From: Jeremy Hylton email@example.com
Subject: Python 2.1 alpha 2 released
Fri, 2 Feb 2001 18:40:08 -0500 (EST)
While Guido is working the press circuit at the LinuxWorld Expo in
New York City, the Python developers, including the many volunteers
and the folks from PythonLabs, were busy finishing the second alpha
release of Python 2.1.
The release is currently available from SourceForge and will
also be available from python.org later today. You can find the
source release at:
Please give it a good try! The only way Python 2.1 can become a
rock-solid product is if people test the alpha releases. If you are
using Python for demanding applications or on extreme platforms, we
are particularly interested in hearing your feedback. Are you
embedding Python or using threads? Please test your application
using Python 2.1a2! Please submit all bug reports through
- Scopes nest. If a name is used in a function or class, but is
not local, the definition in the nearest enclosing function scope
will be used. One consequence of this change is that lambda
statements could reference variables in the namespaces where the
lambda is defined. In some unusual cases, this change will break
In all previous version of Python, names were resolved in
exactly three namespaces -- the local namespace, the global
namespace, and the builtin namespace. According to this old
definition, if a function A is defined within a function B, the
names bound in B are not visible in A. The new rules make names
bound in B visible in A, unless A contains a name binding that
hides the binding in B.
Section 4.1 of the reference manual describes the new scoping
rules in detail. The test script in Lib/test/test_scope.py
demonstrates some of the effects of the change.
The new rules will cause existing code to break if it defines
nested functions where an outer function has local variables with
the same name as globals or builtins used by the inner function.
Under the old rules, the name str in helper() is bound to the
builtin function str(). Under the new rules, it will be bound to
the argument named str and an error will occur when helper() is
- The compiler will report a SyntaxError if "from ... import *"
occurs in a function or class scope. The language reference has
documented that this case is illegal, but the compiler never
checked for it. The recent introduction of nested scope makes the
meaning of this form of name binding ambiguous. In a future
release, the compiler may allow this form when there is no
possibility of ambiguity.
- repr(string) is easier to read, now using hex escapes instead
of octal, and using \t, \n and \r instead of \011, \012 and \015
>>> "\texample \r\n" + chr(0) + chr(255)
'\texample \r\n\x00\xff' # in 2.1
'\011example \015\012\000\377' # in 2.0
- Functions are now compared and hashed by identity, not by value,
since the func_code attribute is writable.
- Weak references (PEP 205) have been added. This involves a few
changes in the core, an extension module (_weakref), and a Python
module (weakref). The weakref module is the public interface. It
includes support for "explicit" weak references, proxy objects, and
mappings with weakly held values.
- A 'continue' statement can now appear in a try block within
the body of a loop. It is still not possible to use continue in a
- mailbox.py now has a new class, PortableUnixMailbox which is
identical to UnixMailbox but uses a more portable scheme for
determining From_ separators. Also, the constructors for all the
classes in this module have a new optional `factory' argument,
which is a callable used when new message classes must be
instantiated by the next() method.
- random.py is now self-contained, and offers all the
functionality of the now-deprecated whrandom.py. See the docs for
details. random.py also supports new functions getstate() and
setstate(), for saving and restoring the internal state of the
generator; and jumpahead(n), for quickly forcing the internal state
to be the same as if n calls to random() had been made. The latter
is particularly useful for multi- threaded programs, creating one
instance of the random.Random() class for each thread, then using
.jumpahead() to force each instance to use a non-overlapping
segment of the full period.
- random.py's seed() function is new. For bit-for-bit
compatibility with prior releases, use the whseed function instead.
The new seed function addresses two problems: (1) The old function
couldn't produce more than about 2**24 distinct internal states;
the new one about 2**45 (the best that can be done in the
Wichmann-Hill generator). (2) The old function sometimes produced
identical internal states when passed distinct integers, and there
was no simple way to predict when that would happen; the new one
guarantees to produce distinct internal states for all arguments in
- The socket module now supports raw packets on Linux. The
socket family is AF_PACKET.
- test_capi.py is a start at running tests of the Python C API.
The tests are implemented by the new Modules/_testmodule.c.
- A new extension module, _symtable, provides provisional access
to the internal symbol table used by the Python compiler. A
higher-level interface will be added on top of _symtable in a
- Build procedure: the zlib project is built in a different way
that ensures the zlib header files used can no longer get out of
synch with the zlib binary used. See PCbuild\readme.txt for
details. Your old zlib-related directories can be deleted; you'll
need to download fresh source for zlib and unpack it into a new
- Build: New subproject _test for the benefit of test_capi.py
- Build: subproject ucnhash is gone, since the code was folded
into the unicodedata subproject.
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