TYP: to_csv accepts IO[bytes] and fix FilePathOrBuffer (#41903)

Author: twoertwein

pandas/_typing.py

@@ -170,8 +170,8 @@
 
 # filenames and file-like-objects
 Buffer = Union[IO[AnyStr], RawIOBase, BufferedIOBase, TextIOBase, TextIOWrapper, mmap]
-FileOrBuffer = Union[str, Buffer[T]]
-FilePathOrBuffer = Union["PathLike[str]", FileOrBuffer[T]]
+FileOrBuffer = Union[str, Buffer[AnyStr]]
+FilePathOrBuffer = Union["PathLike[str]", FileOrBuffer[AnyStr]]
 
 # for arbitrary kwargs passed during reading/writing files
 StorageOptions = Optional[Dict[str, Any]]

pandas/core/generic.py

@@ -11,6 +11,7 @@
 from typing import (
     TYPE_CHECKING,
     Any,
+    AnyStr,
     Callable,
     Hashable,
     Mapping,
@@ -3295,7 +3296,7 @@ def to_latex(
     @doc(storage_options=_shared_docs["storage_options"])
     def to_csv(
         self,
-        path_or_buf: FilePathOrBuffer | None = None,
+        path_or_buf: FilePathOrBuffer[AnyStr] | None = None,
         sep: str = ",",
         na_rep: str = "",
         float_format: str | None = None,

pandas/io/formats/csvs.py

@@ -9,6 +9,7 @@
 from typing import (
     TYPE_CHECKING,
     Any,
+    AnyStr,
     Hashable,
     Iterator,
     Sequence,
@@ -48,7 +49,7 @@ class CSVFormatter:
     def __init__(
         self,
         formatter: DataFrameFormatter,
-        path_or_buf: FilePathOrBuffer[str] = "",
+        path_or_buf: FilePathOrBuffer[AnyStr] = "",
         sep: str = ",",
         cols: Sequence[Hashable] | None = None,
         index_label: IndexLabel | None = None,

pandas/io/formats/format.py

@@ -19,6 +19,7 @@
     IO,
     TYPE_CHECKING,
     Any,
+    AnyStr,
     Callable,
     Hashable,
     Iterable,
@@ -1054,7 +1055,7 @@ def to_string(
 
     def to_csv(
         self,
-        path_or_buf: FilePathOrBuffer[str] | None = None,
+        path_or_buf: FilePathOrBuffer[AnyStr] | None = None,
         encoding: str | None = None,
         sep: str = ",",
         columns: Sequence[Hashable] | None = None,