From 320823a49d48bd27c216264f9b128ed49fd1ac53 Mon Sep 17 00:00:00 2001
From: ben <ben@rain.local>
Date: Wed, 22 Apr 2026 22:37:31 -0700
Subject: [PATCH] GH-43574: [Python] do not add partition columns from file
 path when reading single file

Reverts a small portion of bd444106af494b3d4c6cce0af88f6ce2a6a327eb
---
 python/pyarrow/parquet/core.py               |  2 ++
 python/pyarrow/tests/parquet/test_dataset.py | 21 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/python/pyarrow/parquet/core.py b/python/pyarrow/parquet/core.py
index 19d8250d5101..5234976a921b 100644
--- a/python/pyarrow/parquet/core.py
+++ b/python/pyarrow/parquet/core.py
@@ -1446,6 +1446,8 @@ def __init__(self, path_or_paths, filesystem=None, schema=None, *, filters=None,
                     path_or_paths, filesystem, memory_map=memory_map
                 )
                 finfo = filesystem.get_file_info(path_or_paths)
+                if finfo.is_file:
+                    single_file = path_or_paths
                 if finfo.type == FileType.Directory:
                     self._base_dir = path_or_paths
             else:
diff --git a/python/pyarrow/tests/parquet/test_dataset.py b/python/pyarrow/tests/parquet/test_dataset.py
index d3e9cda73018..5f04a4889391 100644
--- a/python/pyarrow/tests/parquet/test_dataset.py
+++ b/python/pyarrow/tests/parquet/test_dataset.py
@@ -1250,6 +1250,27 @@ def test_parquet_dataset_new_filesystem(tempdir):
     assert result.equals(table)
 
 
+def test_parquet_dataset_partitions_not_loaded_for_single_file(tempdir):
+    # Ensure single-file reads do not include partitions from higher levels of the path
+    table = pa.table({'a': [1, 2, 3]})
+    path = tempdir / 'p=a' / 'data.parquet'
+    path.parent.mkdir()
+    pq.write_table(table, path)
+    # read using a path object
+    dataset = pq.ParquetDataset(path)
+    path_schema = dataset.schema
+    result = dataset.read()
+    assert result.equals(table)
+    # read using a file object; expect same result
+    with path.open("rb") as file:
+        dataset = pq.ParquetDataset(file)
+        file_schema = dataset.schema
+        result = dataset.read()
+    assert result.equals(table)
+    # schemas should match
+    assert path_schema.equals(file_schema)
+
+
 def test_parquet_dataset_partitions_piece_path_with_fsspec(tempdir):
     # ARROW-10462 ensure that on Windows we properly use posix-style paths
     # as used by fsspec