Python | How to time the program

This article aims to show how to calculate the time it takes to perform various tasks.
A simple solution to it is to use time module. This module contains various time-related functions. Also it's very useful to put a higher-level interface over these functions and use them as a stop-watch as explained in the code below -

Code #1 :

Python3

# Using time module
import time

# defining the class
class Timer:
    
def __init__(self, func = time.perf_counter):
    self.elapsed = 0.0
    self._func = func
    self._start = None

# starting the module
def start(self):
    if self._start is not None:
        raise RuntimeError('Already started')
    self._start = self._func()

# stopping the timer
def stop(self):
    if self._start is None:
        raise RuntimeError('Not started')
    end = self._func()
    self.elapsed += end - self._start
    self._start = None

# resetting the timer
def reset(self):
    self.elapsed = 0.0
    @property

def running(self):
    return self._start is not None

def __enter__(self):
    self.start()
    return self

def __exit__(self, *args):
    self.stop()

We can start, stopped or reset this timer using this class as needed by the user so as to keep a track of the total elapsed time in the elapsed attribute. To do so, it is mentioned in the code below -

Code #2 :

Python3

# using the class Timer()
def countdown(n):
    while n > 0:
        n -= 1
        
# Use 1: Explicit start / stop
time = Timer()

# start
time.start()
countdown(1000000)

# stop
time.stop()
print(time.elapsed)

# Use 2: As a context manager
with time:
    countdown(1000000)
    
print(time.elapsed)

with Timer() as t2:
    countdown(1000000)
    
print(t2.elapsed)

The code above gives a very simple but still very useful class for measuring the time and tracking elapsed time.
It also illustrated how to support contextmanagement protocol and the with statement.
The underlying time function is a concern while performing the time functions. As the accuracy of timing measurements made with functions such as time.time() or time.clock() varies according to the operating system.
The highest-resolution timer available on the system in contrast is used by time.perf_counter().

To amount the CPU time used by process, time.process_time() is used instead as explained in the code below:

Code #3 :

Python3

t = Timer(time.process_time)
with t:
    countdown(1000000)
print(t.elapsed)

Both the time.perf_counter() and time.process_time() return a “time” in fractional seconds. To make sense of the results, call the functions twice and compute a time difference as the actual value of the time doesn’t have any particular meaning.

Python | How to time the program

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