -
+        Unindexed dimensions:
+            dim1
         Data variables:
             var1     (dim1, dim2) float64 -1.086 0.9973 0.283 -1.506 -0.5786 1.651 ...
             var2     (dim1, dim2) float64 1.162 -1.097 -2.123 1.04 -0.4034 -0.126 ...
@@ -203,25 +204,25 @@ def test_info(self):
         expected = dedent(u'''\
         xarray.Dataset {
         dimensions:
-        	dim1 = 8 ;
-        	dim2 = 9 ;
-        	dim3 = 10 ;
-        	time = 20 ;
+        \tdim1 = 8 ;
+        \tdim2 = 9 ;
+        \tdim3 = 10 ;
+        \ttime = 20 ;
 
         variables:
-        	datetime64[ns] time(time) ;
-        	float64 dim2(dim2) ;
-        	float64 var1(dim1, dim2) ;
-        		var1:foo = variable ;
-        	float64 var2(dim1, dim2) ;
-        		var2:foo = variable ;
-        	float64 var3(dim3, dim1) ;
-        		var3:foo = variable ;
-        	int64 numbers(dim3) ;
+        \tdatetime64[ns] time(time) ;
+        \tfloat64 dim2(dim2) ;
+        \tfloat64 var1(dim1, dim2) ;
+        \t\tvar1:foo = variable ;
+        \tfloat64 var2(dim1, dim2) ;
+        \t\tvar2:foo = variable ;
+        \tfloat64 var3(dim3, dim1) ;
+        \t\tvar3:foo = variable ;
+        \tint64 numbers(dim3) ;
 
         // global attributes:
-        	:unicode_attr = ba® ;
-        	:string_attr = bar ;
+        \t:unicode_attr = ba® ;
+        \t:string_attr = bar ;
         }''')
         actual = buf.getvalue()
         self.assertEqual(expected, actual)
@@ -685,6 +686,23 @@ def test_coords_merge_mismatched_shape(self):
         actual = orig_coords.merge(other_coords)
         self.assertDatasetIdentical(expected, actual)
 
+    def test_data_vars_properties(self):
+        ds = Dataset()
+        ds['foo'] = (('x',), [1.0])
+        ds['bar'] = 2.0
+
+        self.assertEqual(set(ds.data_vars), {'foo', 'bar'})
+        self.assertIn('foo', ds.data_vars)
+        self.assertNotIn('x', ds.data_vars)
+        self.assertDataArrayIdentical(ds['foo'], ds.data_vars['foo'])
+
+        expected = dedent("""\
+        Data variables:
+            foo      (x) float64 1.0
+            bar      float64 2.0""")
+        actual = repr(ds.data_vars)
+        self.assertEqual(expected, actual)
+
     def test_equals_and_identical(self):
         data = create_test_data(seed=42)
         self.assertTrue(data.equals(data))
@@ -3101,7 +3119,7 @@ def test_filter_by_attrs(self):
         ds = Dataset({'temperature_0': (['t'], [0], temp0),
                       'temperature_10': (['t'], [0], temp10),
                       'precipitation': (['t'], [0], precip)},
-                    coords={'time': (['t'], [0], dict(axis='T'))})
+                     coords={'time': (['t'], [0], dict(axis='T'))})
 
         # Test return empty Dataset.
         ds.filter_by_attrs(standard_name='invalid_standard_name')