Compile regexes

Author: dcherian

cf_xarray/accessor.py

@@ -1363,8 +1363,6 @@ def guess_coord_axis(self, verbose: bool = False) -> Union[DataArray, Dataset]:
         -------
         DataArray or Dataset with appropriate attributes added
         """
-        import re
-
         obj = self._obj.copy(deep=True)
         for var in obj.coords.variables:
             if obj[var].ndim == 1 and _is_datetime_like(obj[var]):
@@ -1375,14 +1373,14 @@ def guess_coord_axis(self, verbose: bool = False) -> Union[DataArray, Dataset]:
                 obj[var].attrs = dict(ChainMap(obj[var].attrs, ATTRS["time"]))
                 continue  # prevent second detection
 
-            for axis, pattern in regex.items():
+            for name, pattern in regex.items():
                 # match variable names
-                if re.match(pattern, var.lower()):
+                if pattern.match(var.lower()):
                     if verbose:
                         print(
-                            f"I think {var!r} is of type {axis!r}. It matched {pattern!r}"
+                            f"I think {var!r} is of type {name!r}. It matched {pattern!r}"
                         )
-                    obj[var].attrs = dict(ChainMap(obj[var].attrs, ATTRS[axis]))
+                    obj[var].attrs = dict(ChainMap(obj[var].attrs, ATTRS[name]))
         return obj
 
     def drop(self, *args, **kwargs):

cf_xarray/criteria.py

@@ -5,6 +5,7 @@
 """
 
 
+import re
 from typing import MutableMapping, Tuple
 
 coordinate_criteria: MutableMapping[str, MutableMapping[str, Tuple]] = {
@@ -77,15 +78,15 @@
 
 #: regular expressions for guess_coord_axis
 regex = {
-    "time": "\\bt\\b|(time|min|hour|day|week|month|year)[0-9]*",
-    "vertical": (
+    "time": re.compile("\\bt\\b|(time|min|hour|day|week|month|year)[0-9]*"),
+    "vertical": re.compile(
         "(z|nav_lev|gdep|lv_|bottom_top|sigma|h(ei)?ght|altitude|depth|"
         "isobaric|pres|isotherm)[a-z_]*[0-9]*"
     ),
-    "Y": "y",
-    "latitude": "y?(nav_lat|lat|gphi)[a-z0-9]*",
-    "X": "x",
-    "longitude": "x?(nav_lon|lon|glam)[a-z0-9]*",
+    "Y": re.compile("y"),
+    "latitude": re.compile("y?(nav_lat|lat|gphi)[a-z0-9]*"),
+    "X": re.compile("x"),
+    "longitude": re.compile("x?(nav_lon|lon|glam)[a-z0-9]*"),
 }
 regex["Z"] = regex["vertical"]
 regex["T"] = regex["time"]