REG/REF: close file handles engine-independently in read_csv (#45389)

Author: twoertwein

doc/source/whatsnew/v1.4.0.rst

@@ -933,6 +933,7 @@ I/O
 - Bug in :func:`read_csv` when passing a ``tempfile.SpooledTemporaryFile`` opened in binary mode (:issue:`44748`)
 - Bug in :func:`read_json` raising ``ValueError`` when attempting to parse json strings containing "://" (:issue:`36271`)
 - Bug in :func:`read_csv` when ``engine="c"`` and ``encoding_errors=None`` which caused a segfault (:issue:`45180`)
+- Bug in :func:`read_csv` an invalid value of ``usecols`` leading to an un-closed file handle (:issue:`45384`)
 
 Period
 ^^^^^^

pandas/_typing.py

@@ -292,3 +292,6 @@ def closed(self) -> bool:
 
 # Windowing rank methods
 WindowingRankType = Literal["average", "min", "max"]
+
+# read_csv engines
+CSVEngine = Literal["c", "python", "pyarrow", "python-fwf"]

pandas/io/parsers/arrow_parser_wrapper.py

@@ -1,16 +1,12 @@
 from __future__ import annotations
 
-from pandas._typing import (
-    FilePath,
-    ReadBuffer,
-)
+from pandas._typing import ReadBuffer
 from pandas.compat._optional import import_optional_dependency
 
 from pandas.core.dtypes.inference import is_integer
 
 from pandas.core.frame import DataFrame
 
-from pandas.io.common import get_handle
 from pandas.io.parsers.base_parser import ParserBase
 
 
@@ -19,12 +15,11 @@ class ArrowParserWrapper(ParserBase):
     Wrapper for the pyarrow engine for read_csv()
     """
 
-    def __init__(self, src: FilePath | ReadBuffer[bytes], **kwds):
+    def __init__(self, src: ReadBuffer[bytes], **kwds):
+        super().__init__(kwds)
         self.kwds = kwds
         self.src = src
 
-        ParserBase.__init__(self, kwds)
-
         self._parse_kwds()
 
     def _parse_kwds(self):
@@ -151,15 +146,12 @@ def read(self) -> DataFrame:
         pyarrow_csv = import_optional_dependency("pyarrow.csv")
         self._get_pyarrow_options()
 
-        with get_handle(
-            self.src, "rb", encoding=self.encoding, is_text=False
-        ) as handles:
-            table = pyarrow_csv.read_csv(
-                handles.handle,
-                read_options=pyarrow_csv.ReadOptions(**self.read_options),
-                parse_options=pyarrow_csv.ParseOptions(**self.parse_options),
-                convert_options=pyarrow_csv.ConvertOptions(**self.convert_options),
-            )
+        table = pyarrow_csv.read_csv(
+            self.src,
+            read_options=pyarrow_csv.ReadOptions(**self.read_options),
+            parse_options=pyarrow_csv.ParseOptions(**self.parse_options),
+            convert_options=pyarrow_csv.ConvertOptions(**self.convert_options),
+        )
 
-            frame = table.to_pandas()
-            return self._finalize_output(frame)
+        frame = table.to_pandas()
+        return self._finalize_output(frame)

pandas/io/parsers/base_parser.py

@@ -7,7 +7,6 @@
 from enum import Enum
 import itertools
 from typing import (
-    Any,
     Callable,
     DefaultDict,
     Hashable,
@@ -32,8 +31,6 @@
 from pandas._typing import (
     ArrayLike,
     DtypeArg,
-    FilePath,
-    ReadCsvBuffer,
 )
 from pandas.errors import (
     ParserError,
@@ -71,10 +68,6 @@
 from pandas.core.series import Series
 from pandas.core.tools import datetimes as tools
 
-from pandas.io.common import (
-    IOHandles,
-    get_handle,
-)
 from pandas.io.date_converters import generic_parser
 
 
@@ -176,30 +169,10 @@ def __init__(self, kwds):
 
         self.usecols, self.usecols_dtype = self._validate_usecols_arg(kwds["usecols"])
 
-        self.handles: IOHandles[str] | None = None
-
         # Fallback to error to pass a sketchy test(test_override_set_noconvert_columns)
         # Normally, this arg would get pre-processed earlier on
         self.on_bad_lines = kwds.get("on_bad_lines", self.BadLineHandleMethod.ERROR)
 
-    def _open_handles(
-        self,
-        src: FilePath | ReadCsvBuffer[bytes] | ReadCsvBuffer[str],
-        kwds: dict[str, Any],
-    ) -> None:
-        """
-        Let the readers open IOHandles after they are done with their potential raises.
-        """
-        self.handles = get_handle(
-            src,
-            "r",
-            encoding=kwds.get("encoding", None),
-            compression=kwds.get("compression", None),
-            memory_map=kwds.get("memory_map", False),
-            storage_options=kwds.get("storage_options", None),
-            errors=kwds.get("encoding_errors", "strict"),
-        )
-
     def _validate_parse_dates_presence(self, columns: Sequence[Hashable]) -> Iterable:
         """
         Check if parse_dates are in columns.
@@ -262,8 +235,7 @@ def _validate_parse_dates_presence(self, columns: Sequence[Hashable]) -> Iterabl
         ]
 
     def close(self):
-        if self.handles is not None:
-            self.handles.close()
+        pass
 
     @final
     @property

pandas/io/parsers/c_parser_wrapper.py

@@ -14,7 +14,6 @@
     ArrayLike,
     DtypeArg,
     DtypeObj,
-    FilePath,
     ReadCsvBuffer,
 )
 from pandas.errors import DtypeWarning
@@ -43,12 +42,10 @@ class CParserWrapper(ParserBase):
     low_memory: bool
     _reader: parsers.TextReader
 
-    def __init__(
-        self, src: FilePath | ReadCsvBuffer[bytes] | ReadCsvBuffer[str], **kwds
-    ):
+    def __init__(self, src: ReadCsvBuffer[str], **kwds):
+        super().__init__(kwds)
         self.kwds = kwds
         kwds = kwds.copy()
-        ParserBase.__init__(self, kwds)
 
         self.low_memory = kwds.pop("low_memory", False)
 
@@ -61,10 +58,6 @@ def __init__(
         # GH20529, validate usecol arg before TextReader
         kwds["usecols"] = self.usecols
 
-        # open handles
-        self._open_handles(src, kwds)
-        assert self.handles is not None
-
         # Have to pass int, would break tests using TextReader directly otherwise :(
         kwds["on_bad_lines"] = self.on_bad_lines.value
 
@@ -79,11 +72,7 @@ def __init__(
             kwds.pop(key, None)
 
         kwds["dtype"] = ensure_dtype_objs(kwds.get("dtype", None))
-        try:
-            self._reader = parsers.TextReader(self.handles.handle, **kwds)
-        except Exception:
-            self.handles.close()
-            raise
+        self._reader = parsers.TextReader(src, **kwds)
 
         self.unnamed_cols = self._reader.unnamed_cols
 
@@ -196,9 +185,7 @@ def __init__(
         self._implicit_index = self._reader.leading_cols > 0
 
     def close(self) -> None:
-        super().close()
-
-        # close additional handles opened by C parser
+        # close handles opened by C parser
         try:
             self._reader.close()
         except ValueError:

pandas/io/parsers/python_parser.py

@@ -25,7 +25,6 @@
 import pandas._libs.lib as lib
 from pandas._typing import (
     ArrayLike,
-    FilePath,
     ReadCsvBuffer,
     Scalar,
 )
@@ -51,13 +50,11 @@
 
 
 class PythonParser(ParserBase):
-    def __init__(
-        self, f: FilePath | ReadCsvBuffer[bytes] | ReadCsvBuffer[str] | list, **kwds
-    ):
+    def __init__(self, f: ReadCsvBuffer[str] | list, **kwds):
         """
         Workhorse function for processing nested list into DataFrame
         """
-        ParserBase.__init__(self, kwds)
+        super().__init__(kwds)
 
         self.data: Iterator[str] | None = None
         self.buf: list = []
@@ -104,28 +101,18 @@ def __init__(
             # read_excel: f is a list
             self.data = cast(Iterator[str], f)
         else:
-            self._open_handles(f, kwds)
-            assert self.handles is not None
-            assert hasattr(self.handles.handle, "readline")
-            try:
-                self._make_reader(self.handles.handle)
-            except (csv.Error, UnicodeDecodeError):
-                self.close()
-                raise
+            assert hasattr(f, "readline")
+            self._make_reader(f)
 
         # Get columns in two steps: infer from data, then
         # infer column indices from self.usecols if it is specified.
         self._col_indices: list[int] | None = None
         columns: list[list[Scalar | None]]
-        try:
-            (
-                columns,
-                self.num_original_columns,
-                self.unnamed_cols,
-            ) = self._infer_columns()
-        except (TypeError, ValueError):
-            self.close()
-            raise
+        (
+            columns,
+            self.num_original_columns,
+            self.unnamed_cols,
+        ) = self._infer_columns()
 
         # Now self.columns has the set of columns that we will process.
         # The original set is stored in self.original_columns.
@@ -1259,9 +1246,7 @@ class FixedWidthFieldParser(PythonParser):
     See PythonParser for details.
     """
 
-    def __init__(
-        self, f: FilePath | ReadCsvBuffer[bytes] | ReadCsvBuffer[str], **kwds
-    ) -> None:
+    def __init__(self, f: ReadCsvBuffer[str], **kwds) -> None:
         # Support iterators, convert to a list.
         self.colspecs = kwds.pop("colspecs")
         self.infer_nrows = kwds.pop("infer_nrows")