Efficient python 2-d arrays?

[Jacob Biesinger]

On Thu, Jan 20, 2011 at 12:48 PM, Dan Stromberg <drsalists at gmail.com> wrote:
> On Thu, Jan 20, 2011 at 11:36 AM, Jake Biesinger
> <jake.biesinger at gmail.com> wrote:
>>> Thanks for the great suggestions!
>>
>> On a related note, is there no way to efficiently sort a python array?
>>
>>
>>>>> x = array('f', xrange(10000000))
>>>>> x.sort()
>> ---------------------------------------------------------------------------
>> AttributeError                            Traceback (most recent call last)
>>
>> /home/wbiesing/src/python-sort/<ipython console> in <module>()
>>
>> AttributeError: 'array.array' object has no attribute 'sort'
>>
>>>>> type(sorted(x))
>> <type 'list'>
>>
>> Seems like a common enough task, but no way to do it efficiently without scipy/numpy.
>
> Tap, tap: Is this thing on?  I keep sending messages to this list, but
> no one seems to "hear" what I'm writing.

Hey Dan, indeed thanks for the code; I pulled it down and played
around with timsort a while ago. Timsort is indeed a beast. My current
solution is to do an argsort.  Since I can't roll with your cython
implementations (pure python *only*), this seems a bit faster than
sorting the original two lists using a modified pure-python timsort.
Something along the lines of:

args = sorted(range(len(seq1)), key=seq1.__getitem__)
seq1 = [seq1[i] for i in args]
seq2 = [seq2[i] for i in args]

but the method suffers from a fairly high memory usage (big list of
int's for args).  If this barrier is too high, I will be switching
over to your pure-python timsort.

> Anyway, I have a bunch of sorts in python (pure or cython, your
> option) at http://stromberg.dnsalias.org/cgi-bin/viewvc.cgi/sorts/compare/trunk/?root=svn
>
> The pure python versions should all work out of the box with an
> array.array.  I tested the timsort on an array.array, and it worked
> well.

your pylint runs fail for me, saying you should use disable, not disable-msg.
pylint 0.23.0,
astng 0.21.1, common 0.54.0
Python 2.6.6 (r266:84292, Sep 15 2010, 16:22:56)
[GCC 4.4.5]

> Also, I just made a trivial modification (not checked in! ...but I did
> test it) to make the cythonized timsort support sorting arrays - just
> change the "list" type declarations to "object" (or perhaps
> "array.array") prior to compiling.

I'm not very familiar with cython syntax-- how do you bring in the array module?
cimport array? import array? I see you need to change cdef list to
cdef array.array or something like that.  Perhaps you could send a
diff?

Thanks!