Python s time clock vs time time accuracy

Question

Which is better to use for timing in Python  time clock   or time time    Which one provides more accuracy   for example   start   time clock       do something elapsed    time clock   - start    vs   start   time time       do something elapsed    time time   - start

User · Answer

Others have answered re  time time   vs  time clock      However  if you re timing the execution of a block of code for benchmarking profiling purposes  you should take a look at the timeit module

User · Answer

Short answer  use time clock   for timing in Python   On  nix systems  clock   returns the processor time as a floating point number  expressed in seconds  On Windows  it returns the seconds elapsed since the first call to this function  as a floating point number   time   returns the the seconds since the epoch  in UTC  as a floating point number  There is no guarantee that you will get a better precision that 1 second  even though time   returns a floating point number   Also note that if the system clock has been set back between two calls to this function  the second function call will return a lower value

User · Answer

Depends on what you care about  If you mean WALL TIME  as in  the time on the clock on your wall   time clock   provides NO accuracy because it may manage CPU time

User · Answer

Right answer   They re both the same length of a fraction   But which faster if subject is time    A little test case    import timeit import time  clock list      time list       test1       def test v time clock         s   time clock   - v      test2       def test v time time         s   time time   - v     def test it Range        for i in range Range            clk   timeit timeit test1  number 10000          clock list append clk          tml   timeit timeit test2  number 10000          time list append tml   test it 100   print  Clock Min   f Max   f Average   f    min clock list   max clock list   sum clock list  float len clock list    print  Time  Min   f Max   f Average   f    min time list   max time list   sum time list  float len time list      I am not work an Swiss labs but I ve tested     Based of this question   time clock   is better than time time    Edit   time clock   is internal counter so can t use outside  got limitations max 32BIT FLOAT  can t continued counting if not store first last values  Can t merge another one counter

User · Answer

As of 3 3  time clock   is deprecated  and it s suggested to use time process time   or time perf counter   instead   Previously in 2 7  according to the time module docs      time clock        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  but in any case  this is the function to use for   benchmarking Python or timing algorithms       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    Additionally  there is the timeit module for benchmarking code snippets

User · Answer

The short answer is  most of the time time clock   will be better  However  if you re timing some hardware  for example some algorithm you put in the GPU   then time clock   will get rid of this time and time time   is the only solution left   Note  whatever the method used  the timing will depend on factors you cannot control  when will the process switch  how often        this is worse with time time   but exists also with time clock    so you should never run one timing test only  but always run a series of test and look at mean variance of the times

User · Answer

The difference is very platform-specific   clock   is very different on Windows than on Linux  for example   For the sort of examples you describe  you probably want the  timeit  module instead

User · Answer

On Unix time clock   measures the amount of CPU time that has been used by the current process  so it s no good for measuring elapsed time from some point in the past  On Windows it will measure wall-clock seconds elapsed since the first call to the function  On either system time time   will return seconds passed since the epoch    If you re writing code that s meant only for Windows  either will work  though you ll use the two differently - no subtraction is necessary for time clock     If this is going to run on a Unix system or you want code that is guaranteed to be portable  you will want to use time time

User · Answer

The difference is very platform-specific   clock   is very different on Windows than on Linux  for example   For the sort of examples you describe  you probably want the  timeit  module instead

User · Answer

To the best of my understanding  time clock   has as much precision as your system will allow it

User · Answer

time   has better precision than clock   on Linux  clock   only has precision less than 10 ms  While time   gives prefect precision  My test is on CentOS 6 4  python 2 6  using time     1 requests  response time  14 1749382019 ms 2 requests  response time  8 01301002502 ms 3 requests  response time  8 01491737366 ms 4 requests  response time  8 41021537781 ms 5 requests  response time  8 38804244995 ms   using clock     1 requests  response time  10 0 ms 2 requests  response time  0 0 ms  3 requests  response time  0 0 ms 4 requests  response time  10 0 ms 5 requests  response time  0 0 ms  6 requests  response time  0 0 ms 7 requests  response time  0 0 ms  8 requests  response time  0 0 ms

User · Answer

clock   -  floating point number  Return the CPU time or real time since the start of the process or since the first call to clock     This has as much precision as the system records   time   -  floating point number  Return the current time in seconds since the Epoch  Fractions of a second may be present if the system clock provides them   Usually time   is more precise  because operating systems do not store the process running time with the precision they store the system time  ie  actual time

User · Answer

Others have answered re  time time   vs  time clock      However  if you re timing the execution of a block of code for benchmarking profiling purposes  you should take a look at the timeit module

User · Answer

Short answer  use time clock   for timing in Python   On  nix systems  clock   returns the processor time as a floating point number  expressed in seconds  On Windows  it returns the seconds elapsed since the first call to this function  as a floating point number   time   returns the the seconds since the epoch  in UTC  as a floating point number  There is no guarantee that you will get a better precision that 1 second  even though time   returns a floating point number   Also note that if the system clock has been set back between two calls to this function  the second function call will return a lower value

User · Answer

The difference is very platform-specific   clock   is very different on Windows than on Linux  for example   For the sort of examples you describe  you probably want the  timeit  module instead

User · Answer

As of 3 3  time clock   is deprecated  and it s suggested to use time process time   or time perf counter   instead   Previously in 2 7  according to the time module docs      time clock        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  but in any case  this is the function to use for   benchmarking Python or timing algorithms       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    Additionally  there is the timeit module for benchmarking code snippets

User · Answer

As of 3 3  time clock   is deprecated  and it s suggested to use time process time   or time perf counter   instead   Previously in 2 7  according to the time module docs      time clock        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  but in any case  this is the function to use for   benchmarking Python or timing algorithms       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    Additionally  there is the timeit module for benchmarking code snippets

User · Answer

As others have noted time clock   is deprecated in favour of  time perf counter   or time process time    but Python 3 7 introduces nanosecond resolution timing with time perf counter ns    time process time ns    and time time ns    along with 3 other functions   These 6 new nansecond resolution functions are detailed in PEP 564      time clock gettime ns clock id       time clock settime ns clock id  time int       time monotonic ns        time perf counter ns        time process time ns        time time ns        These functions are similar to the version without the  ns suffix  but   return a number of nanoseconds as a Python int    As others have also noted  use the timeit module to time functions and small code snippets

User · Answer

Short answer  use time clock   for timing in Python   On  nix systems  clock   returns the processor time as a floating point number  expressed in seconds  On Windows  it returns the seconds elapsed since the first call to this function  as a floating point number   time   returns the the seconds since the epoch  in UTC  as a floating point number  There is no guarantee that you will get a better precision that 1 second  even though time   returns a floating point number   Also note that if the system clock has been set back between two calls to this function  the second function call will return a lower value

User · Answer

To the best of my understanding  time clock   has as much precision as your system will allow it

User · Answer

Others have answered re  time time   vs  time clock      However  if you re timing the execution of a block of code for benchmarking profiling purposes  you should take a look at the timeit module

User · Answer

On Unix time clock   measures the amount of CPU time that has been used by the current process  so it s no good for measuring elapsed time from some point in the past  On Windows it will measure wall-clock seconds elapsed since the first call to the function  On either system time time   will return seconds passed since the epoch    If you re writing code that s meant only for Windows  either will work  though you ll use the two differently - no subtraction is necessary for time clock     If this is going to run on a Unix system or you want code that is guaranteed to be portable  you will want to use time time

User · Answer

Depends on what you care about  If you mean WALL TIME  as in  the time on the clock on your wall   time clock   provides NO accuracy because it may manage CPU time

User · Answer

On Unix time clock   measures the amount of CPU time that has been used by the current process  so it s no good for measuring elapsed time from some point in the past  On Windows it will measure wall-clock seconds elapsed since the first call to the function  On either system time time   will return seconds passed since the epoch    If you re writing code that s meant only for Windows  either will work  though you ll use the two differently - no subtraction is necessary for time clock     If this is going to run on a Unix system or you want code that is guaranteed to be portable  you will want to use time time

User · Answer

As others have noted time clock   is deprecated in favour of  time perf counter   or time process time    but Python 3 7 introduces nanosecond resolution timing with time perf counter ns    time process time ns    and time time ns    along with 3 other functions   These 6 new nansecond resolution functions are detailed in PEP 564      time clock gettime ns clock id       time clock settime ns clock id  time int       time monotonic ns        time perf counter ns        time process time ns        time time ns        These functions are similar to the version without the  ns suffix  but   return a number of nanoseconds as a Python int    As others have also noted  use the timeit module to time functions and small code snippets

User · Answer

The short answer is  most of the time time clock   will be better  However  if you re timing some hardware  for example some algorithm you put in the GPU   then time clock   will get rid of this time and time time   is the only solution left   Note  whatever the method used  the timing will depend on factors you cannot control  when will the process switch  how often        this is worse with time time   but exists also with time clock    so you should never run one timing test only  but always run a series of test and look at mean variance of the times

User · Answer

The difference is very platform-specific   clock   is very different on Windows than on Linux  for example   For the sort of examples you describe  you probably want the  timeit  module instead

User · Answer

Depends on what you care about  If you mean WALL TIME  as in  the time on the clock on your wall   time clock   provides NO accuracy because it may manage CPU time

User · Answer

time clock   was removed in Python 3 8 because it had platform-dependent behavior    On Unix  return the current processor time as a floating point number expressed in seconds  On Windows  this function returns wall-clock seconds elapsed since the first call to this function  as a floating point number  print time clock     time sleep 10   print time clock      Linux     0 0382  0 0384     see Processor Time   Windows  26 1224 36 1566     see Wall-Clock Time    So which function to pick instead    Processor Time  This is how long this specific process spends actively being executed on the CPU  Sleep  waiting for a web request  or time when only other processes are executed will not contribute to this    Use time process time    Wall-Clock Time  This refers to how much time has passed  on a clock hanging on the wall   i e  outside real time    Use time perf counter     time time   also measures wall-clock time but can be reset  so you could go back in time time monotonic   cannot be reset  monotonic   only goes  forward  but has lower precision than time perf counter

User · Answer

I use this code to compare 2 methods  My OS is windows 8   processor core i5   RAM 4GB import time  def t time        start time time       time sleep 0 1      return  time time  -start    def t clock        start time clock       time sleep 0 1      return  time clock  -start      counter time 0 counter clock 0  for i in range 1 100       counter time    t time        for i in range 1 100           counter clock    t clock    print  quot time     quot  counter time 100 print  quot clock     quot  counter clock 100  output  time     0 0993799996376  clock     0 0993572257367

User · Answer

Right answer   They re both the same length of a fraction   But which faster if subject is time    A little test case    import timeit import time  clock list      time list       test1       def test v time clock         s   time clock   - v      test2       def test v time time         s   time time   - v     def test it Range        for i in range Range            clk   timeit timeit test1  number 10000          clock list append clk          tml   timeit timeit test2  number 10000          time list append tml   test it 100   print  Clock Min   f Max   f Average   f    min clock list   max clock list   sum clock list  float len clock list    print  Time  Min   f Max   f Average   f    min time list   max time list   sum time list  float len time list      I am not work an Swiss labs but I ve tested     Based of this question   time clock   is better than time time    Edit   time clock   is internal counter so can t use outside  got limitations max 32BIT FLOAT  can t continued counting if not store first last values  Can t merge another one counter

User · Answer

To the best of my understanding  time clock   has as much precision as your system will allow it

User · Answer

clock   -  floating point number  Return the CPU time or real time since the start of the process or since the first call to clock     This has as much precision as the system records   time   -  floating point number  Return the current time in seconds since the Epoch  Fractions of a second may be present if the system clock provides them   Usually time   is more precise  because operating systems do not store the process running time with the precision they store the system time  ie  actual time

User · Answer

Comparing test result between Ubuntu Linux and Windows 7   On Ubuntu   gt  gt  gt  start   time time    time sleep 0 5    time time   - start  0 5005500316619873   On Windows 7   gt  gt  gt  start   time time    time sleep 0 5    time time   - start  0 5

User · Answer

One thing to keep in mind    Changing the system time affects time time   but not time clock     I needed to control some automatic tests executions  If one step of the test case took more than a given amount of time  that TC was aborted to go on with the next one   But sometimes a step needed to change the system time  to check the scheduler module of the application under test   so after setting the system time a few hours in the future  the TC timeout expired and the test case was aborted  I had to switch from time time   to time clock   to handle this properly

User · Answer

time clock   was removed in Python 3 8 because it had platform-dependent behavior    On Unix  return the current processor time as a floating point number expressed in seconds  On Windows  this function returns wall-clock seconds elapsed since the first call to this function  as a floating point number  print time clock     time sleep 10   print time clock      Linux     0 0382  0 0384     see Processor Time   Windows  26 1224 36 1566     see Wall-Clock Time    So which function to pick instead    Processor Time  This is how long this specific process spends actively being executed on the CPU  Sleep  waiting for a web request  or time when only other processes are executed will not contribute to this    Use time process time    Wall-Clock Time  This refers to how much time has passed  on a clock hanging on the wall   i e  outside real time    Use time perf counter     time time   also measures wall-clock time but can be reset  so you could go back in time time monotonic   cannot be reset  monotonic   only goes  forward  but has lower precision than time perf counter

User · Answer

clock   -  floating point number  Return the CPU time or real time since the start of the process or since the first call to clock     This has as much precision as the system records   time   -  floating point number  Return the current time in seconds since the Epoch  Fractions of a second may be present if the system clock provides them   Usually time   is more precise  because operating systems do not store the process running time with the precision they store the system time  ie  actual time

User · Answer

Comparing test result between Ubuntu Linux and Windows 7   On Ubuntu   gt  gt  gt  start   time time    time sleep 0 5    time time   - start  0 5005500316619873   On Windows 7   gt  gt  gt  start   time time    time sleep 0 5    time time   - start  0 5

User · Answer

On Unix time clock   measures the amount of CPU time that has been used by the current process  so it s no good for measuring elapsed time from some point in the past  On Windows it will measure wall-clock seconds elapsed since the first call to the function  On either system time time   will return seconds passed since the epoch    If you re writing code that s meant only for Windows  either will work  though you ll use the two differently - no subtraction is necessary for time clock     If this is going to run on a Unix system or you want code that is guaranteed to be portable  you will want to use time time

User · Answer

Short answer  use time clock   for timing in Python   On  nix systems  clock   returns the processor time as a floating point number  expressed in seconds  On Windows  it returns the seconds elapsed since the first call to this function  as a floating point number   time   returns the the seconds since the epoch  in UTC  as a floating point number  There is no guarantee that you will get a better precision that 1 second  even though time   returns a floating point number   Also note that if the system clock has been set back between two calls to this function  the second function call will return a lower value

User · Answer

Others have answered re  time time   vs  time clock      However  if you re timing the execution of a block of code for benchmarking profiling purposes  you should take a look at the timeit module

User · Answer

To the best of my understanding  time clock   has as much precision as your system will allow it

User · Answer

As of 3 3  time clock   is deprecated  and it s suggested to use time process time   or time perf counter   instead   Previously in 2 7  according to the time module docs      time clock        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  but in any case  this is the function to use for   benchmarking Python or timing algorithms       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    Additionally  there is the timeit module for benchmarking code snippets

User · Answer

time   has better precision than clock   on Linux  clock   only has precision less than 10 ms  While time   gives prefect precision  My test is on CentOS 6 4  python 2 6  using time     1 requests  response time  14 1749382019 ms 2 requests  response time  8 01301002502 ms 3 requests  response time  8 01491737366 ms 4 requests  response time  8 41021537781 ms 5 requests  response time  8 38804244995 ms   using clock     1 requests  response time  10 0 ms 2 requests  response time  0 0 ms  3 requests  response time  0 0 ms 4 requests  response time  10 0 ms 5 requests  response time  0 0 ms  6 requests  response time  0 0 ms 7 requests  response time  0 0 ms  8 requests  response time  0 0 ms

User · Answer

The short answer is  most of the time time clock   will be better  However  if you re timing some hardware  for example some algorithm you put in the GPU   then time clock   will get rid of this time and time time   is the only solution left   Note  whatever the method used  the timing will depend on factors you cannot control  when will the process switch  how often        this is worse with time time   but exists also with time clock    so you should never run one timing test only  but always run a series of test and look at mean variance of the times

User · Answer

Depends on what you care about  If you mean WALL TIME  as in  the time on the clock on your wall   time clock   provides NO accuracy because it may manage CPU time

User · Answer

One thing to keep in mind    Changing the system time affects time time   but not time clock     I needed to control some automatic tests executions  If one step of the test case took more than a given amount of time  that TC was aborted to go on with the next one   But sometimes a step needed to change the system time  to check the scheduler module of the application under test   so after setting the system time a few hours in the future  the TC timeout expired and the test case was aborted  I had to switch from time time   to time clock   to handle this properly

User · Answer

The short answer is  most of the time time clock   will be better  However  if you re timing some hardware  for example some algorithm you put in the GPU   then time clock   will get rid of this time and time time   is the only solution left   Note  whatever the method used  the timing will depend on factors you cannot control  when will the process switch  how often        this is worse with time time   but exists also with time clock    so you should never run one timing test only  but always run a series of test and look at mean variance of the times

User · Answer

clock   -  floating point number  Return the CPU time or real time since the start of the process or since the first call to clock     This has as much precision as the system records   time   -  floating point number  Return the current time in seconds since the Epoch  Fractions of a second may be present if the system clock provides them   Usually time   is more precise  because operating systems do not store the process running time with the precision they store the system time  ie  actual time

User · Answer

I use this code to compare 2 methods  My OS is windows 8   processor core i5   RAM 4GB import time  def t time        start time time       time sleep 0 1      return  time time  -start    def t clock        start time clock       time sleep 0 1      return  time clock  -start      counter time 0 counter clock 0  for i in range 1 100       counter time    t time        for i in range 1 100           counter clock    t clock    print  quot time     quot  counter time 100 print  quot clock     quot  counter clock 100  output  time     0 0993799996376  clock     0 0993572257367

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