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• What's the fastest way to approximate the period of data using Octave?

  - by John

  I have a set of data that is periodic (but not sinusoidal). I have a set of time values in one vector and a set of amplitudes in a second vector. I'd like to quickly approximate the period of the function. Any suggestions? Specifically, here's my current code. I'd like to approximate the period of the vector x(:,2) against the vector t. Ultimately, I'd like to do this for lots of initial conditions and calculate the period of each and plot the result. function xdot = f (x,t) xdot(1) =x(2); xdot(2) =-sin(x(1)); endfunction x0=[1;1.75]; #eventually, I'd like to try lots of values for x0(2) t = linspace (0, 50, 200); x = lsode ("f", x0, t) plot(x(:,1),x(:,2)); Thank you! John

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• os.path.getmtime() doesn't return fraction of a second

  - by haridsv

  I compile python 2.6.4 for centos 5.3 and find this issue that os.path.getmtime() or os.stat().m_time doesn't have the fraction part. As per docs, if os.stat_float_times() True, then it should return float value. In my case, I do see it as float, but no fraction part (it is 0). In [3]: os.path.getmtime('/tmp') Out[3]: 1268339116.0 In [4]: os.stat('/tmp') Out[4]: posix.stat_result(st_mode=17407, st_ino=508897L, st_dev=29952L, st_nlink=7, st_uid=0, st_gid=0, st_size=4096L, st_atime=1268101696, st_mtime=1268339116, st_ctime=1268339116) In [5]: os.stat_float_times() True In [6]: os.stat('/tmp').st_mtime Out[6]: 1268339116.0 It is also strange that the stat() output seems like an int. On windows, I do see a fraction part with the same python version. I am running centos on top of colinux, could that be playing a role, or is it some python build issue? I couldn't find any hits for generic colinux issue. May be it is how colinux configures the filesystem? What would I need to check in that case?

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• what is a fast way to output h5py dataset to text?

  - by user362761

  I am using the h5py python package to read files in HDF5 format. (e.g. somefile.h5) I would like to write the contents of a dataset to a text file. For example, I would like to create a text file with the following contents: 1,20,31,75,142,324,78,12,3,90,8,21,1 I am able to access the dataset in python using this code: import h5py f = h5py.File('/Users/Me/Desktop/thefile.h5', 'r') group = f['/level1/level2/level3'] dset = group['dsetname'] My naive approach is too slow, because my dataset has over 20000 entries: # write all values to file for index in range(len(dset)): # do not add comma after last value if index == len(dset)-1: txtfile.write(repr(dset[index])) else: txtfile.write(repr(dset[index])+',') txtfile.close() return None Is there a faster way to write this to a file? Perhaps I could convert the dataset into a NumPy array or even a Python list, and then use some file-writing tool? (I could experiment with concatenating the values into a larger string before writing to file, but I'm hoping there's something entirely more elegant)

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• Convolving two signals

  - by John Elway

  Calculate the convolution of the following signals (your answer will be in the form of an equation): h[n] = delta[n-1] + delta[n+1], x[n] = delta[n-a] + delta[n+b] I'm lost as to what I do with h and x. Do I simply multiply them? h[n]*x[n]? I programmed convolution with several types of blurs and edge detectors, but I don't see how to translate that knowledge to this problem. please help!

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• os.fork() sem_wait: Permission denied

  - by Roger

  I am trying to compile python 2.5 on AIX 6.1, and the following occurs: Python 2.6.5 (r265:79063, Jun 3 2010, 11:43:45) [GCC 4.2.0] on aix6 Type "help", "copyright", "credits" or "license" for more information. >>> import os >>> os.fork() 0 sem_wait: Permission denied 741398 I have found this bug, which sounds similar: http://bugs.python.org/issue1234 which suggests setting HAVE_BROKEN_POSIX_SEMAPHORES I have tried this by modifying the configure script, and I can see it being set, but that does not help.. Any ideas ??

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• Which Language to target on Ubuntu?

  - by WeNeedAnswers

  I'm a c# programmer by trade and looking to move my wares over to Ubuntu as a business concern. I have some experience of Python and like it a lot. My question is, as a developer which would be the best language to use when targeting ubuntu Mono c# or python as a commercial concern. please note that I am not interested in the technical aspects but strictly the commercials of where Ubuntu is heading, I see that there is a lot of work done within using Python and thinking that maybe with the whole Mono issue of who "might" purchase them.

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• Help to run it in the background

  - by AlexPolo

  Here's a simple python daemon I can't manage to run as a background process: #!/usr/bin/env python import socket host = '' port = 843 backlog = 5 size = 1024 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind((host,port)) s.listen(backlog) while 1: client, address = s.accept() data = client.recv(size) if data == '<policy-file-request/>\0': client.send('<?xml version="1.0"?><cross-domain-policy><allow-access-from domain="*" to-ports="*"/></cross-domain-policy>') client.close() It's a socket policy file server (you may have heard of the restiction Adope put on socket connection - http://www.adobe.com/devnet/flashplayer/articles/socket_policy_files.html); that works well when gets run like an "ordinary" process - "python that_server.py", - but I get problem to run it in the background. Running like so: "that_server.py &", - does not work.

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• Google Search API - Only returning 4 results

  - by user353829

  After much experimenting and googling, the following Python code successfully calls Google's Search APi - but only returns 4 results: after reading the Google Search API docs, I thought the 'start=' would return additional results: but this not happen. Can anyone give pointers? Thanks. Python code: /usr/bin/python import urllib import simplejson query = urllib.urlencode({'q' : 'site:example.com'}) url = 'http://ajax.googleapis.com/ajax/services/search/web?v=1.0&%s&start=50' \ % (query) search_results = urllib.urlopen(url) json = simplejson.loads(search_results.read()) results = json['responseData']['results'] for i in results: print i['title'] + ": " + i['url']

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• BlackBerry Technical Specification

  - by Sam

  I'm having trouble locating BlackBerry techical specifications and their website is a mess. They also don't have a number that I can use to easily contact them. This isn't exactly a coding question, but what does the BlackBerry audio API look like, and where can I get technical specifications on audio? Specifically, I'm trying to find out more information on Audio-In, specifically, through the Mic-In on the 3.5 mm jack. Unfortunately, before I can proceed, I need to know such things like sampling rate, data width, etc. Direction to the right resource or if you know off of the top of your head is appreciated.

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• Does enlarging images make them easier to analyze programmatically?

  - by indoman

  Can you enlarge a feature so that rather than take up a certain number of pixels it actually takes up one or two times that many to make it easier to analyze? Would there be a way to generalize that in MATLAB?

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• Why is object destructor not called when script terminates ?

  - by planetp

  I have a test script like this: package Test; sub new { bless {} } sub DESTROY { print "in DESTROY\n" } package main; my $t = new Test; sleep 10; The destructor is called after sleep returns (and before the program terminates). But it's not called if the script is terminated with Ctrl-C. Is it possible to have the destructor called in this case also?

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• Automatically create valid links

  - by Marcos Placona

  Hi, I'm new to python, so please bare with me :) I was wondering if there's any built-in way in python to append variables to URL's regardless of it's structure. I would like to have a URL variable (test=1) added to an URL which could have any of the following structures http://www.aaa.com (would simply add "/?test=1") to the end http://www.aaa.com/home (like the one above, would simply add "/?test=1") to the end http://www.aaa.com/?location=home (would figure out there's already a ? being used, and would add &test=1 to the end) http://www.aaa.com/?location=home&page=1 (like the one above, would figure out there's already a ? being used, and would add &test=1 to the end) I'd be happy to write domething to do it myself, but if python can already do it somehow, I'd me more than happy to use any built-in functionality that would save me some time ;-) Thanks in advance

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• How does exactly Qt works?

  - by Somebody still uses you MS-DOS

  I have seen that you can write your application in Qt, and it can be run in different operating systems. And - correct me if I'm wrong - you don't need to have Qt already installed in all of these platforms. How exactly this approach works? Does Qt compiles to the desired platform, does it bundle some "dlls" (libs), how does it do it? Is different from programming a Java application for the sake of cross-platform? If you use Python to write a Qt application with Python bindings, does the final user needs to have Python installed?

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• pyschool is wrong ?

  - by geekkid

  I'm currently learning python and trying to do exercises at pyschools (if anyone knows what it is). Anyway, i have an exercise that asks me to do the following : Write a function percent(value, total) that takes in two numbers as arguments, and returns the percentage value as an integer. Here's my code: def percent(value, total): percent = value / total * 100 return int(percent) It works great in my Python Idle and it gives all the correct answers. however, when i run it in the pyschools website, it says that , for example , when the function is called with parameters 46 and 90 , the function returns 0. However, in my python idle , it correctly returns 51. What might be the problem ? Thank you very much for your help!

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• How to add a slot to my main window in Qt builder?

  - by George Edison

  I am using Qt Builder to create a simple window. I used the menu editor to add a menu. Now, I figured out how to connect one of the menu items to the close() method of the main window. My problem is how to add a slot to the main window. Here is what I have: private slots: void OnAbout(); However, I can't get this method to show up in the 'Signals and Slots Editor'. How can I get it to show up?

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• "Voice trigger" detection

  - by sehugg

  I have a voice application that would be much-improved if there was the ability to use a "trigger word" to start recording audio. I don't need a full speech-text engine, just the ability to reliably/efficiently detect the trigger word. I am wondering if there are any specialized speech engines that support this specific use case, or any libraries/methods to developing such a single-purpose detection engine. Ideally I'd like it to work in noisy environments, but it can be trained for a single user's voice. Pointers to research papers / topics would also be appreciated so I know what to ask for.

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• Weird behaviour with optparse and bash tab completion

  - by PulpFiction

  Hi I am building a script for users new to Linux, so please understand why I am asking this :) My script runs like this: python script.py -f filename.txt I am using the optparse module for this. However, I noticed the following when doing tab completion. The tab completion works when I do: python script.py <tab completion> # Tab completion works normally as expected But it does not work when I do it like this: python script.py -f <tab completion> # No type of tab completion works here. I really don't want my users typing the name of the input file. Tab completion is a must. How can I get it working or what am I doing wrong here?

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• Compare two audio files of beat/tempo and rating in iphone

  - by Senthil Kumar

  Hello, I want to develop iPhone application should have the ability to count the number of phrases that are received when user sing on mic. This application should also have the ability to decipher whether the users phrases are in or out of cadence with a preset beat.When user sing on mic Instrumental music only play. So I have to merge the User Recorded voice with Instrumental music this is one Audio file.Already i have on original Song file.I have to compare both and give the Rating to users. [Note: Instrumental music is without vocal of Original Song file] Can you please help me?. Thanks Vadivelu

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• How do I control widgets added later with gtk in c?

  - by Runner

  func1(); func2(); ... In func1 there is a button widget,and in func2 a textview widget. I want to operate textview when I click on button widget. But at the time I define the callback,textview is not available yet. How can I work around this?

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• Finding center of fingerprints.

  - by an_ant

  If we suppose that every fingerprint is made of concentric curves (ellipses or circles) - and I'm aware of the fact that not every fingerprint is - how can I find center of those concentric curves? Let's take this "ideal" fingerprint and try to find out its center ... My approaches were to try: Find the spectrum through columns/rows of the image and try to find columns/rows that maximize particular band of the spectrum. I thought that column going through the center would have most regular pattern of changing amplitudes - therefore, most recognizible harmonic. My second approach was to try to count the changes of black-and-white also through the columns and rows, and to maximize that amount among rows and columns also. While these methods work to the some extant, with some additional filtering, they fail, when fingerprint is "not ideal as this one is". Can you think of any different approach? Are there standard ways to do it?

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• Why is the value of __name__ changing after assignment to sys.modules[__name__]?

  - by martineau

  While trying to do something similar to what's in the ActiveState recipe titled Constants in Python by Alex Martelli, I ran into an unexpected side-effect that assigning a class instance to an entry in sys.modules apparently has in Python 2.7 -- namely that doing so apparent changes the value of __name__ to None as illustrated in the following code fragment: class _test(object): pass import sys print '__name__: %r' % __name__ # __name__: '__main__' sys.modules[__name__] = _test() print '__name__: %r' % __name__ # __name__: None if __name__ == '__main__': # never executes... import test print "done" I'd like to understand why this is happening. I don't believe it was that way in Python 2.6 and earlier versions since I have some older code where apparently the if __name__ == '__main__': conditional worked as expected following the assignment (but no longer does). FWIW, I also noticed that the name _class is getting rebound from a class object to None, too, after the assignment. Also seems odd to me that they're being rebound to 'None' rather than disappearing altogether... Update: I'd like to add that any workarounds for achieving the effect of if __name__ == '__main__':, given what happens would be greatly appreciated. TIA!

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• Why does py2exe remove `help` and `license`?

  - by cool-RR

  I packaged my Python app with py2exe. My app is a wxPython GUI, in which there is an interactive Python shell. I noticed that I can't do help(whatever) in the shell. I investigated a bit and discovered that after the py2exe process, 3 items were missing from __builtin__. These are help, license, and another one I haven't discovered. Why is this happening and how can I stop it? I want the users of my program to be able to use the help function of Python.

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• How to manually close connection in BaseHTTPServer?

  - by user1657188

  I have a script that sends a request to an HTTP server. HTTP server script (snippet): ... class MyHandler(BaseHTTPServer.BaseHTTPRequestHandler): def do_GET(sa): pdict = cgi.parse_header(sa.headers.getheader('referer')) q = pdict[0] q = urllib.unquote(q) if q == "enternetixplorer" # basically just ignore this, doesn't have to do with the question sa.wfile.write("blah blah blah") # now restart server httpd.server_close() python = sys.executable os.execl(python, python, * sys.argv) ... The "blah blah blah" is sent back, but the connection does not seem to close, and my script is waiting forever until I abort the server. (My thought is BaseHTTPServer automatically closes connection when the last part in "do_GET()" is computed, but I prevent this by restarting the script.) If I'm right, how do I close the connection? If not, what else might be the problem? Edit: The server script HAS to restart the entire program.

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• Inversion of an image

  - by carlsbad

  How do you invert an image (reversing grayscale) in Matlab?

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• Comapring pitches with digital audio

  - by user2250569

  I work on application which will compare musical notes with digital audio. My first idea was analyzes wav file (or sound in real-time) with some polyphonic pitch algorithms and gets notes and chords from this file and subsequently compared with notes in dataset. I went through a lot of pages and it seems to be a lot of hard work because existing implementations and algorithms are mainly/only focus on monophonic sound. Now, I got the idea to do this in the opposite way. In dataset I have for example note: A4 or better example chord: A4 B4 H4. And my idea is make some wave (or whatever I don't know what) from this note or chord and then compared with piece of digital audio. Is this good idea? Is it better/harder solution? If yes can you recommend me how to do it?

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