Python - Alternative to time.sleep

Question

Hello is there a alternative to time.sleep? Because I want to let my LEDs blink in the exact amount of Hz what is not able because to call time.sleep needs time too, so the blinking needs more time than expected.

#!/usr/bin/python
    import RPi.GPIO as GPIO
    import time
    from threading import Thread

    GPIO.setmode(GPIO.BOARD)
    GPIO.setup(32, GPIO.IN)

    def blink(port, hz):
        GPIO.setup(port, GPIO.OUT)
        while True:
            if GPIO.input(32) == 1:                 //lever activated?
                GPIO.output(port, GPIO.HIGH)
                time.sleep(0.5/hz)
                GPIO.output(port, GPIO.LOW)
                time.sleep(0.5/hz)
            else:
                GPIO.output(port, GPIO.LOW)
    #to make it easier to add new LED
    def start(port, hz):
        Thread(target=blink, args=(port, hz)).start()
    #to add LED insert start(GPIOport, Hz)
    start(15, 2)
    start(16, 4)
    start(18, 6)
    start(22, 12)
    start(29, 24)

Answer 1

To keep the frequency, use sleep like this:

time.sleep(desired_time - time.time())

This way the small delays will not add up.

dtm = time.time()
pulse = 0.5/Hz
while True:
    dtm += pulse
    time.sleep(dtm - time.time())
    # LED ON
    dtm += pulse
    time.sleep(dtm - time.time())
    # LED OFF

If the exact duty cycle (i.e. on/off ratio) is not a concern, you could simplify the loop:

while True:
    time.sleep(pulse)
    # LED ON
    dtm += 2*pulse
    time.sleep(dtm - time.time())
    # LED OFF

---

UPDATE, stop/resume blinking, see comments, presudocode

 pulse = 0.5/Hz
 while True:
     dtm = time.time()
     while input32 == 1:
          ... blink LEDs ...
     while not input32 == 1:
         time.sleep(0.1)