make a program wait for a few seconds...

[mahela007]

How can I make a program wait for a few seconds before proceeding? An example of where this would come in handy is when the program allows the user 5 seconds before it proceeds with some default option... can I do this using python?

[slate]

Try:
time.sleep

http://www.daniweb.com/forums/thread63297.html#

[snippsat]

>>> import time
>>> dir(time)
['__doc__',
 '__name__',
 '__package__',
 'accept2dyear',
 'altzone',
 'asctime',
 'clock',
 'ctime',
 'daylight',
 'gmtime',
 'localtime',
 'mktime',
 'sleep',
 'strftime',
 'strptime',
 'struct_time',
 'time',
 'timezone',
 'tzname']
>>> help(time.sleep)
Help on built-in function sleep in module time:

sleep(...)
    sleep(seconds)
    
    Delay execution for a given number of seconds.  The argument may be
    a floating point number for subsecond precision.

>>>

[mahela007]

Thanks... that's what I needed. However, I'd like to know HOW a timer is created in python.

[Gribouillis]

Thanks... that's what I needed. However, I'd like to know HOW a timer is created in python.

Apart from the sleep function, there is a Timer class in the threading module and there are timers in gui modules like tkinter and wxpython. Other ways to wait are the threading.Condition.wait() function, socket reading with a timeout and functions like select.select which wait for I/O with an optional timeout.
Your choice depends on what you want to do exactly.

[vegaseat]

You can also keep a program busy with a for loop, but the exact delay will depend on your computer's capabilities.

[mahela007]

Apart from the sleep function, there is a Timer class in the threading module and there are timers in gui modules like tkinter and wxpython. Other ways to wait are the threading.Condition.wait() function, socket reading with a timeout and functions like select.select which wait for I/O with an optional timeout.
Your choice depends on what you want to do exactly.

What I meant was 'how does python keep track of the passing seconds'? Does it count the clock pulses or something like that?

[vegaseat]

As far as I understand, module time and most timers use the hardware timer (internal clock chip). Using a float representing UTC time in seconds since the epoch created by the chip. The epoch on most of those chips is 1/1/1970 00:00:00

You can see seconds since epoch with this little Python program ...

import time

print(time.time())

This value is updated 18.2 times per second.

[Gribouillis]

Looking into pyton 2.6 source code (timemodule.c) we find this implementation of sleep

/* Implement floatsleep() for various platforms.
   When interrupted (or when another error occurs), return -1 and
   set an exception; else return 0. */

static int
floatsleep(double secs)
{
/* XXX Should test for MS_WINDOWS first! */
#if defined(HAVE_SELECT) && !defined(__BEOS__) && !defined(__EMX__)
	struct timeval t;
	double frac;
	frac = fmod(secs, 1.0);
	secs = floor(secs);
	t.tv_sec = (long)secs;
	t.tv_usec = (long)(frac*1000000.0);
	Py_BEGIN_ALLOW_THREADS
	if (select(0, (fd_set *)0, (fd_set *)0, (fd_set *)0, &t) != 0) {
#ifdef EINTR
		if (errno != EINTR) {
#else
		if (1) {
#endif
			Py_BLOCK_THREADS
			PyErr_SetFromErrno(PyExc_IOError);
			return -1;
		}
	}
	Py_END_ALLOW_THREADS
#elif defined(__WATCOMC__) && !defined(__QNX__)
	/* XXX Can't interrupt this sleep */
	Py_BEGIN_ALLOW_THREADS
	delay((int)(secs * 1000 + 0.5));  /* delay() uses milliseconds */
	Py_END_ALLOW_THREADS
#elif defined(MS_WINDOWS)
	{
		double millisecs = secs * 1000.0;
		unsigned long ul_millis;

		if (millisecs > (double)ULONG_MAX) {
			PyErr_SetString(PyExc_OverflowError,
					"sleep length is too large");
			return -1;
		}
		Py_BEGIN_ALLOW_THREADS
		/* Allow sleep(0) to maintain win32 semantics, and as decreed
		 * by Guido, only the main thread can be interrupted.
		 */
		ul_millis = (unsigned long)millisecs;
		if (ul_millis == 0 ||
		    main_thread != PyThread_get_thread_ident())
			Sleep(ul_millis);
		else {
			DWORD rc;
			ResetEvent(hInterruptEvent);
			rc = WaitForSingleObject(hInterruptEvent, ul_millis);
			if (rc == WAIT_OBJECT_0) {
				/* Yield to make sure real Python signal
				 * handler called.
				 */
				Sleep(1);
				Py_BLOCK_THREADS
				errno = EINTR;
				PyErr_SetFromErrno(PyExc_IOError);
				return -1;
			}
		}
		Py_END_ALLOW_THREADS
	}
#elif defined(PYOS_OS2)
	/* This Sleep *IS* Interruptable by Exceptions */
	Py_BEGIN_ALLOW_THREADS
	if (DosSleep(secs * 1000) != NO_ERROR) {
		Py_BLOCK_THREADS
		PyErr_SetFromErrno(PyExc_IOError);
		return -1;
	}
	Py_END_ALLOW_THREADS
#elif defined(__BEOS__)
	/* This sleep *CAN BE* interrupted. */
	{
		if( secs <= 0.0 ) {
			return;
		}

		Py_BEGIN_ALLOW_THREADS
		/* BeOS snooze() is in microseconds... */
		if( snooze( (bigtime_t)( secs * 1000.0 * 1000.0 ) ) == B_INTERRUPTED ) {
			Py_BLOCK_THREADS
			PyErr_SetFromErrno( PyExc_IOError );
			return -1;
		}
		Py_END_ALLOW_THREADS
	}
#elif defined(RISCOS)
	if (secs <= 0.0)
		return 0;
	Py_BEGIN_ALLOW_THREADS
	/* This sleep *CAN BE* interrupted. */
	if ( riscos_sleep(secs) )
		return -1;
	Py_END_ALLOW_THREADS
#elif defined(PLAN9)
	{
		double millisecs = secs * 1000.0;
		if (millisecs > (double)LONG_MAX) {
			PyErr_SetString(PyExc_OverflowError, "sleep length is too large");
			return -1;
		}
		/* This sleep *CAN BE* interrupted. */
		Py_BEGIN_ALLOW_THREADS
		if(sleep((long)millisecs) < 0){
			Py_BLOCK_THREADS
			PyErr_SetFromErrno(PyExc_IOError);
			return -1;
		}
		Py_END_ALLOW_THREADS
	}
#else
	/* XXX Can't interrupt this sleep */
	Py_BEGIN_ALLOW_THREADS
	sleep((int)secs);
	Py_END_ALLOW_THREADS
#endif

	return 0;
}

The code is OS dependent. For linux, you see that the sleep is implemented by calling select(0,0,0,0, &t) , so your question is now to find the implementation of the C function select. On other OSes, there seem to be a system Sleep or DosSleep function, and you should look for their implementations with the help of our good friend GOOGLE.

[mahela007]

Oh dear.. I think I'll leave it at that... ;-) Thanks for your help.