Latest recipes tagged "signal"

Simple signal library, similar to PyQT signals (Python)

2017-04-01T21:11:50-07:00

Python recipe 580764 by Miguel Martínez López (event, pubsub, signal). Revision 11.

Simple signal library similar to PyQT signals. Signals helps to decouple code in GUI applications. This code could be used in Tkinter applications for example.

Inspired and based in these other modules:

https://github.com/shaunduncan/smokesignal

https://github.com/dgovil/PySignal

https://github.com/jek/blinker

Register exit function (Python)

2016-05-31T00:42:47-07:00

Python recipe 580672 by Giampaolo Rodolà (exit, python, signal). Revision 3.

This is a function / decorator which registers a function which will be executed on "normal" interpreter exit or in case one of the signals is received by this process (differently from atexit.register()). Also, it makes sure to execute any other function which was previously registered via signal.signal(). If any, it will be executed after our own fun. The full blogpost explaining why you should use this instead of atexit module is here: http://grodola.blogspot.com/2016/02/how-to-always-execute-exit-functions-in-py.html

Discrete Fourier Transform (Python)

2014-12-27T21:43:53-08:00

Python recipe 578994 by FB36 (math, mathematics, signal, signal_processing).

Discrete Fourier Transform and Inverse Discrete Fourier Transform

To test, it creates an input signal using a Sine wave that has known frequency, amplitude, phase. Later it calculates DFT of the input signal and finds its frequency, amplitude, phase to compare.

Platform Independent White Noise Generator... (Python)

2012-11-25T10:10:45-08:00

Python recipe 578350 by Barry Walker (apple, audio, demo, generator, linux, macbook_pro, noise, program, pyaudio, signal, sound, source, windows).

This code is a derivative of the Pure Sinewave Generator and produces a continuous noise out of the speakers or headphone sockets.

It is for the hobbyist to be able to generate a pseudo-random noise signal for testing with.

It is issued as Public Domian and you may do with it as you please.

It is very easy to convert to Python 3.x.x but as OSX only has 2.7.x and lower ATM then these are what are used...

An installation of pyaudio IS needed for this to work; see the code for more information.

It is near platform independent but sadly the AMIGA is not included, but hey, I have already shown how generate sound for Classic AMIGAs.

Enjoy finding simple solutions to often very difficult problems...

Bazza, G0LCU...

Platform Independent 1KHz Pure Audio Sinewave Generator... (Python)

2012-10-23T12:53:37-07:00

Python recipe 578301 by Barry Walker (apple, audio, demo, generator, linux, macbook_pro, program, pyaudio, signal, sinewave, sound, source, windows). Revision 2.

IKHz_SW_OSX.py

A mono _pure_ sinewave generator using standard text mode Python 2.6.7 to at least 2.7.3.

This DEMO kids level 1KHz generator is mainly for a MacBook Pro, (13 inch in my case), OSX 10.7.5 and above. See below...

It is another simple piece of testgear for the young amateur electronics enthusiast and uses pyaudio fully installed for it to work.

PyAudio can be obtained from here:- http://people.csail.mit.edu/hubert/pyaudio/

This was primarily for a MacBook Pro, but works on at least 2 Linux flavours and Windows Vista 32 bit...

The sinewave generated is near excellent...

Enjoy finding simple solutions to often very difficult problems... Bazza, G0LCU...

Handle exit context manager (Python)

2014-08-01T08:28:07-07:00

Python recipe 577997 by Giampaolo Rodolà (atexit, contextlib, contextmanager, exit, python, python3, shutdown, sigint, signal, sigterm). Revision 23.

A context manager which properly handles SIGTERM (SystemExit) and SIGINT (KeyboardInterrupt) signals, registering a function which is always guaranteed to be called on interpreter exit. Also, it makes sure to execute previously registered functions as well (if any).

Yet Another Python Generator... (Python)

2011-12-19T08:14:55-08:00

Python recipe 577990 by Barry Walker (audio, demo, generator, linux, signal, sound, source, sweep).

Aha, but not what big guns were expecting...

LF Audio Sweep Generator.

Another kids level project to do for yourselves...

This is a Python DEMO to show the power of the sound card using Linux to generate an Audio Sweep Signal from 4KHz down to 100Hz and back again.

Written in such a way that anyone can understand how it works... This is for Linux and Python 2.x.x. Read the code for much more information, and...... A Python 3.x.x version is here:-

http://www.linuxformat.com/forums/viewtopic.php?t=14411

Enjoy finding simple solutions to often VERY difficult problems...

Bazza, G0LCU...

Improved Signals/Slots implementation in Python (Python)

2011-12-12T22:47:25-08:00

Python recipe 577980 by Christopher S. Case (events, qt4, signal, slot).

I've modified the excellent recipe 576477 to allow for non method functions as well as method functions. This implementation also uses a WeakKeyDictionary instead of a WeakValueDictionary for reasons of code simplification/style.

POSIX Semaphore (FreeBSD) (Python)

2011-04-14T17:54:16-07:00

Python recipe 577655 by David Naylor (ctypes, freebsd, semaphores, signal, threads).

POSIX Semaphore bindings for FreeBSD.

Simple White Noise Generator Using Standard Python In Linux. (Python)

2011-03-10T18:03:55-08:00

Python recipe 577604 by Barry Walker (audio, demo, generator, linux, noise, program, signal, sound, source).

Simple White Noise Generator Using Standard Python In Linux - noise.py

This code is a stand alone program to generate a signal, at the earphone sockets, of white noise.

It needs /dev/dsp to work; if you haven't got it then install oss-compat from your distro's repository. (NOTE:- /dev/audio could also be used but I decided to use /dev/dsp to show that this was within easy reach of standard Python too.)

Ensure the audio system is NOT in use for this to work and all the levels are set up for your normal requirements. In my case root level WAS NOT required but that does not mean that root level IS NOT required - so be aware.

All that is required to make this a piece of audio test equipment is a cable plugged into to the earphone socket. The output level is fully controllable inside the code and the noise is generated in about 10 second bursts

Assuming it is copied into the module(s) drawer just type:-

>>> import noise[RETURN/ENTER]

And away you go...

This is Public Domain and you may do with it as you like.

Read the program for more information. (There will be more to come in the future... :)

Enjoy finding simple solutions to often very difficult problems... ;o)

73...

Bazza, G0LCU...

Team AMIGA...

Queue for managing multiple SIGALRM alarms concurrently (Python)

2012-12-06T18:58:11-08:00

Python recipe 577600 by Glenn Eychaner (alarm, queue, signal). Revision 3.

In asynchronous code, signal.alarm() is extremely useful for setting and handling timeouts and other timed and periodic tasks. It has a major limitation, however, that only one alarm function and alarm time can be set at a time; setting a new alarm disables the previous alarm. This package uses a heapq to maintain a queue of alarm events, allowing multiple alarm functions and alarm times to be set concurrently.

Simple 1KHz Audio Function Generator Using Standard Python In Linux... (Python)

2011-03-01T19:37:16-08:00

Python recipe 577592 by Barry Walker (audio, demo, function, generator, linux, program, signal, sound, source).

Simple 1KHz Audio Function Generator Using Standard Python In Linux - afg.py

This code is a stand alone program to generate a signal, at the earphone sockets, of 1KHz. It is a basic audio signal generator and can be used as a starter test signal source for amateur electronics enthusiasts testgear suite(s).

It needs /dev/audio to work; if you haven't got it then install oss-compat from your distro's repository.

Ensure the audio system is NOT in use for this to work.

Sine, Square, Triangle, Sawtooth+, Sawtooth-, Pulse+ and Pulse- signals are generated in 10 second bursts. The waveforms generated are unfiltered and therefore not "pure", but hey, an audio function generator signal source, for free, without external hardware, AND, using standard Python, what more do you want... :) An oscilloscope will show the waveforms generated at the earphone socket.

Noise is not included but that is SO easy that I left it out FTTB. (This will be a future upload. ;o)

All that is required to make this a piece of audio test equipment is a cable plugged into to the earphone socket.

Assuming it is copied into the module(s) drawer just type:-

>>> import afg[RETURN/ENTER]

And away you go...

This is Public Domain and you may do with it as you like.

Read the program for more information. (There will be more to come in the future... :)

sigaction on SIGCHLD (C)

2009-05-25T23:54:57-07:00

C recipe 576776 by J Y (signal). Revision 2.

sigaction

pending/blocking a signal (C)

2009-05-25T22:42:30-07:00

C recipe 576775 by J Y (signal).

http://www-h.eng.cam.ac.uk/help/tpl/unix/signals.html

do you want certain signals to be ignored or blocked? The sigaction(), sigprocmask(), siginterrupt(), and sigsuspend() functions control the manipulation of the signal mask, which defines the set of signals currently blocked. The manual pages give details. The following code shows how the response to signals can be delayed.

Debugging a running python process by interrupting and providing an interactive prompt (Python)

2008-09-25T11:23:29-07:00

Python recipe 576515 by Brian McErlean (debug, interactive, remote, signal). Revision 2.

This provides code to allow any python program which uses it to be interrupted at the current point, and communicated with via a normal python interactive console. This allows the locals, globals and associated program state to be investigated, as well as calling arbitrary functions and classes.

To use, a process should import the module, and call listen() at any point during startup. To interrupt this process, the script can be run directly, giving the process Id of the process to debug as the parameter.

Yet another signal/slot implementation in Python (Python)

2008-09-01T23:21:28-07:00

Python recipe 576477 by Thiago Marcos P. Santos (observer, publish, signal, slot, subscribe, weakref).

This code snippet was based on the nice recipe 439356 made by Patrick Chasco. My implementation supports only class methods callbacks. I'm keeping the idea of use weakrefs to avoid the interpreter keep the object allocated because the signal is registered (i.e. the signal object holds a reference to callback method). IMO the usage of WeakValueDictionary made the code smaller and clear and also are maintenance-free (when the object is collect by the garbage collector the signal is automatically unregistered).