chore: Move _is_naive_format helper function into utils.py (#2568)

chore: Move _is_naive_format helper function into utils.py

Author: FBruzzesi

narwhals/_ibis/expr_str.py

@@ -6,6 +6,7 @@
 
 from ibis.expr.datatypes import Timestamp
 
+from narwhals.utils import _is_naive_format
 from narwhals.utils import not_implemented
 
 if TYPE_CHECKING:
@@ -103,7 +104,3 @@ def to_datetime(self, format: str | None) -> IbisExpr:
         return self._compliant_expr._with_callable(fn(format))
 
     replace = not_implemented()
-
-
-def _is_naive_format(format_: str) -> bool:
-    return not any(x in format_ for x in ("%s", "%z", "Z"))

narwhals/_spark_like/expr_str.py

@@ -3,6 +3,8 @@
 from functools import partial
 from typing import TYPE_CHECKING
 
+from narwhals.utils import _is_naive_format
+
 if TYPE_CHECKING:
     from sqlframe.base.column import Column
 
@@ -100,7 +102,7 @@ def to_datetime(self, format: str | None) -> SparkLikeExpr:
         F = self._compliant_expr._F  # noqa: N806
         if not format:
             function = F.to_timestamp
-        elif is_naive_format(format):
+        elif _is_naive_format(format):
             function = partial(
                 F.to_timestamp_ntz, format=F.lit(strptime_to_pyspark_format(format))
             )
@@ -112,10 +114,6 @@ def to_datetime(self, format: str | None) -> SparkLikeExpr:
         )
 
 
-def is_naive_format(format: str) -> bool:
-    return not any(x in format for x in ("%s", "%z", "Z"))
-
-
 def strptime_to_pyspark_format(format: str) -> str:
     """Converts a Python strptime datetime format string to a PySpark datetime format string."""
     # Mapping from Python strptime format to PySpark format

narwhals/utils.py

@@ -1745,6 +1745,24 @@ def unstable(fn: _Fn, /) -> _Fn:
     return fn
 
 
+def _is_naive_format(format: str) -> bool:
+    """Determines if a datetime format string is 'naive', i.e., does not include timezone information.
+
+    A format is considered naive if it does not contain any of the following
+
+    - '%s': Unix timestamp
+    - '%z': UTC offset
+    - 'Z' : UTC timezone designator
+
+    Arguments:
+        format: The datetime format string to check.
+
+    Returns:
+        bool: True if the format is naive (does not include timezone info), False otherwise.
+    """
+    return not any(x in format for x in ("%s", "%z", "Z"))
+
+
 if TYPE_CHECKING:
     import sys