How to make a pausable timer in python?

Question

I want to create a timer in python with the following functions:

timer.start() - should start the timer

timer.pause() - should pause the timer

timer.resume() - should resume the timer

timer.get() - should return the current time

The timer should run from 0 upwards. It is meant to measure time, not trigger a callback function.

So if you start it, it should start counting the seconds like 0 1 2 3, if you pause it, it should be stilll at 3, but not going further. After its resumed it then goes on with 4 5 6 and so on

How can I do this?

---

Pause/Resume functions for timer is not a duplicate because I do not care about callbacks.

Answer 1

# mytimer.py
from datetime import datetime
import time

class MyTimer():
    """
    timer.start() - should start the timer
    timer.pause() - should pause the timer
    timer.resume() - should resume the timer
    timer.get() - should return the current time
    """

    def __init__(self):
        print('Initializing timer')
        self.timestarted = None
        self.timepaused = None
        self.paused = False

    def start(self):
        """ Starts an internal timer by recording the current time """
        print("Starting timer")
        self.timestarted = datetime.now()

    def pause(self):
        """ Pauses the timer """
        if self.timestarted is None:
            raise ValueError("Timer not started")
        if self.paused:
            raise ValueError("Timer is already paused")
        print('Pausing timer')
        self.timepaused = datetime.now()
        self.paused = True

    def resume(self):
        """ Resumes the timer by adding the pause time to the start time """
        if self.timestarted is None:
            raise ValueError("Timer not started")
        if not self.paused:
            raise ValueError("Timer is not paused")
        print('Resuming timer')
        pausetime = datetime.now() - self.timepaused
        self.timestarted = self.timestarted + pausetime
        self.paused = False

    def get(self):
        """ Returns a timedelta object showing the amount of time
            elapsed since the start time, less any pauses """
        print('Get timer value')
        if self.timestarted is None:
            raise ValueError("Timer not started")
        if self.paused:
            return self.timepaused - self.timestarted
        else:
            return datetime.now() - self.timestarted

if __name__ == "__main__":
    t = MyTimer()
    t.start()
    print('Waiting 2 seconds'); time.sleep(2)
    print(t.get())
    print('Waiting 1 second'); time.sleep(1)
    t.pause()
    print('Waiting 2 seconds [paused]'); time.sleep(2)
    print(t.get())
    print('Waiting 1 second [paused]'); time.sleep(1)
    print(t.get())
    print('Waiting 1 second [paused]'); time.sleep(1)
    t.resume()
    print('Waiting 1 second'); time.sleep(1)
    print(t.get())

Run

python mytimer.py

Output

Initializing timer
Starting timer
Waiting 2 seconds
Get timer value
0:00:02.001523
Waiting 1 second
Pausing timer
Waiting 2 seconds [paused]
Get timer value
0:00:03.004724
Waiting 1 second [paused]
Get timer value
0:00:03.004724
Waiting 1 second [paused]
Resuming timer
Waiting 1 second
Get timer value
0:00:04.008578