[Python-checkins] bpo-34898: Add mtime parameter to gzip.compress(). (GH-9704)

Serhiy Storchaka webhook-mailer at python.org
Wed Nov 7 04:50:37 EST 2018

commit: 0e7497cb469b003a45a4abe4105b81ef6d0c4002
branch: master
author: guoci <zguoci at gmail.com>
committer: Serhiy Storchaka <storchaka at gmail.com>
date: 2018-11-07T11:50:23+02:00

bpo-34898: Add mtime parameter to gzip.compress(). (GH-9704)

Without setting mtime, time.time() will be used as the timestamp which will
end up in the compressed data and each invocation of the compress() function
will vary over time.

A Misc/NEWS.d/next/Library/2018-10-04-17-23-43.bpo-34898.Wo2PoJ.rst
M Doc/library/gzip.rst
M Doc/whatsnew/3.8.rst
M Lib/gzip.py
M Lib/test/test_gzip.py

diff --git a/Doc/library/gzip.rst b/Doc/library/gzip.rst
index a57307b0e499..8850a33f4abb 100644
--- a/Doc/library/gzip.rst
+++ b/Doc/library/gzip.rst
@@ -157,13 +157,15 @@ The module defines the following items:
       Accepts a :term:`path-like object`.
-.. function:: compress(data, compresslevel=9)
+.. function:: compress(data, compresslevel=9, *, mtime=None)
    Compress the *data*, returning a :class:`bytes` object containing
-   the compressed data.  *compresslevel* has the same meaning as in
+   the compressed data.  *compresslevel* and *mtime* have the same meaning as in
    the :class:`GzipFile` constructor above.
    .. versionadded:: 3.2
+   .. versionchanged:: 3.8
+      Added the *mtime* parameter for reproducible output.
 .. function:: decompress(data)
diff --git a/Doc/whatsnew/3.8.rst b/Doc/whatsnew/3.8.rst
index 2d3a116df9d3..51aee1bed835 100644
--- a/Doc/whatsnew/3.8.rst
+++ b/Doc/whatsnew/3.8.rst
@@ -131,6 +131,13 @@ asyncio
 On Windows, the default event loop is now :class:`~asyncio.ProactorEventLoop`.
+Added the *mtime* parameter to :func:`gzip.compress` for reproducible output.
+(Contributed by Guo Ci Teo in :issue:`34898`.)
 idlelib and IDLE
diff --git a/Lib/gzip.py b/Lib/gzip.py
index 151ff1405b16..948fec293e23 100644
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -520,12 +520,12 @@ def _rewind(self):
         self._new_member = True
-def compress(data, compresslevel=_COMPRESS_LEVEL_BEST):
+def compress(data, compresslevel=_COMPRESS_LEVEL_BEST, *, mtime=None):
     """Compress data in one shot and return the compressed string.
     Optional argument is the compression level, in range of 0-9.
     buf = io.BytesIO()
-    with GzipFile(fileobj=buf, mode='wb', compresslevel=compresslevel) as f:
+    with GzipFile(fileobj=buf, mode='wb', compresslevel=compresslevel, mtime=mtime) as f:
     return buf.getvalue()
diff --git a/Lib/test/test_gzip.py b/Lib/test/test_gzip.py
index 1e8b41f07b3e..2c8f854c6436 100644
--- a/Lib/test/test_gzip.py
+++ b/Lib/test/test_gzip.py
@@ -499,6 +499,17 @@ def test_compress(self):
                 with gzip.GzipFile(fileobj=io.BytesIO(datac), mode="rb") as f:
                     self.assertEqual(f.read(), data)
+    def test_compress_mtime(self):
+        mtime = 123456789
+        for data in [data1, data2]:
+            for args in [(), (1,), (6,), (9,)]:
+                with self.subTest(data=data, args=args):
+                    datac = gzip.compress(data, *args, mtime=mtime)
+                    self.assertEqual(type(datac), bytes)
+                    with gzip.GzipFile(fileobj=io.BytesIO(datac), mode="rb") as f:
+                        f.read(1) # to set mtime attribute
+                        self.assertEqual(f.mtime, mtime)
     def test_decompress(self):
         for data in (data1, data2):
             buf = io.BytesIO()
diff --git a/Misc/ACKS b/Misc/ACKS
index 89fb0c7000b4..aba60945a1e2 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1615,6 +1615,7 @@ Monty Taylor
 Anatoly Techtonik
 Martin Teichmann
 Gustavo Temple
+Guo Ci Teo
 Mikhail Terekhov
 Victor Terrón
 Pablo Galindo
diff --git a/Misc/NEWS.d/next/Library/2018-10-04-17-23-43.bpo-34898.Wo2PoJ.rst b/Misc/NEWS.d/next/Library/2018-10-04-17-23-43.bpo-34898.Wo2PoJ.rst
new file mode 100644
index 000000000000..4c0a061daf9f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-10-04-17-23-43.bpo-34898.Wo2PoJ.rst
@@ -0,0 +1,2 @@
+Add `mtime` argument to `gzip.compress` for reproducible output.
+Patch by Guo Ci Teo.
\ No newline at end of file

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