Precise framerate calculation, scheduling and framerate limiting.

Measuring time

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

from import clock
while True:
    dt = clock.tick()
    # ... update and render ...
    print 'FPS is %f' % 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!

Limiting frame-rate

The framerate can be limited:


This causes clock to sleep during each tick in an attempt to keep the number of ticks (frames) per second below 60.

The implementation uses platform-dependent high-resolution sleep functions to achieve better accuracy with busy-waiting than would not be possible using just the time module.


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

def callback(dt):
    print '%f seconds since last callback' % dt


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

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

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


Displaying FPS

The ClockDisplay class provides a simple FPS counter. You should create an instance of ClockDisplay once during the application’s start up:

fps_display = clock.ClockDisplay()

Call draw on the ClockDisplay object for each frame:


There are several options to change the font, color and text displayed within the __init__ method.

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 limiting/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.