From 6120739f0cb1c26069570fea701fe79489f1cd9d Mon Sep 17 00:00:00 2001
From: Ned Deily <nad@acm.org>
Date: Sun, 9 Mar 2014 14:44:34 -0700
Subject: Issue #20875: Prevent possible gzip "'read' is not defined"
 NameError. Patch by Claudiu Popa.

---
 Lib/gzip.py           | 2 +-
 Lib/test/test_gzip.py | 7 +++++++
 Misc/NEWS             | 3 +++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Lib/gzip.py b/Lib/gzip.py
index 2fd03fa..4ff9820 100644
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -99,7 +99,7 @@ class _PaddedFile:
             self._read -= len(prepend)
             return
         else:
-            self._buffer = self._buffer[read:] + prepend
+            self._buffer = self._buffer[self._read:] + prepend
         self._length = len(self._buffer)
         self._read = 0
 
diff --git a/Lib/test/test_gzip.py b/Lib/test/test_gzip.py
index c94d54e..034acb0 100644
--- a/Lib/test/test_gzip.py
+++ b/Lib/test/test_gzip.py
@@ -396,6 +396,13 @@ class TestGzip(BaseTest):
         with gzip.GzipFile(fileobj=io.BytesIO(gzdata)) as f:
             self.assertEqual(f.read(), b'Test')
 
+    def test_prepend_error(self):
+        # See issue #20875
+        with gzip.open(self.filename, "wb") as f:
+            f.write(data1)
+        with gzip.open(self.filename, "rb") as f:
+            f.fileobj.prepend()
+
 class TestOpen(BaseTest):
     def test_binary_modes(self):
         uncompressed = data1 * 50
diff --git a/Misc/NEWS b/Misc/NEWS
index d0aec17..7baa0f7 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -13,6 +13,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #20875: Prevent possible gzip "'read' is not defined" NameError.
+  Patch by Claudiu Popa.
+
 - Issue #20283: RE pattern methods now accept the string keyword parameters
   as documented.  The pattern and source keyword parameters are left as
   deprecated aliases.
-- 
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