Copilot commented on code in PR #50327:
URL: https://github.com/apache/arrow/pull/50327#discussion_r3509608761
##########
python/pyarrow/array.pxi:
##########
@@ -3974,6 +4155,45 @@ cdef class StringArray(Array):
Concrete class for Arrow arrays of string (or utf8) data type.
"""
+ def to_pylist(self, *, maps_as_pydicts=None):
+ """
+ Convert to a list of native Python objects.
+
+ Parameters
+ ----------
+ maps_as_pydicts : str, optional, default `None`
+ Valid values are `None`, 'lossy', or 'strict'.
+ This parameter is ignored for non-nested Arrays.
+
+ Returns
+ -------
+ lst : list
+ """
+ cdef:
+ CStringArray* arr = <CStringArray*> self.ap
+ int64_t i, n
+ int32_t length
+ const uint8_t* data
+ self._assert_cpu()
+ n = arr.length()
+ result = []
+ # Decode values straight from the data buffer instead of creating
+ # a C++ Scalar and a Python Scalar wrapper per value (see GH-28694).
+ if arr.null_count() == 0:
+ for i in range(n):
+ data = arr.GetValue(i, &length)
+ result.append(
+ cp.PyUnicode_DecodeUTF8(<const char*> data, length, NULL))
+ else:
+ for i in range(n):
+ if arr.IsNull(i):
+ result.append(None)
+ else:
+ data = arr.GetValue(i, &length)
+ result.append(
+ cp.PyUnicode_DecodeUTF8(<const char*> data, length,
NULL))
+ return result
Review Comment:
Using `arr.null_count() == 0` can force an extra full validity-bitmap scan
when `null_count` is unknown (e.g., slices of arrays with any nulls), because
`null_count()` computes and caches the count. Since the else-branch already
calls `IsNull(i)` per element, this can add an avoidable extra pass; consider
branching on `arr.null_bitmap_data() == NULL` (definitely no nulls) and
otherwise doing per-element `IsNull(i)` without calling `null_count()` (apply
similarly to LargeStringArray / list bulk paths).
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