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Python | How to time the program

  • Difficulty Level : Medium
  • Last Updated : 23 Sep, 2021

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.
 


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