docs (#48)

* docs

* update isort call.

* update pre-commit

* fix isort

.github/workflows/linting.yaml

@@ -59,4 +59,4 @@ jobs:
           python -m pip install isort
       - name: isort check
         run: |
-          isort --recursive --check-only .
+          isort --check-only .

.pre-commit-config.yaml

@@ -2,7 +2,7 @@
 repos:
   # isort should run before black as black sometimes tweaks the isort output
   - repo: https://github.com/timothycrosley/isort
-    rev: 4.3.21-2
+    rev: 5.0.4
     hooks:
       - id: isort
         files: .+\.py$
@@ -16,7 +16,7 @@ repos:
     hooks:
       - id: flake8
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v0.781  # Must match ci/requirements/*.yml
+    rev: v0.782  # Must match ci/requirements/*.yml
     hooks:
       - id: mypy
   # run this occasionally, ref discussion https://github.com/pydata/xarray/pull/3194

cf_xarray/accessor.py

@@ -149,11 +149,11 @@ def _get_axis_coord(
 
     Parameters
     ----------
-    var : DataArray, Dataset
+    var: DataArray, Dataset
         DataArray belonging to the coordinate to be checked
-    key : str, ["X", "Y", "Z", "T", "longitude", "latitude", "vertical", "time"]
+    key: str, ["X", "Y", "Z", "T", "longitude", "latitude", "vertical", "time"]
         key to check for.
-    error : bool
+    error: bool
         raise errors when key is not found or interpretable. Use False and provide default
         to replicate dict.get(k, None).
     default: Any
@@ -217,7 +217,24 @@ def _get_measure(
     da: xr.DataArray, key: str, error: bool = True, default: str = None
 ) -> Optional[str]:
     """
-    Interprets 'cell_measures'.
+    Translate from cell measures ("area" or "volume") to appropriate variable name.
+    This function interprets the ``cell_measures`` attribute on DataArrays.
+
+    Parameters
+    ----------
+    da: DataArray
+        DataArray belonging to the coordinate to be checked
+    key: str, ["area", "volume"]
+        key to check for.
+    error: bool
+        raise errors when key is not found or interpretable. Use False and provide default
+        to replicate dict.get(k, None).
+    default: Any
+        default value to return when error is False.
+
+    Returns
+    -------
+    List[str], Variable name(s) in parent xarray object that matches axis or coordinate `key`
     """
     if not isinstance(da, DataArray):
         raise NotImplementedError("Measures not implemented for Datasets yet.")
@@ -254,6 +271,9 @@ def _get_measure(
 
 
 #: Default mappers for common keys.
+# TODO: Make the values of this a tuple,
+#       so that multiple mappers can be used for a single key
+#       We need this for groupby("T.month") and groupby("latitude") for example.
 _DEFAULT_KEY_MAPPERS: Mapping[str, Mapper] = {
     "dim": _get_axis_coord,
     "dims_or_levels": _get_axis_coord,  # reset_index
@@ -280,7 +300,19 @@ def _filter_by_standard_names(ds: xr.Dataset, name: Union[str, List[str]]) -> Li
 
 
 def _get_list_standard_names(obj: xr.Dataset) -> List[str]:
-    """ Returns a sorted list of standard names in Dataset. """
+    """
+    Returns a sorted list of standard names in Dataset.
+
+    Parameters
+    ----------
+
+    obj: DataArray, Dataset
+        Xarray objec to process
+
+    Returns
+    -------
+    list of standard names in dataset
+    """
     names = []
     for k, v in obj.variables.items():
         if "standard_name" in v.attrs:
@@ -332,15 +364,18 @@ def wrapper(*args, **kwargs):
 
 
 class _CFWrappedClass:
+    """
+    This class is used to wrap any class in _WRAPPED_CLASSES.
+    """
+
     def __init__(self, towrap, accessor: "CFAccessor"):
         """
-        This class is used to wrap any class in _WRAPPED_CLASSES.
-
         Parameters
         ----------
         towrap : Resample, GroupBy, Coarsen, Rolling, Weighted
             Instance of xarray class that is being wrapped.
         accessor : CFAccessor
+            Parent accessor object
         """
         self.wrapped = towrap
         self.accessor = accessor
@@ -369,7 +404,10 @@ def __init__(self, obj, accessor):
 
     def _plot_decorator(self, func):
         """
-        This decorator is used to set kwargs on plotting functions.
+        This decorator is used to set default kwargs on plotting functions.
+
+        For now, this is setting ``xincrease`` and ``yincrease``. It could set
+        other arguments in the future.
         """
         valid_keys = self.accessor.get_valid_keys()
 
@@ -402,6 +440,9 @@ def _plot_wrapper(*args, **kwargs):
         return _plot_wrapper
 
     def __call__(self, *args, **kwargs):
+        """
+        Allows .plot()
+        """
         plot = _getattr(
             obj=self._obj,
             attr="plot",
@@ -411,6 +452,9 @@ def __call__(self, *args, **kwargs):
         return self._plot_decorator(plot)(*args, **kwargs)
 
     def __getattr__(self, attr):
+        """
+        Wraps .plot.contour() for example.
+        """
         return _getattr(
             obj=self._obj.plot,
             attr=attr,
@@ -423,10 +467,21 @@ def __getattr__(self, attr):
 
 
 class CFAccessor:
+    """
+    Common Dataset and DataArray accessor functionality.
+    """
+
     def __init__(self, da):
         self._obj = da
 
-    def _process_signature(self, func, args, kwargs, key_mappers):
+    def _process_signature(self, func: Callable, args, kwargs, key_mappers):
+        """
+        Processes a function's signature, args, kwargs:
+        1. Binds *args so that everthing is a Mapping from kwarg name to values
+        2. Calls _rewrite_values to rewrite any special CF names to normal xarray names.
+           This uses key_mappers
+        3. Unpacks arguments if necessary before returning them.
+        """
         sig = inspect.signature(func, follow_wrapped=False)
 
         # Catch things like .isel(T=5).
@@ -456,7 +511,24 @@ def _process_signature(self, func, args, kwargs, key_mappers):
         return arguments
 
     def _rewrite_values(self, kwargs, key_mappers: dict, var_kws):
-        """ rewrites 'dim' for example using 'mapper' """
+        """
+        Rewrites the values in a Mapping from kwarg to value.
+
+        Parameters
+        ----------
+        kwargs: Mapping
+            Mapping from kwarg name to value
+        key_mappers: Mapping
+            Mapping from kwarg name to a Mapper function that will convert a
+            given CF "special" name to an xarray name.
+        var_kws: List[str]
+            List of variable kwargs that need special treatment.
+            e.g. **indexers_kwargs in isel
+
+        Returns
+        -------
+        dict of kwargs with fully rewritten values.
+        """
         updates: dict = {}
 
         # allow multiple return values here.
@@ -558,11 +630,17 @@ def _describe(self):
         return text
 
     def describe(self):
+        """
+        Print a string repr to screen.
+        """
         print(self._describe())
 
     def get_valid_keys(self) -> Set[str]:
         """
-        Returns valid keys for .cf[]
+        Utility function that returns valid keys for .cf[].
+
+        This is useful for checking whether a key is valid for indexing, i.e.
+        that the attributes necessary to allow indexing by that key exist.
 
         Returns
         -------

cf_xarray/tests/test_accessor.py

@@ -1,7 +1,7 @@
 import matplotlib as mpl
-import matplotlib.pyplot as plt
 import pytest
 import xarray as xr
+from matplotlib import pyplot as plt
 from xarray.testing import assert_identical
 
 import cf_xarray  # noqa

cf_xarray/utils.py

@@ -29,3 +29,21 @@ def either_dict_or_kwargs(
 
 def is_dict_like(value: Any) -> bool:
     return hasattr(value, "keys") and hasattr(value, "__getitem__")
+
+
+# copied from xarray
+class UncachedAccessor:
+    """ Acts like a property, but on both classes and class instances
+    This class is necessary because some tools (e.g. pydoc and sphinx)
+    inspect classes for which property returns itself and not the
+    accessor.
+    """
+
+    def __init__(self, accessor):
+        self._accessor = accessor
+
+    def __get__(self, obj, cls):
+        if obj is None:
+            return self._accessor
+
+        return self._accessor(obj)

doc/api.rst

@@ -10,7 +10,7 @@ DataArray
    :toctree: generated/
    :template: autosummary/accessor_attribute.rst
 
-
+    DataArray.cf.plot
 
 .. autosummary::
    :toctree: generated/
@@ -26,8 +26,6 @@ Dataset
    :toctree: generated/
    :template: autosummary/accessor_attribute.rst
 
-
-
 .. autosummary::
    :toctree: generated/
    :template: autosummary/accessor_method.rst

doc/contributing.rst

@@ -1,15 +1,59 @@
 .. currentmodule:: cf_xarray
 
+.. ipython:: python
+    :suppress:
+
+    import cf_xarray.accessor
+
 Contributing
 --------------
 
-This section will be expanded later.
-
-.. autodata:: cf_xarray.accessor.coordinate_criteria
-.. autodata:: cf_xarray.accessor._WRAPPED_CLASSES
+This section will be expanded later. For now it lists docstrings for a number of internal variables, classes and functions.
 
-The following names are "special"
+Variables
+~~~~~~~~~
 
 .. autodata:: cf_xarray.accessor._AXIS_NAMES
-.. autodata:: cf_xarray.accessor._COORD_NAMES
 .. autodata:: cf_xarray.accessor._CELL_MEASURES
+.. autodata:: cf_xarray.accessor._COORD_NAMES
+.. autodata:: cf_xarray.accessor._WRAPPED_CLASSES
+
+
+Attribute parsing
++++++++++++++++++
+
+This dictionary contains criteria for identifying axis and coords using CF attributes. It was copied from MetPy
+
+.. autosummary::
+   :toctree: generated/
+
+   ~accessor.coordinate_criteria
+
+Classes
+~~~~~~~
+
+.. autosummary::
+   :toctree: generated/
+   :template: autosummary/accessor_class.rst
+
+
+    ~accessor.CFAccessor
+    ~accessor._CFWrappedClass
+    ~accessor._CFWrappedPlotMethods
+
+Functions
+~~~~~~~~~
+
+
+Primarily for developer reference. Some of these could become public API if necessary.
+
+.. autosummary::
+   :toctree: generated/
+
+    ~accessor._getattr
+    ~accessor._get_axis_coord
+    ~accessor._get_axis_coord_single
+    ~accessor._get_list_standard_names
+    ~accessor._get_measure
+    ~accessor._get_measure_variable
+    accessor._CFWrappedPlotMethods._plot_decorator