String dtype: allow string dtype for non-raw apply with numba engine (#59854)

* String dtype: allow string dtype for non-raw apply with numba engine

* remove xfails

* clean-up

Author: jorisvandenbossche

pandas/core/_numba/extensions.py

@@ -53,7 +53,8 @@
 @contextmanager
 def set_numba_data(index: Index):
     numba_data = index._data
-    if numba_data.dtype == object:
+    if numba_data.dtype in (object, "string"):
+        numba_data = np.asarray(numba_data)
         if not lib.is_string_array(numba_data):
             raise ValueError(
                 "The numba engine only supports using string or numeric column names"

pandas/core/apply.py

@@ -1172,12 +1172,7 @@ def apply_with_numba(self) -> dict[int, Any]:
         from pandas.core._numba.extensions import set_numba_data
 
         index = self.obj.index
-        if index.dtype == "string":
-            index = index.astype(object)
-
         columns = self.obj.columns
-        if columns.dtype == "string":
-            columns = columns.astype(object)
 
         # Convert from numba dict to regular dict
         # Our isinstance checks in the df constructor don't pass for numbas typed dict

pandas/tests/apply/test_frame_apply.py

@@ -65,7 +65,6 @@ def test_apply(float_frame, engine, request):
         assert result.index is float_frame.index
 
 
-@pytest.mark.xfail(using_string_dtype(), reason="TODO(infer_string)", strict=False)
 @pytest.mark.parametrize("axis", [0, 1])
 @pytest.mark.parametrize("raw", [True, False])
 @pytest.mark.parametrize("nopython", [True, False])

pandas/tests/apply/test_numba.py

@@ -1,8 +1,6 @@
 import numpy as np
 import pytest
 
-from pandas._config import using_string_dtype
-
 import pandas.util._test_decorators as td
 
 import pandas as pd
@@ -20,7 +18,6 @@ def apply_axis(request):
     return request.param
 
 
-@pytest.mark.xfail(using_string_dtype(), reason="TODO(infer_string)")
 def test_numba_vs_python_noop(float_frame, apply_axis):
     func = lambda x: x
     result = float_frame.apply(func, engine="numba", axis=apply_axis)
@@ -43,7 +40,6 @@ def test_numba_vs_python_string_index():
     )
 
 
-@pytest.mark.xfail(using_string_dtype(), reason="TODO(infer_string)")
 def test_numba_vs_python_indexing():
     frame = DataFrame(
         {"a": [1, 2, 3], "b": [4, 5, 6], "c": [7.0, 8.0, 9.0]},