pyglet.clock¶

Precise framerate calculation function scheduling.

Measuring time¶

The tick and get_fps functions can be used in conjunction to fulfil most games’ basic requirements:

from pyglet import clock
while True:
    dt = clock.tick()
    # ... update and render ...
    print(f"FPS is {clock.get_fps()}")

The dt value returned gives the number of seconds (as a float) since the last “tick”.

The get_fps function averages the framerate over a sliding window of approximately 1 second. (You can calculate the instantaneous framerate by taking the reciprocal of dt).

Always remember to tick the clock!

Scheduling¶

You can schedule a function to be called every time the clock is ticked:

def callback(dt):
    print(f"{dt} seconds since last callback")

clock.schedule(callback)

The schedule_interval method causes a function to be called every “n” seconds:

clock.schedule_interval(callback, .5)   # called twice a second

The schedule_once method causes a function to be called once “n” seconds in the future:

clock.schedule_once(callback, 5)        # called in 5 seconds

All of the schedule methods will pass on any additional args or keyword args you specify to the callback function:

def move(dt, velocity, sprite):
   sprite.position += dt * velocity

clock.schedule(move, velocity=5.0, sprite=alien)

You can cancel a function scheduled with any of these methods using unschedule:

clock.unschedule(move)

Using multiple clocks¶

The clock functions are all relayed to an instance of Clock which is initialised with the module. You can get this instance to use directly:

clk = clock.get_default()

You can also replace the default clock with your own:

myclk = clock.Clock() clock.set_default(myclk)

Each clock maintains its own set of scheduled functions and FPS measurement. Each clock must be “ticked” separately.

Multiple and derived clocks potentially allow you to separate “game-time” and “wall-time”, or to synchronise your clock to an audio or video stream instead of the system clock.

class Clock(time_function=<built-in function perf_counter>)¶

Class for calculating and limiting framerate.

It is also used for calling scheduled functions.

call_scheduled_functions(dt)¶

Call scheduled functions that elapsed on the last update_time.

New in version 1.2.

Parameters:	dt (float) – The elapsed time since the last update to pass to each scheduled function. This is not used to calculate which functions have elapsed.
Return type:	bool
Returns:	True if any functions were called, otherwise False.

get_fps()¶

Get the average clock update frequency of recent history.

The result is the average of a sliding window of the last “n” updates, where “n” is some number designed to cover approximately 1 second. This is not the Window redraw rate.

Return type:	float
Returns:	The measured updates per second.

get_sleep_time(sleep_idle)¶

Get the time until the next item is scheduled.

Applications can choose to continue receiving updates at the maximum framerate during idle time (when no functions are scheduled), or they can sleep through their idle time and allow the CPU to switch to other processes or run in low-power mode.

If sleep_idle is True the latter behaviour is selected, and None will be returned if there are no scheduled items.

Otherwise, if sleep_idle is False, or if any scheduled items exist, a value of 0 is returned.

Parameters:	sleep_idle (bool) – If True, the application intends to sleep through its idle time; otherwise it will continue ticking at the maximum frame rate allowed.
Return type:	float
Returns:	Time until the next scheduled event in seconds, or `None` if there is no event scheduled.

New in version 1.1.

schedule(func, *args, **kwargs)¶

Schedule a function to be called every frame.

The function should have a prototype that includes dt as the first argument, which gives the elapsed time, in seconds, since the last clock tick. Any additional arguments given to this function are passed on to the callback:

def callback(dt, *args, **kwargs):
    pass

Parameters:	func (callable) – The function to call each frame.

schedule_interval(func, interval, *args, **kwargs)¶

Schedule a function to be called every interval seconds.

Specifying an interval of 0 prevents the function from being called again (see schedule to call a function as often as possible).

The callback function prototype is the same as for schedule.

Parameters:	func (callable) – The function to call when the timer lapses. interval (float) – The number of seconds to wait between each call.

schedule_interval_soft(func, interval, *args, **kwargs)¶

Schedule a function to be called every interval seconds.

This method is similar to schedule_interval, except that the clock will move the interval out of phase with other scheduled functions so as to distribute CPU more load evenly over time.

This is useful for functions that need to be called regularly, but not relative to the initial start time. pyglet.media does this for scheduling audio buffer updates, which need to occur regularly – if all audio updates are scheduled at the same time (for example, mixing several tracks of a music score, or playing multiple videos back simultaneously), the resulting load on the CPU is excessive for those intervals but idle outside. Using the soft interval scheduling, the load is more evenly distributed.

Soft interval scheduling can also be used as an easy way to schedule graphics animations out of phase; for example, multiple flags waving in the wind.

New in version 1.1.

Parameters:	func (callable) – The function to call when the timer lapses. interval (float) – The number of seconds to wait between each call.

schedule_once(func, delay, *args, **kwargs)¶

Schedule a function to be called once after delay seconds.

The callback function prototype is the same as for schedule.

Parameters:	func (callable) – The function to call when the timer lapses. delay (float) – The number of seconds to wait before the timer lapses.

static sleep(microseconds)¶

tick(poll=False)¶

Signify that one frame has passed.

This will call any scheduled functions that have elapsed.

Parameters:	poll (bool) – If True, the function will call any scheduled functions but will not sleep or busy-wait for any reason. Recommended for advanced applications managing their own sleep timers only. Since pyglet 1.1.
Return type:	float
Returns:	The number of seconds since the last “tick”, or 0 if this was the first frame.

unschedule(func)¶

Remove a function from the schedule.

If the function appears in the schedule more than once, all occurrences are removed. If the function was not scheduled, no error is raised.

Parameters:	func (callable) – The function to remove from the schedule.

update_time()¶

Get the elapsed time since the last call to update_time.

This updates the clock’s internal measure of time and returns the difference since the last update (or since the clock was created).

New in version 1.2.

Return type:	float
Returns:	The number of seconds since the last update_time, or 0 if this was the first time it was called.

MIN_SLEEP = 0.005¶: On Windows, MIN_SLEEP is larger because the default timer resolution is set by default to 15 .6 ms.

SLEEP_UNDERSHOOT = 0.004¶: The amount of time in seconds this clock subtracts from sleep values to compensate for lazy operating systems.

get_default()¶

Get the pyglet default Clock.

Return the Clock instance that is used by all module-level clock functions.

Return type:	Clock
Returns:	The default clock.

get_fps()¶

Get the average clock update frequency.

The result is the sliding average of the last “n” updates, where “n” is some number designed to cover approximately 1 second. This is the internal clock update rate, not the Window redraw rate. Platform events, such as moving the mouse rapidly, will cause the clock to refresh more often.

Return type:	float
Returns:	The measured updates per second.

get_sleep_time(sleep_idle)¶

Get the time until the next item is scheduled on the default clock.

See Clock.get_sleep_time for details.

Parameters:	sleep_idle (bool) – If True, the application intends to sleep through its idle time; otherwise it will continue ticking at the maximum frame rate allowed.
Return type:	float
Returns:	Time until the next scheduled event in seconds, or `None` if there is no event scheduled.

New in version 1.1.

schedule(func, *args, **kwargs)¶

Schedule ‘func’ to be called every frame on the default clock.

The arguments passed to func are dt, followed by any *args and **kwargs given here.

Parameters:	func (callable) – The function to call each frame.

schedule_interval(func, interval, *args, **kwargs)¶

Schedule func on the default clock every interval seconds.

The arguments passed to func are dt (time since last function call), followed by any *args and **kwargs given here.

Parameters:	func (callable) – The function to call when the timer lapses. interval (float) – The number of seconds to wait between each call.

schedule_interval_soft(func, interval, *args, **kwargs)¶

Schedule func on the default clock every interval seconds.

The clock will move the interval out of phase with other scheduled functions so as to distribute CPU more load evenly over time.

The arguments passed to func are dt (time since last function call), followed by any *args and **kwargs given here.

See:	Clock.schedule_interval_soft

New in version 1.1.

Parameters:	func (callable) – The function to call when the timer lapses. interval (float) – The number of seconds to wait between each call.

schedule_once(func, delay, *args, **kwargs)¶

Schedule func to be called once after delay seconds.

This function uses the default clock. delay can be a float. The arguments passed to func are dt (time since last function call), followed by any *args and **kwargs given here.

If no default clock is set, the func is queued and will be scheduled on the default clock as soon as it is created.

Parameters:	func (callable) – The function to call when the timer lapses. delay (float) – The number of seconds to wait before the timer lapses.

set_default(default)¶

Set the default clock to use for all module-level functions.

By default an instance of Clock is used.

Parameters:	default (Clock) – The default clock to use.

tick(poll=False)¶

Signify that one frame has passed on the default clock.

This will call any scheduled functions that have elapsed.

Parameters:	poll (bool) – If True, the function will call any scheduled functions but will not sleep or busy-wait for any reason. Recommended for advanced applications managing their own sleep timers only. Since pyglet 1.1.
Return type:	float
Returns:	The number of seconds since the last “tick”, or 0 if this was the first frame.

unschedule(func)¶

Remove func from the default clock’s schedule.

No error is raised if the func was never scheduled.

Parameters:	func (callable) – The function to remove from the schedule.