date:20110509

[Python-Dev] Commit changelog: issue number and merges

2011-05-09 Thread Victor Stinner

Hi,

Commit changelogs are important to understand why the code was changed.
I regulary use hg blame to search which commit introduced a particular
line of code, and I am always happy if I can find an issue number
because it usually contains the whole story.

And since the migration to Mercurial, we have also a great tool adding a
comment to an issue if the changelog contains an issue number (e.g.
changelog starting with Issue #11: ...). So if someone watchs an
issue (is in the nosy list), (s)he will be noticed that a related commit
was pushed. It is not exactly something new: we already do that with
Subversion except that today it is more automatic.

I noticed that some recent commits don't contain the issue number:
please try to always prefix your changelog with the issue number. It is
not mandatory, but it helps me when I dig the Python history.

--

For merge commits: many developers just write merge or merge 3.1. I
have to go to the parent commit (and something to the grandparent,
3.1-3.2-3.3) to learn more about the commit.

Would it be possible to repeat the changelog of the original commit in
the merge commits? svnmerge toold prepared a nice changelog containing
the changelog of all pendings commits, even when a commit was blocked.

For a merge commit, I copy/paste the changelog of the original commit
and I add a (Merge 3.1)  prefix. I prefer to add explictly a prefix
because it is not easy to notice that it is a merge commit in a
python-checkins email or in the history of hg.python.org.

We need maybe new tools to help the process.

--

Usecases needing better changelogs:

 - All changes section of a buildbot build
 - hg blame (or just hg log)

Victor

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Re: [Python-Dev] Commit changelog: issue number and merges

2011-05-09 Thread R. David Murray

On Mon, 09 May 2011 12:32:48 +0200, Victor Stinner 
victor.stin...@haypocalc.com wrote:
 For merge commits: many developers just write merge or merge 3.1. I
 have to go to the parent commit (and something to the grandparent,
 3.1-3.2-3.3) to learn more about the commit.
 
 Would it be possible to repeat the changelog of the original commit in
 the merge commits? svnmerge toold prepared a nice changelog containing
 the changelog of all pendings commits, even when a commit was blocked.
 
 For a merge commit, I copy/paste the changelog of the original commit
 and I add a (Merge 3.1)  prefix. I prefer to add explictly a prefix
 because it is not easy to notice that it is a merge commit in a
 python-checkins email or in the history of hg.python.org.

+1.  What I do is, in the edit window for the commit message, I pull
in .hg/last-message.txt, and just type 'Merge' in front of my previous
first line.  I don't add the merge-from number, because I figure if you
know which branch you are looking at you know which branch the merge
came from, given that there is a strict progression.

--
R. David Murray   http://www.bitdance.com
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Re: [Python-Dev] [Python-checkins] cpython (2.7): Issue #11277: Remove useless test from test_zlib.

2011-05-09 Thread Jim Jewett

Can you clarify (preferably in the commit message as well) exactly
*why* these largefile tests are useless?  For example, is there
another test that covers this already?

-jJ

On 5/7/11, nadeem.vawda python-check...@python.org wrote:
 http://hg.python.org/cpython/rev/201dcfc56e86
 changeset:   69886:201dcfc56e86
 branch:  2.7
 parent:  69881:a0147a1f1776
 user:Nadeem Vawda nadeem.va...@gmail.com
 date:Sat May 07 11:28:03 2011 +0200
 summary:
   Issue #11277: Remove useless test from test_zlib.

 files:
   Lib/test/test_zlib.py |  42 ---
   1 files changed, 0 insertions(+), 42 deletions(-)


 diff --git a/Lib/test/test_zlib.py b/Lib/test/test_zlib.py
 --- a/Lib/test/test_zlib.py
 +++ b/Lib/test/test_zlib.py
 @@ -72,47 +72,6 @@
   zlib.crc32('spam',  (2**31)))


 -# Issue #11277 - check that inputs of 2 GB (or 1 GB on 32 bits system) are
 -# handled correctly. Be aware of issues #1202. We cannot test a buffer of 4
 GB
 -# or more (#8650, #8651 and #10276), because the zlib stores the buffer
 size
 -# into an int.
 -class ChecksumBigBufferTestCase(unittest.TestCase):
 -if sys.maxsize  _4G:
 -# (64 bits system) crc32() and adler32() stores the buffer size
 into an
 -# int, the maximum filesize is INT_MAX (0x7FFF)
 -filesize = 0x7FFF
 -else:
 -# (32 bits system) On a 32 bits OS, a process cannot usually
 address
 -# more than 2 GB, so test only 1 GB
 -filesize = _1G
 -
 -@unittest.skipUnless(mmap, mmap() is not available.)
 -def test_big_buffer(self):
 -if sys.platform[:3] == 'win' or sys.platform == 'darwin':
 -requires('largefile',
 - 'test requires %s bytes and a long time to run' %
 - str(self.filesize))
 -try:
 -with open(TESTFN, wb+) as f:
 -f.seek(self.filesize-4)
 -f.write(asdf)
 -f.flush()
 -m = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ)
 -try:
 -if sys.maxsize  _4G:
 -self.assertEqual(zlib.crc32(m), 0x709418e7)
 -self.assertEqual(zlib.adler32(m), -2072837729)
 -else:
 -self.assertEqual(zlib.crc32(m), 722071057)
 -self.assertEqual(zlib.adler32(m), -1002962529)
 -finally:
 -m.close()
 -except (IOError, OverflowError):
 -raise unittest.SkipTest(filesystem doesn't have largefile
 support)
 -finally:
 -unlink(TESTFN)
 -
 -
  class ExceptionTestCase(unittest.TestCase):
  # make sure we generate some expected errors
  def test_badlevel(self):
 @@ -595,7 +554,6 @@
  def test_main():
  run_unittest(
  ChecksumTestCase,
 -ChecksumBigBufferTestCase,
  ExceptionTestCase,
  CompressTestCase,
  CompressObjectTestCase

 --
 Repository URL: http://hg.python.org/cpython

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[Python-Dev] more timely detection of unbound locals

2011-05-09 Thread Eli Bendersky

Hi all,

It's a known Python gotcha (*) that the following code:

x = 5
def foo():
print(x)
x = 1
print(x)
foo()

Will throw:

UnboundLocalError: local variable 'x' referenced before assignment

On the usage of 'x' in the *first* print. Recently, while reading the
zillionth question on StackOverflow on some variation of this case, I
started thinking whether this behavior is desired or just an implementation
artifact.

IIUC, the reason it behaves this way is that the symbol table logic goes
over the code before the code generation runs, sees the assignment 'x = 1`
and marks 'x' as local in foo. Then, the code generator generates LOAD_FAST
for all loads of 'x' in 'foo', even though 'x' is actually bound locally
after the first print. When the bytecode is run, since it's LOAD_FAST and no
store was made into the local 'x', ceval.c then throws the exception.

On first sight, it's possible to signal that 'x' truly becomes local only
after it's bound in the scope (and before that LOAD_NAME can be generated
for it instead of LOAD_FAST). To do this, some modifications to the symbol
table creation and usage are required, because we can no longer say x is
local in this block, but rather should attach scope information to each
instance of x. This has some overhead, but it's only at the compilation
stage so it shouldn't have a real effect on the runtime of Python code. This
is also less convenient and clean than the current approach - this is why
I'm wondering whether the behavior is an artifact of the implementation.

Would it not be worth to make Python's behavior more expected in this case,
at the cost of some implementation complexity? What are the cons to making
such a change? At least judging by the amount of people getting confused by
it, maybe it's in line with the zen of Python to behave more explicitly
here.

Thanks in advance,
Eli

(*) Variation of this FAQ:
http://docs.python.org/faq/programming.html#why-am-i-getting-an-unboundlocalerror-when-the-variable-has-a-value
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