gh-159422: Eagerly import warnings module to failure of GzipFile.__del__ during finalization

Lib/gzip.py

@@ -11,6 +11,7 @@
 import struct
 import sys
 import time
+import warnings  # must stay eager to support finalization
 import weakref
 import zlib
 from compression._common import _streams
@@ -229,7 +230,6 @@ def __init__(self, filename=None, mode=None,
 
             elif mode.startswith(('w', 'a', 'x')):
                 if origmode is None:
-                    import warnings
                     warnings.warn(
                         "GzipFile was opened for writing, but this will "
                         "change in future Python releases.  "
@@ -468,7 +468,6 @@ def readline(self, size=-1):
 
     def __del__(self):
         if self.mode == WRITE and not self.closed:
-            import warnings
             warnings.warn("unclosed GzipFile",
                           ResourceWarning, source=self, stacklevel=2)
 

Lib/test/test_gzip.py

@@ -965,6 +965,17 @@ def test_refloop_unraisable(self):
                 gc.collect()
                 self.assertIsNone(cm.unraisable)
 
+    @requires_subprocess()
+    def test_unclosed_at_shutdown(self):
+        rc, out, err = assert_python_ok("-c", f"""if 1:
+            import gzip
+            f = gzip.GzipFile({self.filename!r}, "wb")
+            f.write({data1!r})
+        """)
+        self.assertNotIn(b"Exception ignored", err)
+        with gzip.GzipFile(self.filename) as f:
+            self.assertEqual(f.read(), data1)
+
 
 class TestOpen(BaseTest):
     def test_binary_modes(self):

Misc/NEWS.d/next/Library/2026-10-14-15-50-59.gh-issue-159422.16mSqQ.rst

@@ -0,0 +1,4 @@
+:mod:`gzip` now imports :mod:`warnings` eagerly so that a writable
+:class:`~gzip.GzipFile` left unclosed at interpreter shutdown can emit its
+:exc:`ResourceWarning` and be closed instead of failing with an
+:exc:`ImportError`.