Mailman 3 August 2010 - NumPy-Discussion

ANN: NumPy 1.5.0 beta 2
by Ralf Gommers Aug. 19, 2010

Aug. 19, 2010

I am pleased to announce the availability of the second beta of NumPy 1.5.0. This will be the first NumPy release to include support for Python 3, as well as for Python 2.7. Please try this beta and report any problems on the NumPy mailing list. Especially with Python 3 testing will be very useful. On Linux and OS X building from source should be straightforward, for Windows a binary installer is provided. There is one important known issue on Windows left, in fromfile and tofile (ticket 1583). Binaries, sources and release notes can be found at https://sourceforge.net/projects/numpy/files/ Enjoy, Ralf

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Problem with loadtxt
by Scott MacDonald Aug. 18, 2010

Aug. 18, 2010

Hi, I have a text file called 'blah' that contains only the following line: 5399354557888517312,5399354557888517312 I want to load these into a numpy array as unit64's. The following script demonstrates my problem: import numpy as np with open('blah', 'r') as f: x = np.loadtxt(f, delimiter=',', dtype=(np.uint64, np.uint64)) with open('blah', 'r') as f: for line in f: print line print x The output I get is: 5399354557888517312,5399354557888517312 [5399354557888517120 5399354557888517120] Am I doing something wrong? Thanks for your help, Scott

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fancy indexing question
by Angus McMorland Aug. 18, 2010

Aug. 18, 2010

Hi all, I'm having a bit of a brain block about the following fancy indexing question, and am hoping someone can point me in the right direction. I have a 3-d array `a` that I want to reorder along its 0th dimension differently for each 1st dimension, with the indices given in a 2-d array `ord`. I can achieve this as follows a = np.random.randint(10, size=(4,3,2)) ord = np.array([[3,2,1,0],[0,2,1,3],[3,0,2,1]]).T b = a[ord][:,np.eye(3, dtype=bool),:] but it seems like it should be possible to do this in one indexing step and avoid the intermediate and the eye call. Any suggestions gratefully received. Thanks, Angus. -- AJC McMorland Post-doctoral research fellow Neurobiology, University of Pittsburgh

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Seeking advice on crowded namespace.
by Charles R Harris Aug. 18, 2010

Aug. 18, 2010

Hi All, I just added support for Legendre polynomials to numpy and I think the numpy.polynomial name space is getting a bit crowded. Since most of the current functions in that namespace are just used to implement the Polynomial, Chebyshev, and Legendre classes I'm thinking of only importing those classes by default and leaving the other functions to explicit imports. Of course I will have to fix the examples and maybe some other users will be inconvenienced by the change. But with 2.0.0 in the works this might be a good time to do this. Thoughts? Chuck

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add NPY_UNUSED to _import_{array|umath}
by Lisandro Dalcin Aug. 18, 2010

Aug. 18, 2010

When using gcc -Wall, the warnings below are common when including NumPy headers (e.g. Cython testsuite) /usr/lib64/python2.6/site-packages/numpy/core/include/numpy/__multiarray_api.h:968: warning: ‘_import_array’ defined but not used /usr/lib64/python2.6/site-packages/numpy/core/include/numpy/__ufunc_api.h:182: warning: ‘_import_umath’ defined but not used Any chance these functions could be decorated with the NPY_UNUSED() macro ? -- Lisandro Dalcin --------------- CIMEC (INTEC/CONICET-UNL) Predio CONICET-Santa Fe Colectora RN 168 Km 472, Paraje El Pozo Tel: +54-342-4511594 (ext 1011) Tel/Fax: +54-342-4511169

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longdouble (float96) literals
by Colin Macdonald Aug. 18, 2010

Aug. 18, 2010

How can I enter longdouble (float96) literals into my python/numpy programs? In C, I would postfix such numbers with 'L', but this gives a SyntaxError in python. The rest of my message is just two examples of what I'm talking about in case its not clear. Thanks, Colin ---------------------------------------------------------- Note: longdouble: machine epsilon of approx 1e-19 float64: mach eps approx 1e-16 For example, say I need a longdouble accurate 0.4 in my code: In [249]: f96 = numpy.longdouble In [250]: f96(0.4) * f96(10) - f96(4) Out[250]: 2.2204460492503130808e-16 # no, that converted 0.4 to a float64 first (and note the answer is machine epsilon for float64) In [251]: f96("0.4") * f96(10) - f96(4) Out[251]: 2.2204460492503130808e-16 # no In [252]: (f96(4)/f96(10)) * f96(10) - f96(4) Out[252]: 0.0 # this works (in this particular case). I also would've been happy with 1e-19 in the last case---of course I don't expect it to be exactly zero. Finally, here's another example involving pi, done without ipython: import numpy as np f96 = np.longdouble # of course this won't work because numpy.pi is a float64 mypi0 = f96(np.pi) print np.sin(mypi0) # in C, I would write: #mypi1 = 3.141592653589793238462643383279L mypi1 = 3.141592653589793238462643383279 print np.sin(mypi1) mypi2 = np.arctan2( f96(0), f96(-1) ) print np.sin(mypi2) OUTPUT: $ python f96_issue.py 1.22460635382e-16 1.22460635382e-16 -5.42101086243e-20 -- Colin Macdonald University Lecturer in Numerical Methodologies Tutorial Fellow at Oriel College University of Oxford

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clip applied to complex gives unexpected results
by Neal Becker Aug. 18, 2010

Aug. 18, 2010

The results of clip applied to complex values is surprising and not documented (AFAICT)

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Re: [Numpy-discussion] [SciPy-Dev] Good-bye, sort of (John Hunter)
by David Goldsmith Aug. 18, 2010

Aug. 18, 2010

> > After several years now of writing Python and now having written my first > > on-the-job 15 operational MATLAB LOC, all of which are string, cell > array, > > and file processing, I'm ready to say: "MATLAB: what a PITA!" :-( > > Ahh, cell arrays, they bring back memories. Makes you pine for a > dictionary, no? > > JDH Not to mention writeline, readline, string concatenation using +, English wording of loops, list comprehension, etc., etc., etc. - if people only knew... DG > -- > Privacy is overrated; Identity isn't.

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Find insertion point
by Nikolaus Rath Aug. 17, 2010

Aug. 17, 2010

Hello, I want to find the first i such that x[i] < y and x[i+1] >= y. Is there a way to do this without using a Python loop? I can't use np.searchsorted(), because my x array crosses y several times. Best, -Nikolaus -- »Time flies like an arrow, fruit flies like a Banana.« PGP fingerprint: 5B93 61F8 4EA2 E279 ABF6 02CF A9AD B7F8 AE4E 425C

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array manipulation
by Alex Ter-Sarkissov Aug. 17, 2010

Aug. 17, 2010

hi, this is probably a very silly question, but I can't get my hear around it unfortunately( I have an array (say, mat=rand(3,5)) from which I 'pull out' a row (say, s1=mat[1,]). The problem is, the shape of this row s1 is not [1,5], as I would expect, but rather [5,], which means that I can't, for example, concateante mat and s1 rowwise. thanks for the help

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