Clean up utils (#131)

Author: dcherian

cf_xarray/accessor.py

@@ -2,7 +2,7 @@
 import inspect
 import itertools
 import warnings
-from collections import ChainMap, defaultdict
+from collections import ChainMap
 from typing import (
     Any,
     Callable,
@@ -21,7 +21,7 @@
 from xarray import DataArray, Dataset
 
 from .helpers import bounds_to_vertices
-from .utils import parse_cell_methods_attr
+from .utils import _is_datetime_like, invert_mappings, parse_cell_methods_attr
 
 #: Classes wrapped by cf_xarray.
 _WRAPPED_CLASSES = (
@@ -140,37 +140,6 @@
 attrs["vertical"] = attrs["Z"]
 
 
-def _is_datetime_like(da: DataArray) -> bool:
-    import numpy as np
-
-    if np.issubdtype(da.dtype, np.datetime64) or np.issubdtype(
-        da.dtype, np.timedelta64
-    ):
-        return True
-
-    try:
-        import cftime
-
-        if isinstance(da.data[0], cftime.datetime):
-            return True
-    except ImportError:
-        pass
-
-    return False
-
-
-def invert_mappings(*mappings):
-    """Takes a set of mappings and iterates through, inverting to make a
-    new mapping of value: set(keys). Keys are deduplicated to avoid clashes between
-    standard_name and coordinate names."""
-    merged = defaultdict(set)
-    for mapping in mappings:
-        for k, v in mapping.items():
-            for name in v:
-                merged[name] |= set([k])
-    return merged
-
-
 # Type for Mapper functions
 Mapper = Callable[[Union[DataArray, Dataset], str], List[str]]
 

cf_xarray/utils.py

@@ -1,52 +1,26 @@
-from typing import Any, Dict, Hashable, Mapping, Optional, TypeVar, cast
+from collections import defaultdict
+from typing import Dict
 
-K = TypeVar("K")
-V = TypeVar("V")
-T = TypeVar("T")
+from xarray import DataArray
 
 
-def either_dict_or_kwargs(
-    pos_kwargs: Optional[Mapping[Hashable, T]],
-    kw_kwargs: Mapping[str, T],
-    func_name: str,
-) -> Mapping[Hashable, T]:
-    if pos_kwargs is not None:
-        if not is_dict_like(pos_kwargs):
-            raise ValueError(
-                "the first argument to .%s must be a dictionary" % func_name
-            )
-        if kw_kwargs:
-            raise ValueError(
-                "cannot specify both keyword and positional "
-                "arguments to .%s" % func_name
-            )
-        return pos_kwargs
-    else:
-        # Need an explicit cast to appease mypy due to invariance; see
-        # https://github.com/python/mypy/issues/6228
-        return cast(Mapping[Hashable, T], kw_kwargs)
+def _is_datetime_like(da: DataArray) -> bool:
+    import numpy as np
 
+    if np.issubdtype(da.dtype, np.datetime64) or np.issubdtype(
+        da.dtype, np.timedelta64
+    ):
+        return True
 
-def is_dict_like(value: Any) -> bool:
-    return hasattr(value, "keys") and hasattr(value, "__getitem__")
+    try:
+        import cftime
 
+        if isinstance(da.data[0], cftime.datetime):
+            return True
+    except ImportError:
+        pass
 
-# 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)
+    return False
 
 
 def parse_cell_methods_attr(attr: str) -> Dict[str, str]:
@@ -67,3 +41,15 @@ def parse_cell_methods_attr(attr: str) -> Dict[str, str]:
         raise ValueError(f"attrs['cell_measures'] = {attr!r} is malformed.")
 
     return dict(zip(strings[slice(0, None, 2)], strings[slice(1, None, 2)]))
+
+
+def invert_mappings(*mappings):
+    """Takes a set of mappings and iterates through, inverting to make a
+    new mapping of value: set(keys). Keys are deduplicated to avoid clashes between
+    standard_name and coordinate names."""
+    merged = defaultdict(set)
+    for mapping in mappings:
+        for k, v in mapping.items():
+            for name in v:
+                merged[name] |= set([k])
+    return merged