How to measure time taken between lines of code in python?

So in Java, we can do https://stackoverflow.com/questions/313893/how-to-measure-time-taken-by-a-function-to-execute

But how is it done in python? To measure the time start and end time between lines of codes? Something that does this:

import some_time_library

starttime = some_time_library.some_module()
code_tobe_measured() 
endtime = some_time_library.some_module()

time_taken = endtime - starttime

If you want to measure CPU time, can use time.process_time() for Python 3.3 and above:

import time
start = time.process_time()
# your code here    
print(time.process_time() - start)

First call turns the timer on, and second call tells you how many seconds have elapsed.

There is also a function time.clock(), but it is deprecated since Python 3.3 and will be removed in Python 3.8.

There are better profiling tools like timeit and profile, however time.process_time() will measure the CPU time and this is what you're are asking about.

If you want to measure wall clock time instead, use time.time().

You can also use time library:

import time

start = time.time()

# your code

# end

print(f'Time: {time.time() - start}')

With a help of a small convenience class, you can measure time spent in indented lines like this:

with CodeTimer():
   line_to_measure()
   another_line()
   # etc...

Which will show the following after the indented line(s) finishes executing:

Code block took: x.xxx ms

UPDATE: You can now get the class with pip install linetimer and then from linetimer import CodeTimer. See this GitHub project.

The code for above class:

import timeit

class CodeTimer:
    def __init__(self, name=None):
        self.name = " '"  + name + "'" if name else ''

    def __enter__(self):
        self.start = timeit.default_timer()

    def __exit__(self, exc_type, exc_value, traceback):
        self.took = (timeit.default_timer() - self.start) * 1000.0
        print('Code block' + self.name + ' took: ' + str(self.took) + ' ms')

You could then name the code blocks you want to measure:

with CodeTimer('loop 1'):
   for i in range(100000):
      pass

with CodeTimer('loop 2'):
   for i in range(100000):
      pass

Code block 'loop 1' took: 4.991 ms
Code block 'loop 2' took: 3.666 ms

And nest them:

with CodeTimer('Outer'):
   for i in range(100000):
      pass

   with CodeTimer('Inner'):
      for i in range(100000):
         pass

   for i in range(100000):
      pass

Code block 'Inner' took: 2.382 ms
Code block 'Outer' took: 10.466 ms

Regarding timeit.default_timer(), it uses the best timer based on OS and Python version, see this answer.

I always prefer to check time in hours, minutes and seconds (%H:%M:%S) format:

from datetime import datetime
start = datetime.now()
# your code
end = datetime.now()
time_taken = end - start
print('Time: ',time_taken) 

output:

Time:  0:00:00.000019

Putting the code in a function, then using a decorator for timing is another option. (Source) The advantage of this method is that you define timer once and use it with a simple additional line for every function.

First, define timer decorator:

import functools
import time

def timer(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        start_time = time.perf_counter()
        value = func(*args, **kwargs)
        end_time = time.perf_counter()
        run_time = end_time - start_time
        print("Finished {} in {} secs".format(repr(func.__name__), round(run_time, 3)))
        return value

    return wrapper

Then, use the decorator while defining the function:

@timer
def doubled_and_add(num):
    res = sum([i*2 for i in range(num)])
    print("Result : {}".format(res))

Let's try:

doubled_and_add(100000)
doubled_and_add(1000000)

Output:

Result : 9999900000
Finished 'doubled_and_add' in 0.0119 secs
Result : 999999000000
Finished 'doubled_and_add' in 0.0897 secs

Note: I'm not sure why to use time.perf_counter instead of time.time. Comments are welcome.

I was looking for a way how to output a formatted time with minimal code, so here is my solution. Many people use Pandas anyway, so in some cases this can save from additional library imports.

import pandas as pd
start = pd.Timestamp.now()
# code
print(pd.Timestamp.now()-start)

Output:

0 days 00:05:32.541600

I would recommend using this if time precision is not the most important, otherwise use time library:

%timeit pd.Timestamp.now() outputs 3.29 µs ± 214 ns per loop

%timeit time.time() outputs 154 ns ± 13.3 ns per loop

You can try this as well:

from time import perf_counter

t0 = perf_counter()

...

t1 = perf_counter()
time_taken = t1 - t0

Let me add a little more to https://stackoverflow.com/a/63665115/7412781 solution.

• Removed dependency on functools.
• Used process time taken time.process_time() instead of absolute counter of time.perf_counter() because the process can be context switched out via kernel.
• Used the raw function pointer print to get the correct class name as well.

This is the decorator code.

import time

def decorator_time_taken(fnc):
    def inner(*args):
        start = time.process_time()
        ret = fnc(*args)
        end = time.process_time()
        print("{} took {} seconds".format(fnc, round((end - start), 6)))
        return ret
    return inner

This is the usage sample code. It's checking if 193939 is prime or not.

class PrimeBrute:
    @decorator_time_taken
    def isPrime(self, a):
        for i in range(a-2):
           if a % (i+2) == 0: return False
        return True

inst = PrimeBrute()
print(inst.isPrime(193939))

This is the output.

<function PrimeBrute.isPrime at 0x7fc0c6919ae8> took 0.015789 seconds
True

Use timeit module to benchmark your performance:

def test():
    print("test")
    emptyFunction()
    for i in [x for x in range(10000)]:
        i**i


def emptyFunction():
    pass

if __name__ == "__main__":
    import timeit
    print(timeit.timeit("test()", number = 5, globals = globals()))
    #print(timeit.timeit("test()", setup = "from __main__ import test",
    #    number = 5))

the first parameter defines the piece of code which we want to execute test in this case & number defines how many times you want to repeat the execution.

Output:

test
test
test
test
test
36.81822113099952

Using the module time, we can calculate unix time at the start of the function and at the end of a function. Here is how the code might look like:

from time import time as unix

This code imports time.time which allows us to calculate unix time.

from time import sleep

This is not mandatory, but I am also importing time.sleep for one of the demonstrations.

START_TIME = unix()

This is what calculates unix time and puts it in a variable. Remember, the function unix is not an actual function. I imported time.time as unix, so if you did not put as unix in the first import, you will need to use time.time().

After this, we put whichever function or code we want. At the end of the code snippet we put

TOTAL_TIME = unix()-START_TIME

This line of code does two things: It calculates unix time at the end of the function, and using the variable START_TIME from before, we calculate the amount of time it took to execute the code snippet.

We can then use this variable wherever we want, including for a print() function.

print("The snippet took {} seconds to execute".format(TOTAL_TIME))

Here I wrote a quick demonstration code that has two experiments as a demonstration. (Fully commented)

from time import time as unix # Import the module to measure unix time
from time import sleep

# Here are a few examples:
# 1. Counting to 100 000
START_TIME = unix()
for i in range(0, 100001):
  print("Number: {}\r".format(i), end="")
TOTAL_TIME = unix() - START_TIME
print("\nFinal time (Expirement 1): {} s\n".format(TOTAL_TIME))

# 2. Precision of sleep
for i in range(10):
  START_TIME = unix()
  sleep(0.1)
  TOTAL_TIME = unix() - START_TIME
  print("Sleep(0.1): Index: {}, Time: {} s".format(i,TOTAL_TIME))

Here was my output:

Number: 100000
Final time (Expirement 1): 16.666812419891357 s

Sleep(0.1): Index: 0, Time: 0.10014867782592773 s
Sleep(0.1): Index: 1, Time: 0.10016226768493652 s
Sleep(0.1): Index: 2, Time: 0.10202860832214355 s
Sleep(0.1): Index: 3, Time: 0.10015869140625 s
Sleep(0.1): Index: 4, Time: 0.10014724731445312 s
Sleep(0.1): Index: 5, Time: 0.10013675689697266 s
Sleep(0.1): Index: 6, Time: 0.10014677047729492 s
Sleep(0.1): Index: 7, Time: 0.1001439094543457 s
Sleep(0.1): Index: 8, Time: 0.10044598579406738 s
Sleep(0.1): Index: 9, Time: 0.10014700889587402 s
>