How to measure elapsed time in Python

Question

What I want is to start counting time somewhere in my code and then get the passed time  to measure the time it took to execute few function  I think I m using the timeit module wrong  but the docs are just confusing for me   import timeit  start   timeit timeit   print  hello   end   timeit timeit   print end - start

User · Answer

The python cProfile and pstats modules offer great support for measuring time elapsed in certain functions without having to add any code around the existing functions.

For example if you have a python script timeFunctions.py:

import time

def hello():
    print "Hello :)"
    time.sleep(0.1)

def thankyou():
    print "Thank you!"
    time.sleep(0.05)

for idx in range(10):
    hello()

for idx in range(100):
    thankyou()

To run the profiler and generate stats for the file you can just run:

python -m cProfile -o timeStats.profile timeFunctions.py

What this is doing is using the cProfile module to profile all functions in timeFunctions.py and collecting the stats in the timeStats.profile file. Note that we did not have to add any code to existing module (timeFunctions.py) and this can be done with any module.

Once you have the stats file you can run the pstats module as follows:

python -m pstats timeStats.profile

This runs the interactive statistics browser which gives you a lot of nice functionality. For your particular use case you can just check the stats for your function. In our example checking stats for both functions shows us the following:

Welcome to the profile statistics browser.
timeStats.profile% stats hello
<timestamp>    timeStats.profile

         224 function calls in 6.014 seconds

   Random listing order was used
   List reduced from 6 to 1 due to restriction <'hello'>

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
       10    0.000    0.000    1.001    0.100 timeFunctions.py:3(hello)

timeStats.profile% stats thankyou
<timestamp>    timeStats.profile

         224 function calls in 6.014 seconds

   Random listing order was used
   List reduced from 6 to 1 due to restriction <'thankyou'>

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
      100    0.002    0.000    5.012    0.050 timeFunctions.py:7(thankyou)

The dummy example does not do much but give you an idea of what can be done. The best part about this approach is that I dont have to edit any of my existing code to get these numbers and obviously help with profiling.

User · Answer

Use profiler module  It gives a very detailed profile   import profile profile run  main       it outputs something like             5 function calls in 0 047 seconds     Ordered by  standard name     ncalls  tottime  percall  cumtime  percall filename lineno function          1    0 000    0 000    0 000    0 000  0 exec          1    0 047    0 047    0 047    0 047  0 setprofile          1    0 000    0 000    0 000    0 000  lt string gt  1  lt module gt           0    0 000             0 000          profile 0 profiler          1    0 000    0 000    0 047    0 047 profile 0 main            1    0 000    0 000    0 000    0 000 two sum py 2 twoSum    I ve found it very informative

User · Answer

I prefer this  timeit doc is far too confusing    from datetime import datetime   start time   datetime now       INSERT YOUR CODE   time elapsed   datetime now   - start time   print  Time elapsed  hh mm ss ms      format time elapsed     Note  that there isn t any formatting going on here  I just wrote hh mm ss into the printout so one can interpret time elapsed

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This unique class-based approach offers a printable string representation  customizable rounding  and convenient access to the elapsed time as a string or a float  It was developed with Python 3 7   import datetime import timeit   class Timer         Measure time used           Ref  https   stackoverflow com a 57931660       def   init   self  round ndigits  int   0           self  round ndigits   round ndigits         self  start time   timeit default timer        def   call   self  - gt  float          return timeit default timer   - self  start time      def   str   self  - gt  str          return str datetime timedelta seconds round self    self  round ndigits      Usage     Setup timer  gt  gt  gt  timer   Timer      Access as a string  gt  gt  gt  print f Time elapsed is  timer     Time elapsed is 0 00 03   gt  gt  gt  print f Time elapsed is  timer     Time elapsed is 0 00 04     Access as a float  gt  gt  gt  timer   6 841332235  gt  gt  gt  timer   7 970274425

User · Answer

To get insight on every function calls recursively  do    load ext snakeviz   snakeviz   It just takes those 2 lines of code in a Jupyter notebook  and it generates a nice interactive diagram  For example      Here is the code  Again  the 2 lines starting with   are the only extra lines of code needed to use snakeviz       pip install snakeviz  load ext snakeviz import glob import hashlib    snakeviz  files   glob glob    txt   def print files hashed files       for file in files          with open file  as f              print hashlib md5 f read   encode  utf-8    hexdigest    print files hashed files    It also seems possible to run snakeviz outside notebooks  More info on the snakeviz website

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Here s another way to do this    gt  gt  from pytictoc import TicToc  gt  gt  t   TicToc     create TicToc instance  gt  gt  t tic     Start timer  gt  gt    do something  gt  gt  t toc     Print elapsed time Elapsed time is 2 612231 seconds    Comparing with traditional way    gt  gt  from time import time  gt  gt  t1   time    gt  gt    do something  gt  gt  t2   time    gt  gt  elapsed   t2 - t1  gt  gt  print  Elapsed time is  f seconds     elapsed  Elapsed time is 2 612231 seconds    Installation   pip install pytictoc   Refer to the PyPi page for more details

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If you just want to measure the elapsed wall-clock time between two points  you could use  time time     import time  start   time time   print  hello   end   time time   print end - start    This gives the execution time in seconds   Another option since 3 3 might be to use perf counter or process time  depending on your requirements  Before 3 3 it was recommended to use time clock  thanks Amber   However  it is currently deprecated      On Unix  return the current processor time as a floating point number   expressed in seconds  The precision  and in fact the very definition   of the meaning of    processor time     depends on that of the C function   of the same name       On Windows  this function returns wall-clock seconds elapsed since the   first call to this function  as a floating point number  based on the   Win32 function QueryPerformanceCounter    The resolution is typically   better than one microsecond       Deprecated since version 3 3  The behaviour of this function depends   on the platform  use perf counter   or process time   instead    depending on your requirements  to have a well defined behaviour

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Using time time to measure execution gives you the overall execution time of your commands including running time spent by other processes on your computer  It is the time the user notices  but is not good if you want to compare different code snippets   algorithms   functions        More information on timeit    Using the timeit Module timeit     Time the execution of small bits of Python code   If you want a deeper insight into profiling    http   wiki python org moin PythonSpeed PerformanceTips Profiling Code How can you profile a python script    Update  I used http   pythonhosted org line profiler  a lot during the last year and find it very helpfull and recommend to use it instead of Pythons profile module

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It s fun to do this with a context-manager that automatically remembers the start time upon entry to a with block  then freezes the end time on block exit  With a little trickery  you can even get a running elapsed-time tally inside the block from the same context-manager function    The core library doesn t have this  but probably ought to   Once in place  you can do things like   with elapsed timer   as elapsed        some lengthy code     print   midpoint at   2f seconds    elapsed        time so far       other lengthy code  print   all done at   2f seconds    elapsed       Here s contextmanager code sufficient to do the trick   from contextlib import contextmanager from timeit import default timer   contextmanager def elapsed timer        start   default timer       elapser   lambda  default timer   - start     yield lambda  elapser       end   default timer       elapser   lambda  end-start   And some runnable demo code   import time  with elapsed timer   as elapsed      time sleep 1      print elapsed        time sleep 2      print elapsed        time sleep 3    Note that by design of this function  the return value of elapsed   is frozen on block exit  and further calls return the same duration  of about 6 seconds in this toy example

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Kind of a super later response  but maybe it serves a purpose for someone  This is a way to do it which I think is super clean   import time  def timed fun   args       s   time time       r   fun  args      print     execution took    seconds   format fun   name    time time  -s       return r   timed print   Hello     Keep in mind that  print  is a function in Python 3 and not Python 2 7  However  it works with any other function  Cheers

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Measure execution time of small code snippets      Unit of time  measured in seconds as a float   import timeit t   timeit Timer  li   list map lambda x x 2  1 2 3 4 5      t timeit   t repeat    gt  1 2934070999999676  1 3335035000000062  1 422568500000125       The repeat   method is a convenience to call timeit   multiple times and return a list of results   repeat repeat 3          With this list we can take a mean of all times       By default  timeit   temporarily turns off garbage collection during the timing  time Timer   solves this problem       Pros            timeit Timer   makes independent timings more comparable  The gc may be an important component of the performance of the function being measured  If so  gc garbage collector  can be re-enabled as the first statement in the setup string  For example      timeit Timer  li   list map lambda x x 2  1 2 3 4 5     setup  gc enable        Source Python Docs

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We can also convert time into human-readable time   import time  datetime  start   time clock    def num multi1 max       result   0     for num in range 0  1000           if  num   3    0 or num   5    0               result    num      print  Sum is  d     result  num multi1 1000   end   time clock   value   end - start timestamp   datetime datetime fromtimestamp value  print timestamp strftime   Y- m- d  H  M  S

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Time can also be measured by  timeit magic function as follow    timeit -t -n 1 print  hello     n 1 is for running function only 1 time

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I made a library for this  if you want to measure a function you can just do it like this    from pythonbenchmark import compare  measure import time  a b c d e   10 10 10 10 10 something    a b c d e    measure def myFunction something       time sleep 0 4    measure def myOptimizedFunction something       time sleep 0 2   myFunction input  myOptimizedFunction input    https   github com Karlheinzniebuhr pythonbenchmark

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The timeit module is good for timing a small piece of Python code  It can be used at least in three forms    1- As a command-line module  python2 -m timeit  for i in xrange 10   oct i      2- For a short code  pass it as arguments   import timeit timeit Timer  for i in xrange 10   oct i    timeit     3- For longer code as   import timeit code to test       a   range 100000  b      for i in a      b append i 2      elapsed time   timeit timeit code to test  number 100  100 print elapsed time

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Here s another context manager for timing code -  Usage    from benchmark import benchmark  with benchmark  Test 1 1        1 1   gt  Test 1 1   1 41e-06 seconds   or  if you need the time value  with benchmark  Test 1 1   as b      1 1 print b time    gt  Test 1 1   7 05e-07 seconds 7 05233786763e-07   benchmark py   from timeit import default timer as timer  class benchmark object        def   init   self  msg  fmt   0 3g            self msg   msg         self fmt   fmt      def   enter   self           self start   timer           return self      def   exit   self   args           t   timer   - self start         print    s       self fmt     seconds      self msg  t           self time   t   Adapted from http   dabeaz blogspot fr 2010 02 context-manager-for-timing-benchmarks html

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The only way I can think of is using time time     import time start   time time   sleep 5   just to give it some delay to show it working finish   time time   elapsed   finish - start print elapsed    Hope that will help

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on python3   from time import sleep  perf counter as pc t0   pc   sleep 1  print pc  -t0    elegant and short

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Here is a tiny timer class that returns  hh mm ss  string    class Timer    def   init   self       self start   time time      def restart self       self start   time time      def get time hhmmss self       end   time time       m  s   divmod end - self start  60      h  m   divmod m  60      time str     02d  02d  02d     h  m  s      return time str   Usage      Start timer my timer   Timer          do something    Get time string  time hhmmss   my timer get time hhmmss   print  Time elapsed   s    time hhmmss          use the timer again my timer restart          do something    Get time  time hhmmss   my timer get time hhmmss          etc

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With Ipython only  you can use  timeit to measure average processing time   def foo        print  hello    and then        timeit foo     the result is something like   10000 loops  best of 3  27   s per loop

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Measuring time in seconds   from timeit import default timer as timer from datetime import timedelta  start   timer   end   timer   print timedelta seconds end-start     Output   0 00 01 946339

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How to measure the time between two operations  Compare the time of two operations  import time  b    123 321  123 t1   time time    c     9999 123  321  123 t2   time time    print t2-t1   7 987022399902344e-05

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import time  def getElapsedTime startTime  units       elapsedInSeconds   time time   - startTime     if units     sec           return elapsedInSeconds     if units     min           return elapsedInSeconds 60     if units     hour           return elapsedInSeconds  60 60

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Given a function you d like to time   test py   def foo           print  hello         return  hello    the easiest way to use timeit is to call it from the command line     python -mtimeit -s import test   test foo    1000000 loops  best of 3  0 254 usec per loop   Do not try to use time time or time clock  naively  to compare the speed of functions  They can give misleading results   PS  Do not put print statements in a function you wish to time  otherwise the time measured will depend on the speed of the terminal

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I like it simple  python 3    from timeit import timeit  timeit lambda  print  hello      Output is microseconds for a single execution   2 430883963010274   Explanation  timeit executes the anonymous function 1 million times by default and the result is given in seconds  Therefore the result for 1 single execution is the same amount but in microseconds on average     For slow operations add a lower number of iterations or you could be waiting forever   import time  timeit lambda  time sleep 1 5   number 1    Output is always in seconds for the total number of iterations   1 5015795179999714

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If you want to be able to time functions conveniently  you can use a simple decorator   def timing decorator func       def wrapper  args    kwargs           start   time time           original return val   func  args    kwargs          end   time time           print  time elapsed in    func   name          end - start  sep             return original return val      return wrapper   You can use it on a function that you want to time like this    timing decorator def function to time        time sleep 1    Then any time you call function to time  it will print how long it took and the name of the function being timed

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Python 3 only  Since time clock   is deprecated as of Python 3 3  you will want to use time perf counter   for system-wide timing  or time process time   for process-wide timing  just the way you used to use time clock    import time  t   time process time    do some stuff elapsed time   time process time   - t  The new function process time will not include time elapsed during sleep

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based on the contextmanager solution given by https   stackoverflow com a 30024601 5095636  hereunder the lambda free version  as flake8 warns on the usage of lambda as per E731   from contextlib import contextmanager from timeit import default timer   contextmanager def elapsed timer        start time   default timer        class  Timer          start   start time       end   default timer         duration   end - start      yield  Timer      end time   default timer        Timer end   end time      Timer duration   end time - start time   test   from time import sleep  with elapsed timer   as t      print  start    t start      sleep 1      print  end    t end   t start t end t duration

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Although it s not strictly asked in the question  it is quite often the case that you want a simple  uniform way to incrementally measure the elapsed time between several lines of code  If you are using Python 3 8 or above  you can make use of assignment expressions  a k a  the walrus operator  to achieve this in a fairly elegant way  import time  start  times   time perf counter        print  quot hello quot   times  quot print quot     -start    start    time perf counter     time sleep 1 42  times  quot sleep quot     -start    start    time perf counter     a    n  2 for n in range 10000   times  quot pow quot     -start    start    time perf counter     print times     gt    print   2 193450927734375e-05   sleep   1 4210970401763916   power   0 005671024322509766

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You can use timeit   Here is an example on how to test naive func that takes parameter using Python REPL    gt  gt  gt  import timeit                                                                                            gt  gt  gt  def naive func x                                                                                               a   0                                                                                                      for i in range a                                                                                               a    i                                                                                                 return a                                                                                             gt  gt  gt  def wrapper func   args    kwargs                                                                              def wrapper                                                                                                    return func  args    kwargs                                                                            return wrapper                                                                                       gt  gt  gt  wrapped   wrapper naive func  1 000                                                                      gt  gt  gt  timeit timeit wrapped  number 1 000 000                                                                0 4458435332577161     You don t need wrapper function if function doesn t have any parameters

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In addition to  timeit in ipython you can also use   timeit for multi-line code snippets   In  1     timeit         complex func           2   2    5                  1 s    1 93 ms per loop  mean    std  dev  of 7 runs  1 loop each    Also it can be used in jupyter notebook the same way  just put magic   timeit at the beginning of cell

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Here s a pretty well documented and fully type hinted decorator I use as a general utility  from functools import wraps from time import perf counter from typing import Any  Callable  Optional  TypeVar  cast  F   TypeVar  quot F quot   bound Callable      Any     def timer prefix  Optional str    None  precision  int   6  - gt  Callable  F   F        quot  quot  quot Use as a decorator to time the execution of any function       Args          prefix  String to print before the time taken              Default is the name of the function          precision  How many decimals to include in the seconds value       Examples           gt  gt  gt   timer               def foo x                   return x          gt  gt  gt  foo 123          foo  0 000   s         123          gt  gt  gt   timer  quot Time taken   quot   2              def foo x                   return x          gt  gt  gt  foo 123          Time taken  0 00s         123       quot  quot  quot      def decorator func  F  - gt  F           wraps func          def wrapper  args  Any    kwargs  Any  - gt  Any              nonlocal prefix             prefix   prefix if prefix is not None else f quot  func   name      quot              start   perf counter               result   func  args    kwargs              end   perf counter               print f quot  prefix  end - start   precision f s quot               return result         return cast F  wrapper      return decorator  Example usage  from timer import timer    timer precision 9  def takes long x  int  - gt  bool      return x in  i for i in range x   1     result   takes long 10  8  print result    Output  takes long  4 942629056s True   The doctests can be checked with    python3 -m doctest --verbose -o ELLIPSIS timer py  And the type hints with    mypy timer py

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Here are my findings after going through many good answers here as well as a few other articles  First  if you are debating between timeit and time time  the timeit has two advantages   timeit selects the best timer available on your OS and Python version  timeit disables garbage collection  however  this is not something you may or may not want   Now the problem is that timeit is not that simple to use because it needs setup and things get ugly when you have a bunch of imports  Ideally  you just want a decorator or use with block and measure time  Unfortunately  there is nothing built-in available for this so you have two options  Option 1  Use timebudget library The timebudget is a versatile and very simple library that you can use just in one line of code after pip install   timebudget    Record how long this function takes def my method          my code  Option 2  Use my small module I created below little timing utility module called timing py  Just drop this file in your project and start using it  The only external dependency is runstats which is again small  Now you can time any function just by putting a decorator in front of it  import timing   timing MeasureTime def MyBigFunc         do something time consuming     for i in range 10000           print i   timing print all timings    If you want to time portion of code then just put it inside with block  import timing   somewhere in my code  with timing MeasureBlockTime  quot MyBlock quot         do something time consuming     for i in range 10000           print i     rest of my code  timing print all timings    Advantages  There are several half-backed versions floating around so I want to point out few highlights   Use timer from timeit instead of time time for reasons described earlier  You can disable GC during timing if you want  Decorator accepts functions with named or unnamed params  Ability to disable printing in block timing  use with timing MeasureBlockTime   as t and then t elapsed   Ability to keep gc enabled for block timing

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Use timeit default timer instead of timeit timeit  The former provides the best clock available on your platform and version of Python automatically   from timeit import default timer as timer  start   timer         end   timer   print end - start    Time in seconds  e g  5 38091952400282   timeit default timer is assigned to time time   or time clock   depending on OS  On Python 3 3  default timer is time perf counter   on all platforms  See Python - time clock   vs  time time   - accuracy   See also    Optimizing code How to optimize for speed

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The easiest way to calculate the duration of an operation  import time  start time   time monotonic   print time ctime      lt operations  programs gt   print  minutes     time monotonic   - start time  60

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print elapsed time function is below def print elapsed time prefix          e time   time time       if not hasattr print elapsed time   s time            print elapsed time s time   e time     else          print f  prefix  elapsed time   e time - print elapsed time s time  2f  sec           print elapsed time s time   e time  use it in this way print elapsed time        heavy jobs     print elapsed time  after heavy jobs        tons of jobs     print elapsed time  after tons of jobs    result is after heavy jobs elapsed time  0 39 sec after tons of jobs elapsed time  0 60 sec    the pros and cons of this function is that you don t need to pass start time

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One more way to use timeit   from timeit import timeit  def func        return 1   1  time   timeit func  number 1  print time

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