How to pass args to the callback function in RPi.GPIO.add_event_detect()

Question

I've tried help(RPi.GPIO.add_event_detect) and checked its official wiki with no answer to that. The official example is like:
GPIO.add_event_detect(channel, GPIO.RISING, callback=my_callback, bouncetime=200)
Is there any way to pass args to my callback function (other than the pin channel) ?

---

Updates:

What I'm trying to do is to stop/resume a camera&servo task via a button. My code is like:

active = [False] 
GPIO.add_event_detect(channel, GPIO.BOTH, callback=button_callback) 
while True:
    if active[0]:  
        # camera&servo doing something which lasts seconds per loop

I want to pass the arg active to function button_callback in order to set it True/False. If I directly put GPIO.input(channel) in the while loop, I might miss the button input.
So how to pass that arg to the callback or is there any better way to achieve that?

Answer 1

You don't need to pass active to your callback function. The easiest solution for what you're doing is probably making active a global variable, so that your callback looks like this:

active = False

def button_callback(channel):
    global active
    active = GPIO.input(channel)

GPIO.add_event_detect(channel, GPIO.BOTH, callback=button_callback) 

while True:
    if active:
        # camera&servo doing something which lasts seconds per loop

You're probably going to have to deal with debouncing your switch.

---

If you really want to pursue your original plan and pass the active list to your callback function, something like this should work:

def button_callback(channel, active):
    active[0] = GPIO.input(channel)

GPIO.add_event_detect(channel, GPIO.BOTH,
                      callback=lambda channel: button_callback(channel, active))