How to signal alarm in python 2.4 after 0.5 seconds

#! /usr/bin/env python import os import signal import threading import time class SnoozeAlarm(threading.Thread): def __init__(self, zzz): threading.Thread.__init__(self) self.setDaemon(True) self.zzz = zzz def run(self): time.sleep(self.zzz) os.kill(os.getpid(), signal.SIGALRM) def snoozealarm(i): SnoozeAlarm(i).start() def main(): snoozealarm(0.5) while True: time.sleep(0.05) print time.time() if __name__ == '__main__': main()

You have two options:

Polling time.time() or similar while the code in question runs. This is obviuosly only viable if that code is under your control.

As mentioned by pajton, you could write a C extension to call the system call setitimer(). This isn't too hard because you could simply copy the code of signal.getitimer() and signal.setitimer() from the source of later versions of Python. They are just thin wrappers around the equally named system calls.

This option is only viable if you are using CPython and you are in an environment that allows you to use custom C extensions.

Edit: Here is the code copied from signalmodule.c in Python 2.7 (Python's licence applies):

#include "Python.h"
#include <sys/time.h>

static PyObject *ItimerError;

/* auxiliary functions for setitimer/getitimer */
static void
timeval_from_double(double d, struct timeval *tv)
{
    tv->tv_sec = floor(d);
    tv->tv_usec = fmod(d, 1.0) * 1000000.0;
}

Py_LOCAL_INLINE(double)
double_from_timeval(struct timeval *tv)
{
    return tv->tv_sec + (double)(tv->tv_usec / 1000000.0);
}

static PyObject *
itimer_retval(struct itimerval *iv)
{
    PyObject *r, *v;

    r = PyTuple_New(2);
    if (r == NULL)
    return NULL;

    if(!(v = PyFloat_FromDouble(double_from_timeval(&iv->it_value)))) {
    Py_DECREF(r);
    return NULL;
    }

    PyTuple_SET_ITEM(r, 0, v);

    if(!(v = PyFloat_FromDouble(double_from_timeval(&iv->it_interval)))) {
    Py_DECREF(r);
    return NULL;
    }

    PyTuple_SET_ITEM(r, 1, v);

    return r;
}

static PyObject *
itimer_setitimer(PyObject *self, PyObject *args)
{
    double first;
    double interval = 0;
    int which;
    struct itimerval new, old;

    if(!PyArg_ParseTuple(args, "id|d:setitimer", &which, &first, &interval))
    return NULL;

    timeval_from_double(first, &new.it_value);
    timeval_from_double(interval, &new.it_interval);
    /* Let OS check "which" value */
    if (setitimer(which, &new, &old) != 0) {
    PyErr_SetFromErrno(ItimerError);
    return NULL;
    }

    return itimer_retval(&old);
}

PyDoc_STRVAR(setitimer_doc,
"setitimer(which, seconds[, interval])\n\
\n\
Sets given itimer (one of ITIMER_REAL, ITIMER_VIRTUAL\n\
or ITIMER_PROF) to fire after value seconds and after\n\
that every interval seconds.\n\
The itimer can be cleared by setting seconds to zero.\n\
\n\
Returns old values as a tuple: (delay, interval).");

static PyObject *
itimer_getitimer(PyObject *self, PyObject *args)
{
    int which;
    struct itimerval old;

    if (!PyArg_ParseTuple(args, "i:getitimer", &which))
    return NULL;

    if (getitimer(which, &old) != 0) {
    PyErr_SetFromErrno(ItimerError);
    return NULL;
    }

    return itimer_retval(&old);
}

PyDoc_STRVAR(getitimer_doc,
"getitimer(which)\n\
\n\
Returns current value of given itimer.");

static PyMethodDef itimer_methods[] = {
    {"setitimer",       itimer_setitimer, METH_VARARGS, setitimer_doc},
    {"getitimer",       itimer_getitimer, METH_VARARGS, getitimer_doc},
    {NULL,                      NULL}           /* sentinel */
};

PyMODINIT_FUNC
inititimer(void)
{
    PyObject *m, *d, *x;
    int i;
    m = Py_InitModule3("itimer", itimer_methods, 0);
    if (m == NULL)
        return;

    d = PyModule_GetDict(m);

#ifdef ITIMER_REAL
    x = PyLong_FromLong(ITIMER_REAL);
    PyDict_SetItemString(d, "ITIMER_REAL", x);
    Py_DECREF(x);
#endif
#ifdef ITIMER_VIRTUAL
    x = PyLong_FromLong(ITIMER_VIRTUAL);
    PyDict_SetItemString(d, "ITIMER_VIRTUAL", x);
    Py_DECREF(x);
#endif
#ifdef ITIMER_PROF
    x = PyLong_FromLong(ITIMER_PROF);
    PyDict_SetItemString(d, "ITIMER_PROF", x);
    Py_DECREF(x);
#endif

    ItimerError = PyErr_NewException("itimer.ItimerError",
                                     PyExc_IOError, NULL);
    if (ItimerError != NULL)
        PyDict_SetItemString(d, "ItimerError", ItimerError);
}

Save this code as itimermodule.c, compile it to a C extension using something like

gcc -I /usr/include/python2.4 -fPIC -o itimermodule.o -c itimermodule.c
gcc -shared -o itimer.so itimermodule.o -lpython2.4

Now, if you are lucky, you should be able to import this from Python using

import itimer

and call itimer.setitimer().

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