bpo-39357: Remove buffering parameter of bz2.BZ2File (GH-18028)

Remove the buffering parameter of bz2.BZ2File. Since Python 3.0, it
was ignored and using it was emitting a DeprecationWarning. Pass an
open file object to control how the file is opened.

The compresslevel parameter becomes keyword-only.

2 files changed, 4 insertions, 9 deletions

diff --git a/Lib/bz2.py b/Lib/bz2.py
index 21e8ff4..a499ca3 100644
--- a/Lib/bz2.py
+++ b/Lib/bz2.py
@@ -24,8 +24,6 @@ _MODE_READ     = 1
 # Value 2 no longer used
 _MODE_WRITE    = 3
 
-_sentinel = object()
-
 
 class BZ2File(_compression.BaseStream):
 
@@ -38,7 +36,7 @@ class BZ2File(_compression.BaseStream):
     returned as bytes, and data to be written should be given as bytes.
     """
 
-    def __init__(self, filename, mode="r", buffering=_sentinel, compresslevel=9):
+    def __init__(self, filename, mode="r", *, compresslevel=9):
         """Open a bzip2-compressed file.
 
         If filename is a str, bytes, or PathLike object, it gives the
@@ -65,12 +63,6 @@ class BZ2File(_compression.BaseStream):
         self._closefp = False
         self._mode = _MODE_CLOSED
 
-        if buffering is not _sentinel:
-            warnings.warn("Use of 'buffering' argument is deprecated and ignored "
-                          "since Python 3.0.",
-                          DeprecationWarning,
-                          stacklevel=2)
-
         if not (1 <= compresslevel <= 9):
             raise ValueError("compresslevel must be between 1 and 9")
 
diff --git a/Lib/test/test_bz2.py b/Lib/test/test_bz2.py
index eb2f72e..030d564 100644
--- a/Lib/test/test_bz2.py
+++ b/Lib/test/test_bz2.py
@@ -100,6 +100,9 @@ class BZ2FileTest(BaseTest):
         self.assertRaises(ValueError, BZ2File, os.devnull, compresslevel=0)
         self.assertRaises(ValueError, BZ2File, os.devnull, compresslevel=10)
 
+        # compresslevel is keyword-only
+        self.assertRaises(TypeError, BZ2File, os.devnull, "r", 3)
+
     def testRead(self):
         self.createTempFile()
         with BZ2File(self.filename) as bz2f: