Issue #19222: Add support for the 'x' mode to the gzip module.

Original patch by Tim Heaney.

Doc/library/gzip.rst

@@ -35,8 +35,8 @@ The module defines the following items:
    :class:`bytes` object), or an existing file object to read from or write to.
 
    The *mode* argument can be any of ``'r'``, ``'rb'``, ``'a'``, ``'ab'``,
-   ``'w'``, or ``'wb'`` for binary mode, or ``'rt'``, ``'at'``, or ``'wt'`` for
-   text mode. The default is ``'rb'``.
+   ``'w'``, ``'wb'``, ``'x'`` or ``'xb'`` for binary mode, or ``'rt'``,
+   ``'at'``, ``'wt'``, or ``'xt'`` for text mode. The default is ``'rb'``.
 
    The *compresslevel* argument is an integer from 0 to 9, as for the
    :class:`GzipFile` constructor.
@@ -53,6 +53,9 @@ The module defines the following items:
       Added support for *filename* being a file object, support for text mode,
       and the *encoding*, *errors* and *newline* arguments.
 
+   .. versionchanged:: 3.4
+      Added support for the ``'x'``, ``'xb'`` and ``'xt'`` modes.
+
 
 .. class:: GzipFile(filename=None, mode=None, compresslevel=9, fileobj=None, mtime=None)
 
@@ -73,8 +76,9 @@ The module defines the following items:
    original filename is not included in the header.
 
    The *mode* argument can be any of ``'r'``, ``'rb'``, ``'a'``, ``'ab'``, ``'w'``,
-   or ``'wb'``, depending on whether the file will be read or written.  The default
-   is the mode of *fileobj* if discernible; otherwise, the default is ``'rb'``.
+   ``'wb'``, ``'x'``, or ``'xb'``, depending on whether the file will be read or
+   written.  The default is the mode of *fileobj* if discernible; otherwise, the
+   default is ``'rb'``.
 
    Note that the file is always opened in binary mode. To open a compressed file
    in text mode, use :func:`.open` (or wrap your :class:`GzipFile` with an
@@ -125,6 +129,9 @@ The module defines the following items:
    .. versionchanged:: 3.3
       The :meth:`io.BufferedIOBase.read1` method is now implemented.
 
+   .. versionchanged:: 3.4
+      Added support for the ``'x'`` and ``'xb'`` modes.
+
 
 .. function:: compress(data, compresslevel=9)
 

Lib/gzip.py

@@ -23,9 +23,9 @@ def open(filename, mode="rb", compresslevel=9,
     The filename argument can be an actual filename (a str or bytes object), or
     an existing file object to read from or write to.
 
-    The mode argument can be "r", "rb", "w", "wb", "a" or "ab" for binary mode,
-    or "rt", "wt" or "at" for text mode. The default mode is "rb", and the
-    default compresslevel is 9.
+    The mode argument can be "r", "rb", "w", "wb", "x", "xb", "a" or "ab" for
+    binary mode, or "rt", "wt", "xt" or "at" for text mode. The default mode is
+    "rb", and the default compresslevel is 9.
 
     For binary mode, this function is equivalent to the GzipFile constructor:
     GzipFile(filename, mode, compresslevel). In this case, the encoding, errors
@@ -151,11 +151,11 @@ class GzipFile(io.BufferedIOBase):
         fileobj, if discernible; otherwise, it defaults to the empty string,
         and in this case the original filename is not included in the header.
 
-        The mode argument can be any of 'r', 'rb', 'a', 'ab', 'w', or 'wb',
-        depending on whether the file will be read or written.  The default
+        The mode argument can be any of 'r', 'rb', 'a', 'ab', 'w', 'wb', 'x', or
+        'xb' depending on whether the file will be read or written.  The default
         is the mode of fileobj if discernible; otherwise, the default is 'rb'.
         A mode of 'r' is equivalent to one of 'rb', and similarly for 'w' and
-        'wb', and 'a' and 'ab'.
+        'wb', 'a' and 'ab', and 'x' and 'xb'.
 
         The compresslevel argument is an integer from 0 to 9 controlling the
         level of compression; 1 is fastest and produces the least compression,
@@ -201,7 +201,7 @@ class GzipFile(io.BufferedIOBase):
             self.min_readsize = 100
             fileobj = _PaddedFile(fileobj)
 
-        elif mode.startswith(('w', 'a')):
+        elif mode.startswith(('w', 'a', 'x')):
             self.mode = WRITE
             self._init_write(filename)
             self.compress = zlib.compressobj(compresslevel,

Lib/test/test_gzip.py

@@ -131,6 +131,14 @@ class TestGzip(BaseTest):
                 if not ztxt: break
         self.assertEqual(contents, b'a'*201)
 
+    def test_exclusive_write(self):
+        with gzip.GzipFile(self.filename, 'xb') as f:
+            f.write(data1 * 50)
+        with gzip.GzipFile(self.filename, 'rb') as f:
+            self.assertEqual(f.read(), data1 * 50)
+        with self.assertRaises(FileExistsError):
+            gzip.GzipFile(self.filename, 'xb')
+
     def test_buffered_reader(self):
         # Issue #7471: a GzipFile can be wrapped in a BufferedReader for
         # performance.
@@ -206,6 +214,9 @@ class TestGzip(BaseTest):
         self.test_write()
         with gzip.GzipFile(self.filename, 'r') as f:
             self.assertEqual(f.myfileobj.mode, 'rb')
+        support.unlink(self.filename)
+        with gzip.GzipFile(self.filename, 'x') as f:
+            self.assertEqual(f.myfileobj.mode, 'xb')
 
     def test_1647484(self):
         for mode in ('wb', 'rb'):
@@ -414,35 +425,59 @@ class TestGzip(BaseTest):
 class TestOpen(BaseTest):
     def test_binary_modes(self):
         uncompressed = data1 * 50
+
         with gzip.open(self.filename, "wb") as f:
             f.write(uncompressed)
         with open(self.filename, "rb") as f:
             file_data = gzip.decompress(f.read())
             self.assertEqual(file_data, uncompressed)
+
         with gzip.open(self.filename, "rb") as f:
             self.assertEqual(f.read(), uncompressed)
+
         with gzip.open(self.filename, "ab") as f:
             f.write(uncompressed)
         with open(self.filename, "rb") as f:
             file_data = gzip.decompress(f.read())
             self.assertEqual(file_data, uncompressed * 2)
 
+        with self.assertRaises(FileExistsError):
+            gzip.open(self.filename, "xb")
+        support.unlink(self.filename)
+        with gzip.open(self.filename, "xb") as f:
+            f.write(uncompressed)
+        with open(self.filename, "rb") as f:
+            file_data = gzip.decompress(f.read())
+            self.assertEqual(file_data, uncompressed)
+
     def test_implicit_binary_modes(self):
         # Test implicit binary modes (no "b" or "t" in mode string).
         uncompressed = data1 * 50
+
         with gzip.open(self.filename, "w") as f:
             f.write(uncompressed)
         with open(self.filename, "rb") as f:
             file_data = gzip.decompress(f.read())
             self.assertEqual(file_data, uncompressed)
+
         with gzip.open(self.filename, "r") as f:
             self.assertEqual(f.read(), uncompressed)
+
         with gzip.open(self.filename, "a") as f:
             f.write(uncompressed)
         with open(self.filename, "rb") as f:
             file_data = gzip.decompress(f.read())
             self.assertEqual(file_data, uncompressed * 2)
 
+        with self.assertRaises(FileExistsError):
+            gzip.open(self.filename, "x")
+        support.unlink(self.filename)
+        with gzip.open(self.filename, "x") as f:
+            f.write(uncompressed)
+        with open(self.filename, "rb") as f:
+            file_data = gzip.decompress(f.read())
+            self.assertEqual(file_data, uncompressed)
+
     def test_text_modes(self):
         uncompressed = data1.decode("ascii") * 50
         uncompressed_raw = uncompressed.replace("\n", os.linesep)
@@ -476,6 +511,8 @@ class TestOpen(BaseTest):
             gzip.open(123.456)
         with self.assertRaises(ValueError):
             gzip.open(self.filename, "wbt")
+        with self.assertRaises(ValueError):
+            gzip.open(self.filename, "xbt")
         with self.assertRaises(ValueError):
             gzip.open(self.filename, "rb", encoding="utf-8")
         with self.assertRaises(ValueError):

Misc/NEWS

@@ -54,8 +54,8 @@ Core and Builtins
 Library
 -------
 
-- Issues #19201, #19223: Add "x" mode (exclusive creation) in opening file to
-  bz2 and lzma modules. Patches by Tim Heaney and Vajrasky Kok.
+- Issues #19201, #19222, #19223: Add "x" mode (exclusive creation) in opening
+  file to bz2, gzip and lzma modules. Patches by Tim Heaney and Vajrasky Kok.
 
 - Fix a reference count leak in _sre.