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

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.

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.

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}')