Event Detection clashing

[EvanS1]

I have a small problem.

I have two bits of code that both work as expected individually but don't work together. Suggestions as to how to fix it please.

So some context, this is running on a raspberry Pi and looking at GPIO inputs

I have a microswitch that calls some code that records the time does some other things and waits for the switch to be released updates a TKinter GUI and records that time (typically 0.5 seconds or so)
I have an optical sensor that calls another bit of code that records the time its triggered (and will eventually also update the GUI when i get that far) (this is typically happening 20 times a second I've not tested at that speed yet though)

Both of these work individually but the second doesn't work if its called while the first code is still running.

I considered firing them both into threads but you can only start a thread once.

A shortened version of the code is below (didnt think the full code was helpful as theres a lot of tkinter bits in there

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#initiallise GPIO GPIO.setmode(GPIO.BOARD) # set GPIO numbering system to Board GPIO.setup(Leftswitch,GPIO.IN) # set our sensor pin to an input GPIO.setup(Rightswitch,GPIO.IN) # set our sensor pin to an input GPIO.setup(Leftwheel,GPIO.IN)   ##Cadance def get_cadance_trig(side, sensor, c):      global Stroke_delta     if GPIO.input(sensor) == 1: ##checks GPIO value to make sure its not an end of stroke switch bounce         return     print (side)     global Stroke_start, Air_delta, count_TS, Stroke_stop     Stroke_start.append(time.time())##sets stroke start time     Air_delta = Stroke_start[-1] - Stroke_stop[-1]     print("Start stroke, air time = ", Air_delta)     count_TS = count_TS + 1     Stroke_count["text"]=count_TS     global delta_C     delta_C  = Stroke_start[-1] - Stroke_start[-sample_C]     global SPS, SPM     SPS = ((sample_C - 1) / delta_C) #calculate strokes per second (sample - 1 because we are timing gaps not strokes     SPM = SPS * 60 # convert strokes per second to per min     if Stroke_start[-3] <= (time.time()-cad_clear):# clears stroke count display if more thn 5 seconds old         SPM_count["text"]=cad_clear_dis     else:         SPM_count["text"]=int(round(SPM))     if Target == 0:         SPM_count ["fg"] = "white"     elif SPM >= Target - Targetwindow and SPM <=Target +Targetwindow:         SPM_count ["fg"] = "dark sea green"     else:         SPM_count["fg"] = "salmon"           while GPIO.input(sensor) == 0:         pass     global  Stroke_delta     Stroke_stop.append(time.time()) ##sets stooke stop for use elsewhere     Stroke_delta = Stroke_stop[-1] - Stroke_start[-1]     print("end stroke, water time = ", Stroke_delta)       def get_speed_trig(side, sensor, c):     global SpeedL, SpeedR     print (side, "wheel")     if side == "Left":         SpeedL.append(time.time())         print(SpeedL)     elif side == "Right":         SpeedR.append(time.time())         print(SpeedR[-1])     GPIO.add_event_detect(Leftswitch, GPIO.FALLING, callback=partial(get_cadance_trig, "Left", Leftswitch, ) # execute the get_cadance function when a HIGH signal is detected GPIO.add_event_detect(Rightswitch, GPIO.FALLING, callback=partial(get_cadance_trig, "right", Rightswitch, )) # execute the get_cadance function when a HIGH signal is detected GPIO.add_event_detect(Leftwheel, GPIO.FALLING, callback=partial(get_speed_trig, "Left", Leftwheel, )) # execute the get_cadance function when a HIGH signal is detected   win.mainloop()