also cache the units themselves

src/finam/data/tools.py

@@ -25,7 +25,8 @@ from .grid_tools import Grid, GridBase
 pint_xarray.unit_registry.default_format = "cf"
 UNITS = pint_xarray.unit_registry
 
-_UNITS_CACHE = {}
+_UNIT_CACHE = {}
+_UNIT_PAIRS_CACHE = {}
 
 
 def _gen_dims(ndim, info):
@@ -98,7 +99,7 @@ def to_xarray(data, name, info, time_entries=1, force_copy=False):
 
         return to_units(data, info.units)
 
-    units = UNITS.Unit(info.units)
+    units = _get_pint_units(info.units)
     if isinstance(data, pint.Quantity):
         if not compatible_units(data.units, units):
             raise FinamDataError(
@@ -329,7 +330,7 @@ def to_units(xdata, units):
         Converted data.
     """
     check_quantified(xdata, "to_units")
-    units = UNITS.Unit(units)
+    units = _get_pint_units(units)
     if units == xdata.pint.units:
         return xdata
     return xdata.pint.to(units)
@@ -435,11 +436,10 @@ def check(
             f"check: given data has wrong meta data.\nData: {xdata.attrs}\nMeta: {meta}"
         )
     # check units
-    units = UNITS.Unit(info.units)
-    if not compatible_units(units, xdata):
+    if not compatible_units(info.units, xdata):
         raise FinamDataError(
             f"check: given data has incompatible units. "
-            f"Got {get_units(xdata)}, expected {units}."
+            f"Got {get_units(xdata)}, expected {UNITS.Unit(info.units)}."
         )
 
 
@@ -518,7 +518,12 @@ def _get_pint_units(var):
     if isinstance(var, xr.DataArray):
         return var.pint.units or UNITS.dimensionless
 
-    return UNITS.Unit(var)
+    units = _UNIT_CACHE.get(var)
+    if units is None:
+        units = UNITS.Unit(var)
+        _UNIT_CACHE[var] = units
+
+    return units
 
 
 def compatible_units(unit1, unit2):
@@ -538,7 +543,7 @@ def compatible_units(unit1, unit2):
         Unit compatibility.
     """
     unit1, unit2 = _get_pint_units(unit1), _get_pint_units(unit2)
-    comp_equiv = _UNITS_CACHE.get((unit1, unit2))
+    comp_equiv = _UNIT_PAIRS_CACHE.get((unit1, unit2))
     if comp_equiv is None:
         comp_equiv = _cache_units(unit1, unit2)
 
@@ -562,7 +567,7 @@ def equivalent_units(unit1, unit2):
         Unit equivalence.
     """
     unit1, unit2 = _get_pint_units(unit1), _get_pint_units(unit2)
-    comp_equiv = _UNITS_CACHE.get((unit1, unit2))
+    comp_equiv = _UNIT_PAIRS_CACHE.get((unit1, unit2))
     if comp_equiv is None:
         comp_equiv = _cache_units(unit1, unit2)
 
@@ -578,13 +583,14 @@ def _cache_units(unit1, unit2):
     except pint.errors.DimensionalityError:
         pass
 
-    _UNITS_CACHE[(unit1, unit2)] = compat, equiv
+    _UNIT_PAIRS_CACHE[(unit1, unit2)] = compat, equiv
     return compat, equiv
 
 
 def clear_units_cache():
     """Clears the units cache"""
-    _UNITS_CACHE.clear()
+    _UNIT_CACHE.clear()
+    _UNIT_PAIRS_CACHE.clear()
 
 
 def assert_type(cls, slot, obj, types):