fix: fixed-offset datetime weren't being parsed (#1303)

* fix: fix parsing of fixed-offset timezones

* vresions

Author: MarcoGorelli

narwhals/_pandas_like/utils.py

@@ -30,6 +30,51 @@
     Implementation.CUDF,
     Implementation.MODIN,
 }
+PD_DATETIME_RGX = r"""^
+    datetime64\[
+        (?P<time_unit>s|ms|us|ns)                 # Match time unit: s, ms, us, or ns
+        (?:,                                      # Begin non-capturing group for optional timezone
+            \s*                                   # Optional whitespace after comma
+            (?P<time_zone>                        # Start named group for timezone
+                [a-zA-Z\/]+                       # Match timezone name, e.g., UTC, America/New_York
+                (?:[+-]\d{2}:\d{2})?              # Optional offset in format +HH:MM or -HH:MM
+                |                                 # OR
+                pytz\.FixedOffset\(\d+\)          # Match pytz.FixedOffset with integer offset in parentheses
+            )                                     # End time_zone group
+        )?                                        # End optional timezone group
+    \]                                            # Closing bracket for datetime64
+$"""
+PATTERN_PD_DATETIME = re.compile(PD_DATETIME_RGX, re.VERBOSE)
+PA_DATETIME_RGX = r"""^
+    timestamp\[
+        (?P<time_unit>s|ms|us|ns)                 # Match time unit: s, ms, us, or ns
+        (?:,                                      # Begin non-capturing group for optional timezone
+            \s?tz=                                # Match "tz=" prefix
+            (?P<time_zone>                        # Start named group for timezone
+                [a-zA-Z\/]*                       # Match timezone name (e.g., UTC, America/New_York)
+                (?:                               # Begin optional non-capturing group for offset
+                    [+-]\d{2}:\d{2}               # Match offset in format +HH:MM or -HH:MM
+                )?                                # End optional offset group
+            )                                     # End time_zone group
+        )?                                        # End optional timezone group
+    \]                                            # Closing bracket for timestamp
+    \[pyarrow\]                                   # Literal string "[pyarrow]"
+$"""
+PATTERN_PA_DATETIME = re.compile(PA_DATETIME_RGX, re.VERBOSE)
+PD_DURATION_RGX = r"""^
+    timedelta64\[
+        (?P<time_unit>s|ms|us|ns)                 # Match time unit: s, ms, us, or ns
+    \]                                            # Closing bracket for timedelta64
+$"""
+
+PATTERN_PD_DURATION = re.compile(PD_DURATION_RGX, re.VERBOSE)
+PA_DURATION_RGX = r"""^
+    duration\[
+        (?P<time_unit>s|ms|us|ns)                 # Match time unit: s, ms, us, or ns
+    \]                                            # Closing bracket for duration
+    \[pyarrow\]                                   # Literal string "[pyarrow]"
+$"""
+PATTERN_PA_DURATION = re.compile(PA_DURATION_RGX, re.VERBOSE)
 
 
 def validate_column_comparand(index: Any, other: Any) -> Any:
@@ -223,14 +268,6 @@ def native_to_narwhals_dtype(
 ) -> DType:
     dtype = str(native_column.dtype)
 
-    pd_datetime_rgx = (
-        r"^datetime64\[(?P<time_unit>s|ms|us|ns)(?:, (?P<time_zone>[a-zA-Z\/]+))?\]$"
-    )
-    pa_datetime_rgx = r"^timestamp\[(?P<time_unit>s|ms|us|ns)(?:, tz=(?P<time_zone>[a-zA-Z\/]+))?\]\[pyarrow\]$"
-
-    pd_duration_rgx = r"^timedelta64\[(?P<time_unit>s|ms|us|ns)\]$"
-    pa_duration_rgx = r"^duration\[(?P<time_unit>s|ms|us|ns)\]\[pyarrow\]$"
-
     if dtype in {"int64", "Int64", "Int64[pyarrow]", "int64[pyarrow]"}:
         return dtypes.Int64()
     if dtype in {"int32", "Int32", "Int32[pyarrow]", "int32[pyarrow]"}:
@@ -269,14 +306,14 @@ def native_to_narwhals_dtype(
         return dtypes.Boolean()
     if dtype == "category" or dtype.startswith("dictionary<"):
         return dtypes.Categorical()
-    if (match_ := re.match(pd_datetime_rgx, dtype)) or (
-        match_ := re.match(pa_datetime_rgx, dtype)
+    if (match_ := PATTERN_PD_DATETIME.match(dtype)) or (
+        match_ := PATTERN_PA_DATETIME.match(dtype)
     ):
         dt_time_unit: Literal["us", "ns", "ms", "s"] = match_.group("time_unit")  # type: ignore[assignment]
         dt_time_zone: str | None = match_.group("time_zone")
         return dtypes.Datetime(dt_time_unit, dt_time_zone)
-    if (match_ := re.match(pd_duration_rgx, dtype)) or (
-        match_ := re.match(pa_duration_rgx, dtype)
+    if (match_ := PATTERN_PD_DURATION.match(dtype)) or (
+        match_ := PATTERN_PA_DURATION.match(dtype)
     ):
         du_time_unit: Literal["us", "ns", "ms", "s"] = match_.group("time_unit")  # type: ignore[assignment]
         return dtypes.Duration(du_time_unit)

tests/dtypes_test.py

@@ -176,3 +176,24 @@ def test_pandas_inplace_modification_1267(request: pytest.FixtureRequest) -> Non
     assert snw.dtype == nw.Int64
     s[0] = 999.5
     assert snw.dtype == nw.Float64
+
+
+def test_pandas_fixed_offset_1302() -> None:
+    result = nw.from_native(
+        pd.Series(pd.to_datetime(["2020-01-01T00:00:00.000000000+01:00"])),
+        series_only=True,
+    ).dtype
+    if PANDAS_VERSION >= (2,):
+        assert result == nw.Datetime("ns", "UTC+01:00")
+    else:  # pragma: no cover
+        assert result == nw.Datetime("ns", "pytz.FixedOffset(60)")
+    if PANDAS_VERSION >= (2,):
+        result = nw.from_native(
+            pd.Series(
+                pd.to_datetime(["2020-01-01T00:00:00.000000000+01:00"])
+            ).convert_dtypes(dtype_backend="pyarrow"),
+            series_only=True,
+        ).dtype
+        assert result == nw.Datetime("ns", "+01:00")
+    else:  # pragma: no cover
+        pass