This may be simpler than I think but I'd like to create timer that, upon reaching a limit (say 15 mins), some code is executed.
Meanwhile every second, I'd like to test for a condition. If the condition is met, then the timer is reset and the process begins again, otherwise the countdown continues.
If the condition is met after the countdown has reached the end, some code is executed and the timer starts counting down again.
Does this involve threading or can it be achieved with a simple time.sleep() function?
You could probably accomplish it with threading really elegantly but if you need a quick fix you could try
import time
timer = 15 * 60 # 60 seconds times 15 mins
while timer > 0:
time.sleep(0.985) # don't sleep for a full second or else you'll be off
timer -= 1
if someCondition:
timer = 15 * 60
executeCode() # called when time is zero and while loop is exited
If the whole process is as simple as you say, I would go about it like this (semi-psuedo-code):
def run_every_fifteen_minutes():
pass
def should_reset_timer():
pass
def main():
timer = 0
while True:
time.sleep(1)
timer+=1
if should_reset_timer():
timer = 0
if timer == 15*60:
run_every_fifteen_minutes()
timer = 0
Note that this won't be exactly fifteen minutes in. It might be late by a few seconds. The sleep isn't guaranteed to sleep only 1 second and the rest of the loop will take some time, too. You could add a system time compare in there if you need it to be really accurate.
Thanks for the help everyone, your answers pointed me in the right direction. In the end I came up with:
#!/usr/bin/python
import RPi.GPIO as GPIO
import time
import subprocess
GPIO.setmode(GPIO.BCM)
PIR_PIN = 4
GPIO.setup(PIR_PIN, GPIO.IN)
timer = 15 * 60 # 60 seconds times 15 mins
subprocess.call("sudo /opt/vc/bin/tvservice -o", shell=True)
try :
print "Screen Timer (CTRL+C to exit)"
time.sleep(5)
print "Ready..."
while True:
time.sleep(0.985)
# Test PIR_PIN condition
current_state = GPIO.input(PIR_PIN)
if timer > 0:
timer -= 1
if current_state: #is true
# Reset timer
timer = 15 * 60
else:
if current_state: #is true
subprocess.call("sudo /opt/vc/bin/tvservice -p", shell=True)
# Reset timer
timer = 15 * 60
else:
subprocess.call("sudo /opt/vc/bin/tvservice -o", shell=True)
except KeyboardInterrupt:
print "Quit"
GPIO.cleanup()
To put it in context, I'm using a PIR sensor to detect motion and switch on an hdmi connected monitor on a Raspberry Pi. After 15 mins of no movement I want to switch the monitor off and then if (at a later time) movement is detected, switch it back on again and restart the time.
The description sounds similar to a dead main's switch / watchdog timer. How it is implemented depends on your application: whether there is an event loop, are there blocking functions, do you need a separate process for proper isolation, etc. If no function is blocking in your code:
#!/usr/bin/env python3
import time
from time import time as timer
timeout = 900 # 15 minutes in seconds
countdown = timeout # reset the count
while True:
time.sleep(1 - timer() % 1) # lock with the timer, to avoid drift
countdown -= 1
if should_reset_count():
countdown = timeout # reset the count
if countdown <= 0: # timeout happened
countdown = timeout # reset the count
"some code is executed"
The code assumes that the sleep is never interrupted (note: before Python 3.5, the sleep may be interrupted by a signal). The code also assumes no function takes significant (around a second) time. Otherwise, you should use an explicit deadline instead (the same code structure):
deadline = timer() + timeout # reset
while True:
time.sleep(1 - timer() % 1) # lock with the timer, to avoid drift
if should_reset_count():
deadline = timer() + timeout # reset
if deadline < timer(): # timeout
deadline = timer() + timeout # reset
"some code is executed"
What is the best way to repeatedly execute a function every x seconds in Python?
How to run a function periodically in python
Maybe you should look into the Linux tool cron to schedule the execution of your script.
Related
Hi I am trying to add a timer to my power up in the game. In space invaders, when the core hits 500 I added it so that you gain an extra gun, but this is infinite and I only want to it to go for ten seconds. I tried the threading library which didn't work for e with object oriented programming, any suggestions?
You can try this:
import time
time_in_seconds = 10
def countdown(t):
while t:
mins, secs = divmod(t, 60)
timer = '{:02d}:{:02d}'.format(mins, secs)
print(timer, end="\r")
time.sleep(1)
t -= 1
countdown(time_in_seconds)
for more details, check out this LINK
I have a script that will scrape Facebook post in a while loop. But to prevent getting banned by Facebook I prefer the scraping function run(self) only run at a certain time and stop after 1 hour. How can I achieve that? I saw someone post about starting a function at a certain time but not stopping it after a specific hour.
Code to start a function at a certain time:
import schedule
import time
def job(t):
print ("I'm working...", t)
return
schedule.every().day.at("18:44").do(job,'It is 01:00')
while True:
schedule.run_pending()
time.sleep(60) # wait one minute
My script code
def run(self):
while True:
try:
wanted = "Pecahan setiap negeri (Kumulatif):" # wanted post
for post in get_posts("myhealthkkm", pages=5):
if post.get("post_text") is not None and wanted in post.get("post_text"):
# print("Found", t)
listposts.append(post.get("post_text"))
# append until 3 page finish then go here
time.sleep(1)
print(listposts)
global listView
if listposts != 0:
listView = listposts.copy()
print(listView)
listposts.clear()
except exceptions.TemporarilyBanned:
print("Temporarily banned, sleeping for 10m")
time.sleep(600)
I want the run() function only execute at 3pm and stop after 1 hour which is 4pm everyday. How can I achieve this goal ? Thanks
Thanks to the respond from #larsks, I tried to put a time check inside the function and exit the loop if it reached 3600second which is equal to 1 hour.
Here is the sample code:
import schedule
import time
def job():
program_starts = time.time()
while True:
now = time.time()
timeframe = now - program_starts
print("It has been {0} seconds since the loop started".format(timeframe))
if timeframe > 3600:
break
schedule.every().day.at("19:20:30").do(job)
while True:
schedule.run_pending()
#time.sleep(60) # wait one minute
I'm very new to code and want the led.off portion to be extendable. Basically, if I hit the button again before the 10 seconds run out. So if the button is hit before lighting up, there is another 10 second wait, starting at press 2.
from time import time, sleep
from signal import pause
led = LED(18) # or whatever pin you've got it on
button = Button(23) # again, adjust as necessary
def light_off_for_10_sec():
led.off()
sleep(10)
led.on()
button.when_pressed = light_off_for_10_sec
The 10 second pause before lighting up works great, but here is what I have tried to use to stretch the led.off period.
def stretched(values):
when_pressed = 10
for value in values:
if value:
sleep(5)
pressed = time()
yield time() - pressed <= 20
led.source = stretched(button.pressed)
pause()```
I trying to create a timer for my quiz game. It should reset after every right question. But problem with my code is that it keeps increasing speed after every time it resets.
timeCount = 30
def countdown():
global timeCount
while timeCount > 0:
print(timeCount)
sleep(1)
timeCount -= 1
else:
print("Time Out!")
I think this is what you are trying to do:
import time
timeCount = 30
start = time.time()
seconds = 0
def countdown():
global timeCount
global seconds
while seconds < timeCount:
now = time.time()
seconds = now - start
print(timeCount - seconds)
else:
print("Time Out!")
countdown()
This teaches you how to use time.time. You can take away seconds from timeCount to make a timer that goes down from 30 to 0. When the seconds hits 30, you can end the loop and print "Time out". You can truncate the unnecessary floating point values, since i am assuming floating point numbers doesn't look good on a quiz timer and is unnecessary as well.
seconds = int(seconds)
You can use the function time.perf_counter() :
import time
start=time.perf_counter()
time.sleep(1) #you can replace the sleep function with the action you want to monitor
end=time.perf_counter()
print('elapsed time : ',end-start)
In the example above, time.perf_counter() evaluated the time when it is called so it gives you the elapsed time between the two call.
if you want to use your current logic :
Your 'global' statement means that your are going to modify the 'timeCount' variable during the execution of your code. To fix it, you can use a new local variable in your function (called 'local_count' in the below solution), like this you reset the countdown each time you call your function :
import time
timeCount = 30
def countdown():
local_count = timeCount
while local_count > 0:
print(local_count)
time.sleep(1)
local_count -= 1
print("Time Out!")
I have a raspberry PI 2. With a relay board, what i use to for a switch sequence (like a traffic light).
I use a tool, called "webiopi" what create buttons on a website. When the button is clicked the function of the python script below is started.
What i want is to break out of the loop (or pause it) when another button is clicked. However, as long this loop is running, the tool don't look at the webpage
A kind of similar question is asked here Exiting a continuous loop in python via webiopi but this is for a single event and the solution doesn't work in my case.
Question is. How can I make this script look at a button what is clicked (can be a gpio switch as well) while the loop is running
GPIO_nek=11
GPIO_schouder=12
GPIO_rug1=8
GPIO_ONOFF=18
interval1 = 2
interval2 = 4
for x in range(0, 20):
GPIO.digitalWrite(GPIO_nek, GPIO.LOW)
time.sleep(interval1)
GPIO.digitalWrite(GPIO_schouder, GPIO.LOW)
time.sleep(interval1)
GPIO.digitalWrite(GPIO_nek, GPIO.HIGH)
time.sleep(interval1)
GPIO.digitalWrite(GPIO_rug1, GPIO.LOW)
time.sleep(interval2)
GPIO.digitalWrite(GPIO_schouder, GPIO.HIGH)
if (GPIO.digitalRead(GPIO_ONOFF) == GPIO.LOW):
GPIO.digitalWrite(GPIO_ONOFF, GPIO.HIGH)
break
When monitoring a real time event such as sensors or your button your best solution will be setting up a separate thread or process that contains nothing but an infinite loop that watches the resource and sets a flag when something interesting happens.
The example below sets up a process that automatically takes a picture on the RPI aprox. every minute.
#!/usr/bin/python
#Threading Prototype - Running a background thread that will take
# pictures at the appropriate time
#------------------------------------------------------------------
from multiprocessing import Queue
from multiprocessing import Process
from time import sleep
from datetime import datetime
from datetime import timedelta
from subprocess import call
#Doing the work ---------------------------------------------------
#Global Variables ---
messages = Queue()
start_time = datetime.now()
#Returns number of Milliseconds since start of program
def milliSinceStart():
global start_time
dt = datetime.now() - start_time
ms = (dt.days * 24 * 60 * 60 + dt.seconds) * 1000 + dt.microseconds / 1000.0
return ms
#Process Methods --------------------------------------------------
def processMessages():
print "Message Processor Launched"
while True:
print messages.get() #should halt until message in queue
sleep(0.1) #sleep for a tick just to avoid a run away process
def processPicutres():
print "Picture Taker Launched"
pictureCycleStart = milliSinceStart()
index = 0
while True:
if milliSinceStart() - pictureCycleStart > 10000: #once a minute
a = "blip" + str(index) + ".jpg"
b = "raspistill -n -t 100 -o " + a
messages.put("Click")
call ([b], shell=True)
messages.put("picture taken - " + b)
index = index + 1
pictureCycleStart = milliSinceStart()
sleep(0.1) #wait a tick -- don't hog processor time
def main():
print "MultiProcessing Prototype"
print "Launching message process"
Process(target=processMessages).start()
print "Back from launch"
print "Launching picture taking process"
Process(target=processPicutres).start()
print "Back from launch"
cycleStart = milliSinceStart()
index = 0
while True:
if milliSinceStart() - cycleStart > 1000:
messages.put("Tick " + str(index))
cycleStart = milliSinceStart()
index = index + 1
if __name__ == "__main__":
main()
The main method launches the Messaging and Picture processes and then sets up its own little infinite loop that does nothing more that display the message "Tick" every second. The picture process sets up a separate infinite loop, watching the clock and taking a picture periodically. The Message process monitors the picture process (again, an infinite loop) and when it detects that a picture has been taken, it outputs the fact to the screen.
The important part of this for your purpose is the message queue. The process queue is what is allowing the Picture and Message processes to communicate.
And because the task take place in different processes, it matters not if one process pauses as the others are always active. If you set up a button monitor process you can be checking message queue for this fact and halting your main program when the button is pressed. This pause in the main program would not effect the button process which could then pick up on the fact that the button is pressed again.
If the button is the GPIO switch as you mentioned at the end of the question, instead of the webpage button, then you can make use of an inbuilt GPIO interrupt function that saves your computer the resouces of constant polling:
import RPi.GPIO as GPIO
from threading import Event # We'll use it like time.sleep, but we can interrupt it.
GPIO_nek=11
GPIO_schouder=12
GPIO_rug1=8
GPIO_ONOFF=18
interval1 = 2
interval2 = 4
GPIO.setup(GPIO_ONOFF, GPIO.IN, pull_up_down=GPIO.PUD_UP)
done = False # loop control
timer = Event()
def quit_loop(): # Called by inbuilt threaded interrupt
global done
done = True
timer.set() # Interrupt the waiting
GPIO.add_event_detect(GPIO_ONOFF, GPIO.FALLING, callback=quit_loop, bouncetime=300) # Setup interrupt to call quit_loop
Because you're using this to break out of a loop, you want to shorten that loop to a single process:
tasks = [
(GPIO_nek, GPIO.LOW, interval1),
(GPIO_schouder, GPIO.LOW, interval1),
(GPIO_nek, GPIO.HIGH, interval1),
(GPIO_rug1, GPIO.LOW, interval2),
(GPIO_schouder, GPIO.HIGH, 0) ]
for pin, level, interval in tasks * 20: # Above you ran it 20 times, this notation keeps it in a single loop to break our o
if not done:
GPIO.digitalWrite(pin, level)
timer.wait(interval)
else:
timer.clear()
break
By using the threading Event().wait() and .set() instead of the standard time.sleep() you won't even have to wait for the sleep interval to finish.