Mailman 3 March 2012 - Python-Dev

dictproxy for other mapping types than dict
by Victor Stinner March 22, 2012

March 22, 2012

Hi, I created the following issue to expose the dictproxy as a builtin type. http://bugs.python.org/issue14386 I would be interesting to accept any mapping type, not only dict. dictproxy implementation supports any mapping, even list or tuple, but I don't want to support sequences because a missing key would raise an IndexError instead of a KeyError. My problem is to check the type in C. issubclass(collections.ChainMap, collections.abc.Sequence) is False which is the expected result, so I … [View More]

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Re: [Python-Dev] Python-Dev Digest, Vol 104, Issue 79
by Peter Harris March 22, 2012

March 22, 2012

> > On 03/21/2012 07:39 PM, Huan Do wrote: > > *Hi, > > > > I am a graduating Berkeley student that loves python and would like to > > propose an enhancement to python. My proposal introduces a concept of > > slicing generator. For instance, if one does x[:] it returns a list > > which is a copy of x. Sometimes programmers would want to iterate over a > > slice of x, but they do not like the overhead of constructing another > > list. … [View More]

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New PEP
by Huan Do March 22, 2012

March 22, 2012

*Hi, I am a graduating Berkeley student that loves python and would like to propose an enhancement to python. My proposal introduces a concept of slicing generator. For instance, if one does x[:] it returns a list which is a copy of x. Sometimes programmers would want to iterate over a slice of x, but they do not like the overhead of constructing another list. Instead we can create a similar operator that returns a generator. My proposed syntax is x(:). The programmers are of course able to … [View More]

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[RELEASED] Python 3.3.0 alpha 1
by Georg Brandl March 21, 2012

March 21, 2012

On behalf of the Python development team, I'm happy to announce the first alpha release of Python 3.3.0. This is a preview release, and its use is not recommended in production settings. Python 3.3 includes a range of improvements of the 3.x series, as well as easier porting between 2.x and 3.x. Major new features in the 3.3 release series are: * PEP 380, Syntax for Delegating to a Subgenerator ("yield from") * PEP 393, Flexible String Representation (doing away with the distinction … [View More]

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GSoC 2012: Python Core Participation?
by martin＠v.loewis.de March 21, 2012

March 21, 2012

I'm wondering whether Python Core should participate in GSoC 2012 or not, as core contributors have shown little interest in acting as mentors in the past. If you are a core committer and volunteer as GSoC mentor for 2012, please let me know by Friday (March 23rd). Regards, Martin

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PEP 416: Add a frozendict builtin type
by Victor Stinner March 21, 2012

March 21, 2012

As requested, I create a PEP and a related issue: http://www.python.org/dev/peps/pep-0416/ http://bugs.python.org/issue14162 The PEP 416 is different from my previous propositions: frozendict values can be mutable and dict doesn't inherit from frozendict anymore. But it is still possible to use the PyDict C API on frozendict (which is more an implementation detail). TODO: - write the documentation - decide if new functions should be added to the C API, maybe a new PyFrozenDict_New() … [View More]function? (but would it take a mapping or a list of tuple?) -- PEP: 416 Title: Add a frozendict builtin type Version: $Revision$ Last-Modified: $Date$ Author: Victor Stinner <victor.stinner(a)gmail.com> Status: Draft Type: Standards Track Content-Type: text/x-rst Created: 29-February-2012 Python-Version: 3.3 Abstract ======== Add a new frozendict builtin type. Rationale ========= A frozendict mapping cannot be changed, but its values can be mutable (not hashable). A frozendict is hashable and so immutable if all values are hashable (immutable). Use cases of frozendict: * hashable frozendict can be used as a key of a mapping or as a member of set * frozendict helps optimization because the mapping is constant * frozendict avoids the need of a lock when the frozendict is shared by multiple threads or processes, especially hashable frozendict Constraints =========== * frozendict has to implement the Mapping abstract base class * frozendict keys and values can be unorderable * a frozendict is hashable if all keys and values are hashable * frozendict hash does not depend on the items creation order Implementation ============== * Add a PyFrozenDictObject structure based on PyDictObject with an extra "Py_hash_t hash;" field * frozendict.__hash__() is implemented using hash(frozenset(self.items())) and caches the result in its private hash attribute * Register frozendict has a collections.abc.Mapping * frozendict can be used with PyDict_GetItem(), but PyDict_SetItem() and PyDict_DelItem() raise a TypeError Recipe: immutable dict ====================== An immutable mapping can be implemented using frozendict:: import itertools class immutabledict(frozendict): def __new__(cls, *args, **kw): # ensure that all values are immutable for key, value in itertools.chain(args, kw.items()): if not isinstance(value, (int, float, complex, str, bytes)): hash(value) # frozendict ensures that all keys are immutable return frozendict.__new__(cls, *args, **kw) def __repr__(self): return 'immutabledict' + frozendict.__repr__(self)[10:] Objections ========== *namedtuple may fit the requiements of a frozendict.* A namedtuple is not a mapping, it does not implement the Mapping abstract base class. *frozendict can be implemented in Python using descriptors" and "frozendict just need to be practically constant.* If frozendict is used to harden Python (security purpose), it must be implemented in C. A type implemented in C is also faster. *The PEP 351 was rejected.* The PEP 351 tries to freeze an object and so may convert a mutable object to an immutable object (using a different type). frozendict doesn't convert anything: hash(frozendict) raises a TypeError if a value is not hashable. Freezing an object is not the purpose of this PEP. Links ===== * PEP 412: Key-Sharing Dictionary (`issue #13903 <http://bugs.python.org/issue13903>`_) * PEP 351: The freeze protocol * `The case for immutable dictionaries; and the central misunderstanding of PEP 351 <http://www.cs.toronto.edu/~tijmen/programming/immutableDictionaries.html>`_ * `Frozen dictionaries (Python recipe 414283) <http://code.activestate.com/recipes/414283-frozen-dictionaries/>`_ by Oren Tirosh Copyright ========= This document has been placed in the public domain. [View Less]

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Re: [Python-Dev] [Python-checkins] cpython: Issue #14328: Add keyword-only parameters to PyArg_ParseTupleAndKeywords.
by Benjamin Peterson March 20, 2012

March 20, 2012

2012/3/20 larry.hastings <python-checkins(a)python.org>: > http://hg.python.org/cpython/rev/052779d34945 > changeset: 75842:052779d34945 > parent: 75839:1c0058991740 > user: Larry Hastings <larry(a)hastings.org> > date: Tue Mar 20 20:06:16 2012 +0000 > summary: > Issue #14328: Add keyword-only parameters to PyArg_ParseTupleAndKeywords. > > They're optional-only for now (… [View More]

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pysandbox 1.5 released
by Victor Stinner March 20, 2012

March 20, 2012

pysandbox is a Python sandbox. By default, untrusted code executed in the sandbox cannot modify the environment (write a file, use print or import a module). But you can configure the sandbox to choose exactly which features are allowed or not, e.g. import sys module and read /etc/issue file. http://pypi.python.org/pypi/pysandbox https://github.com/haypo/pysandbox/ Main changes since pysandbox 1.0.3: - More modules and functions are allowed: math, random and time modules, and the compile() … [View More]

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regarding HTML mail
by Tshepang Lekhonkhobe March 20, 2012

March 20, 2012

apology: I searched for a few minutes and could not find a code of conduct regarding HTML mail. Can we have some guideline to allow only plain text emails, so as to avoid cases like http://mail.python.org/pipermail/docs/2012-March/007999.html, where you are forced to scroll horizontally in order to read the text.

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svn.python.org and buildbots down
by Stefan Krah March 19, 2012

March 19, 2012

Hello, you might be aware of it already. In case not, it appears that svn.python.org and the buildbots are down. Stefan Krah

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