Mailman 3 February 2010 - NumPy-Discussion

Efficiently converting numpy record array to a list of dictionary
by Vishal Rana 05 Feb '10

05 Feb '10

How do I convert the numpy record array below: recs = [('Bill', 31, 260.0), ('Fred', 15, 145.0)] r = rec.fromrecords(recs, names='name, age, weight', formats='S30, i2, f4') to a list of dictionary like: [{'name': 'Bill', 'age': 31, 'weight': 260.0}, 'name': 'Fred', 'age': 15, 'weight': 145.0}]

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Unexpected tofile() behavior
by Jeffery Kline 05 Feb '10

05 Feb '10

I am experiencing unexpected behavior with the tofile() function. I try to write two files with but distinct names, but only one of the files is written. The following code illustrates. For me, it only writes the file 't.bin'. from numpy import * t=arange(0,1,0.1) T=arange(0,1,0.1) t.tofile('t.bin') T.tofile('T.bin') Meanwhile, the following code works as I expect by writing 't.bin' and 'S.bin': from numpy import * t=arange(0,1,0.1) T=arange(0,1,0.1) t.tofile('t.bin') T.tofile('S.bin') Am I doing something stupid or overlooking something obvious? My system is Mac os x 10.6.2, running python 2.6.4. Jeff

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multiply a lign matrix with a column matrix should return a scalar( matlab yes, numpy no)!!!
by laurent.feron＠free.fr 04 Feb '10

04 Feb '10

Hello, if i multiply two matrix, one with a unique line and the second one with a unique column, i should have a scalar: >>> line matrix([[1, 3, 1]]) >>> col matrix([[2], [2], [2]]) >>> line*col matrix([[10]]) Matlab give me a scalar, Numpy does not... Do you know why? Regards, Laurent

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Determine if numpy is installed from an extension
by Peter Notebaert 04 Feb '10

04 Feb '10

Hello, I have written a C-extension for python that uses arrays from python, does calculations on them and returns a result on that. I have now also added the possibility to provide numpy arrays. However this is not a requirement. Python arrays (lists) are still allowed also. I check in the C-code which kind of arrays are provided. That all works ok, but I have one problem. In the initialisation function for the extension I call import_array to initialise the numpy library. The problem is if numpy is not installed on the system, that this call generates a message and an error and the rest of the routine is aborted. Via the source code of numpy I discovered that import_array is in fact a macro that calls _import_array and checks its return value to give the message. But even it I call _import_array myself and check for the return code, after the initialisation routine has finished I still get the message 'No module named numpy.core.multiarray'. How can I test if numpy is installed on the system from the extension so that I do not active the numpy functionality and that it is still able to use my extension, but then without numpy support? I have searched in the manual and documentation, searched in google, but I do not find an answer on that question.

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[ANN] New package for manipulating labeled arrays
by Keith Goodman 04 Feb '10

04 Feb '10

I am pleased to announce the first release of the la package, version 0.1. The main class of the la package is a labeled array, larry. A larry consists of a data array and a label list. The data array is stored as a NumPy array and the label list as a list of lists. larry has built-in methods such as movingsum, ranking, merge, shuffle, zscore, demean, lag as well as typical Numpy methods like sum, max, std, sign, clip. NaNs are treated as missing data. Alignment by label is automatic when you add (or subtract, multiply, divide) two larrys. larry adds the convenience of labels, provides many built-in methods, and let's you use your existing array functions. Download: https://launchpad.net/larry/+download docs http://larry.sourceforge.net code https://launchpad.net/larry list http://groups.google.ca/group/pystatsmodels

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numpy.left_shift with negative x2
by markus.proeller＠ifm.com 04 Feb '10

04 Feb '10

Hello, the following operation seems strange to me >>> np.left_shift(2,-1) 0 I would have expected a right_shift by one. The documentation on http://docs.scipy.org/doc/numpy/reference/generated/numpy.left_shift.html#n… also says that the operation is equivalent to multiplying x1 by 2**x2. That's not the case! Markus

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np.bincount raises MemoryError when given an empty array
by Ernest Adrogué 02 Feb '10

02 Feb '10

Hello, Consider the following code: for j in range(5): f = np.bincount(x[y == j]) It fails with MemoryError whenever y == j is all False element-wise. In [96]: np.bincount([]) --------------------------------------------------------------------------- MemoryError Traceback (most recent call last) /home/ernest/<ipython console> in <module>() MemoryError: In [97]: np.__version__ Out[97]: '1.3.0' Is this a bug? Bye.

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Normalized histogram for data ranges 0 .. 1 returns PDF > 1
by Manos Tsagias 02 Feb '10

02 Feb '10

Hi all, I'm using numpy.histogram with normed=True with 1D data ranging 0 .. 1. The results return probabilities greater than 1. The trapezoidal integral returns 1, but I'm afraid this is due to the bin assigned values. Example follows: >>> from numpy import * >>> a = arange(0, 1, 0.1) >>> histogram(a, normed=True) (array([ 1.11111111, 1.11111111, 1.11111111, 1.11111111, 1.11111111, 1.11111111, 1.11111111, 1.11111111, 1.11111111, 1.11111111]), array([ 0. , 0.09, 0.18, 0.27, 0.36, 0.45, 0.54, 0.63, 0.72, 0.81, 0.9 ])) Is that normal? If not, does anyone encountered that before? Ideas welcome! Thanks, Manos._

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which Python for OS X to build installers?
by Ralf Gommers 01 Feb '10

01 Feb '10

Hi, With only a few changes (see diff below) to pavement.py I managed to build a dmg installer. For this I used the Python in the bootstrap virtualenv however, instead of the one in /Library/Frameworks/Python.framework/. Does this matter? I don't have a framework build installed, the 4-way universal build did not work for me out of the box a while ago, and installer downloads from python.org are blocked here (thanks Chinese Govt., the Great Firewall is an impressive productivity killer). So I stuck with the default Apple Python till now. For making releases, would I need the framework build? Do I need 32- and 64-bit versions of Python 2.4, 2.5 and 2.6? Cheers, Ralf diff --git a/pavement.py b/pavement.py index f6c1433..bc931ec 100644 --- a/pavement.py +++ b/pavement.py @@ -88,12 +88,13 @@ SUPERPACK_BUILD = 'build-superpack' SUPERPACK_BINDIR = os.path.join(SUPERPACK_BUILD, 'binaries') options(bootstrap=Bunch(bootstrap_dir="bootstrap"), - virtualenv=Bunch(packages_to_install=["sphinx", "numpydoc"], no_site_packages=True), + virtualenv=Bunch(packages_to_install=["sphinx", "numpydoc"], + no_site_packages=False), sphinx=Bunch(builddir="build", sourcedir="source", docroot='doc'), superpack=Bunch(builddir="build-superpack"), installers=Bunch(releasedir="release", installersdir=os.path.join("release", "installers")), - doc=Bunch(doc_root="doc", + doc=Bunch(doc_root="doc", sdir=os.path.join("doc", "source"), bdir=os.path.join("doc", "build"), bdir_latex=os.path.join("doc", "build", "latex"), @@ -106,7 +107,7 @@ options(bootstrap=Bunch(bootstrap_dir="bootstrap"), MPKG_PYTHON = { "2.5": ["/Library/Frameworks/Python.framework/Versions/2.5/bin/python"], - "2.6": ["/Library/Frameworks/Python.framework/Versions/2.6/bin/python"] + "2.6": ["python"] } SSE3_CFG = {'ATLAS': r'C:\local\lib\yop\sse3'} @@ -206,7 +207,7 @@ def bdist_superpack(options): copy_bdist("sse2") bdist_wininst_arch(pyver, 'sse3') copy_bdist("sse3") - + idirs = options.installers.installersdir pyver = options.python_version prepare_nsis_script(pyver, FULLVERSION) @@ -273,8 +274,8 @@ def bootstrap(options): options.virtualenv.script_name = os.path.join(options.bootstrap_dir, bscript) - options.virtualenv.no_site_packages = True - options.bootstrap.no_site_packages = True + options.virtualenv.no_site_packages = False + options.bootstrap.no_site_packages = False call_task('paver.virtual.bootstrap') sh('cd %s; %s %s' % (bdir, sys.executable, bscript))

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