Update test_preserve_leading_zeros.py

Author: dxdc

pandas/tests/io/parser/test_preserve_leading_zeros.py

@@ -1,48 +1,71 @@
-import pytest
 from io import StringIO
-import pandas._testing as tm
+
+import pytest
 
 
-@pytest.mark.xfail(reason="Leading zeros preservation may not work consistently across all engines")
+@pytest.mark.xfail(
+    condition=getattr(all_parsers, "engine", "") == "pyarrow",
+    reason="pyarrow engine strips leading zeros even with dtype=str",
+)
 def test_leading_zeros_preserved_with_dtype_str(all_parsers):
     """
     Ensure that all parser engines preserve leading zeros when dtype=str is passed.
-    
-    This test verifies that when dtype=str is specified, leading zeros in 
+
+    This test verifies that when dtype=str is specified, leading zeros in
     numeric-looking strings are preserved across all available parser engines.
     """
     parser = all_parsers
-    engine_name = getattr(parser, 'engine', 'unknown')
-    
+    engine_name = getattr(parser, "engine", "unknown")
+
     data = """col1|col2|col3|col4
 AB|000388907|abc|0150
 CD|101044572|def|0150
 EF|000023607|ghi|0205
 GH|100102040|jkl|0205"""
-    
+
     result = parser.read_csv(
         StringIO(data),
         sep="|",
         dtype=str,
     )
-    
+
     # Verify leading zeros are preserved in col2
-    assert result.loc[0, "col2"] == "000388907", f"Engine {engine_name}: Leading zeros lost in col2, row 0. Got: {result.loc[0, 'col2']}"
-    assert result.loc[2, "col2"] == "000023607", f"Engine {engine_name}: Leading zeros lost in col2, row 2. Got: {result.loc[2, 'col2']}"
-    
+    assert result.loc[0, "col2"] == "000388907", (
+        f"Engine {engine_name}: Leading zeros lost in col2, row 0. Got: {result.loc[0, 'col2']}"
+    )
+    assert result.loc[2, "col2"] == "000023607", (
+        f"Engine {engine_name}: Leading zeros lost in col2, row 2. Got: {result.loc[2, 'col2']}"
+    )
+
     # Verify leading zeros are preserved in col4
-    assert result.loc[0, "col4"] == "0150", f"Engine {engine_name}: Leading zeros lost in col4, row 0. Got: {result.loc[0, 'col4']}"
-    assert result.loc[2, "col4"] == "0205", f"Engine {engine_name}: Leading zeros lost in col4, row 2. Got: {result.loc[2, 'col4']}"
-    
+    assert result.loc[0, "col4"] == "0150", (
+        f"Engine {engine_name}: Leading zeros lost in col4, row 0. Got: {result.loc[0, 'col4']}"
+    )
+    assert result.loc[2, "col4"] == "0205", (
+        f"Engine {engine_name}: Leading zeros lost in col4, row 2. Got: {result.loc[2, 'col4']}"
+    )
+
     # Verify all columns are string type
-    assert result.dtypes["col1"] == "object", f"Engine {engine_name}: col1 should be string type, got {result.dtypes['col1']}"
-    assert result.dtypes["col2"] == "object", f"Engine {engine_name}: col2 should be string type, got {result.dtypes['col2']}"
-    assert result.dtypes["col3"] == "object", f"Engine {engine_name}: col3 should be string type, got {result.dtypes['col3']}"
-    assert result.dtypes["col4"] == "object", f"Engine {engine_name}: col4 should be string type, got {result.dtypes['col4']}"
-    
+    assert result.dtypes["col1"] == "object", (
+        f"Engine {engine_name}: col1 should be string type, got {result.dtypes['col1']}"
+    )
+    assert result.dtypes["col2"] == "object", (
+        f"Engine {engine_name}: col2 should be string type, got {result.dtypes['col2']}"
+    )
+    assert result.dtypes["col3"] == "object", (
+        f"Engine {engine_name}: col3 should be string type, got {result.dtypes['col3']}"
+    )
+    assert result.dtypes["col4"] == "object", (
+        f"Engine {engine_name}: col4 should be string type, got {result.dtypes['col4']}"
+    )
+
     # Verify shape
-    assert result.shape == (4, 4), f"Engine {engine_name}: Expected shape (4, 4), got {result.shape}"
-    
+    assert result.shape == (4, 4), (
+        f"Engine {engine_name}: Expected shape (4, 4), got {result.shape}"
+    )
+
     # Verify column names
     expected_columns = ["col1", "col2", "col3", "col4"]
-    assert list(result.columns) == expected_columns, f"Engine {engine_name}: Expected columns {expected_columns}, got {list(result.columns)}"
+    assert list(result.columns) == expected_columns, (
+        f"Engine {engine_name}: Expected columns {expected_columns}, got {list(result.columns)}"
+    )