How can I get millisecond and microsecond-resolution timestamps in Python?

python timestamp delay timing milliseconds
Gabriel Staples picture Gabriel Staples · Jul 12, 2016 · Viewed 19.8k times · Source

UPDATE: I finally figured this out and would like to share the knowledge and save someone a bunch of time, so see my answer below. I've finally figured it out for Linux too, including for pre-Python 3.3 (ex: for the Raspberry Pi), and I've posted my new module/code in my answer below.

Original question:

How do I get millisecond and microsecond-resolution timestamps in Python?
I'd also like the Arduino-like delay() (which delays in milliseconds) and delayMicroseconds() functions.

Note to the community:

Please don't mark this question as a duplicate and say it has an answer elsewhere when it definitely does not.

This question was incorrectly closed and marked as a duplicate of this one in approx. Sept. 2018 (see screenshot just below). It was then finally re-opened two years later on 23 Aug. 2020. Thank you for re-opening it! It's not a duplicate. That was a mistake. See more information on why just below.

enter image description here

It says, "This question already has an answer here." Unfortunately, that's just not true. I read those answers before asking this question, years ago, and they don't answer my question nor meet my needs. They are just as inapplicable to my question as is the most downvoted answer here, which is greyed out because it is unfortunately wrong since it relies on the time module, which prior to Python 3.3 did NOT have any type of guaranteed resolution whatsoever:

Please re-open my question. It is not a duplicate. It does not have a prior answer from another question. The question linked as already containing an answer relies on the time module, and even states its resolution is all over the place. The most upvoted answer there quotes a Windows resolution using their answer of 16 ms, which is 32000 times worse than my answer I provided here (0.5 us resolution). Again, I needed 1 ms and 1 us (or similar) resolutions, NOT 16000 us resolution. Therefore, it is not a duplicate.

Related:

  1. [my own answer on how to do the same thing (get ms and us-resolution timestamps) in C++] Getting an accurate execution time in C++ (micro seconds)

Answer

Gabriel Staples picture Gabriel Staples · Jul 12, 2016

For Windows: Here's a fully-functional module for both Linux (works with pre-Python 3.3 too) and Windows:

Functions and code samples.
Functions include:

  • micros()
  • millis()
  • delay()
  • delayMicroseconds()

Python code module:

"""
GS_timing.py
-create some low-level Arduino-like millis() (milliseconds) and micros() 
 (microseconds) timing functions for Python 
By Gabriel Staples
http://www.ElectricRCAircraftGuy.com 
-click "Contact me" at the top of my website to find my email address 
Started: 11 July 2016 
Updated: 13 Aug 2016 

History (newest on top): 
20160813 - v0.2.0 created - added Linux compatibility, using ctypes, so that it's compatible with pre-Python 3.3 (for Python 3.3 or later just use the built-in time functions for Linux, shown here: https://docs.python.org/3/library/time.html)
-ex: time.clock_gettime(time.CLOCK_MONOTONIC_RAW)
20160711 - v0.1.0 created - functions work for Windows *only* (via the QPC timer)

References:
WINDOWS:
-personal (C++ code): GS_PCArduino.h
1) Acquiring high-resolution time stamps (Windows)
   -https://msdn.microsoft.com/en-us/library/windows/desktop/dn553408(v=vs.85).aspx
2) QueryPerformanceCounter function (Windows)
   -https://msdn.microsoft.com/en-us/library/windows/desktop/ms644904(v=vs.85).aspx
3) QueryPerformanceFrequency function (Windows)
   -https://msdn.microsoft.com/en-us/library/windows/desktop/ms644905(v=vs.85).aspx
4) LARGE_INTEGER union (Windows)
   -https://msdn.microsoft.com/en-us/library/windows/desktop/aa383713(v=vs.85).aspx

-*****https://stackoverflow.com/questions/4430227/python-on-win32-how-to-get-
absolute-timing-cpu-cycle-count
   
LINUX:
-https://stackoverflow.com/questions/1205722/how-do-i-get-monotonic-time-durations-in-python


"""

import ctypes, os 

#Constants:
VERSION = '0.2.0'

#-------------------------------------------------------------------
#FUNCTIONS:
#-------------------------------------------------------------------
#OS-specific low-level timing functions:
if (os.name=='nt'): #for Windows:
    def micros():
        "return a timestamp in microseconds (us)"
        tics = ctypes.c_int64()
        freq = ctypes.c_int64()

        #get ticks on the internal ~2MHz QPC clock
        ctypes.windll.Kernel32.QueryPerformanceCounter(ctypes.byref(tics)) 
        #get the actual freq. of the internal ~2MHz QPC clock
        ctypes.windll.Kernel32.QueryPerformanceFrequency(ctypes.byref(freq))  
        
        t_us = tics.value*1e6/freq.value
        return t_us
        
    def millis():
        "return a timestamp in milliseconds (ms)"
        tics = ctypes.c_int64()
        freq = ctypes.c_int64()

        #get ticks on the internal ~2MHz QPC clock
        ctypes.windll.Kernel32.QueryPerformanceCounter(ctypes.byref(tics)) 
        #get the actual freq. of the internal ~2MHz QPC clock 
        ctypes.windll.Kernel32.QueryPerformanceFrequency(ctypes.byref(freq)) 
        
        t_ms = tics.value*1e3/freq.value
        return t_ms

elif (os.name=='posix'): #for Linux:

    #Constants:
    CLOCK_MONOTONIC_RAW = 4 # see <linux/time.h> here: https://github.com/torvalds/linux/blob/master/include/uapi/linux/time.h
    
    #prepare ctype timespec structure of {long, long}
    class timespec(ctypes.Structure):
        _fields_ =\
        [
            ('tv_sec', ctypes.c_long),
            ('tv_nsec', ctypes.c_long)
        ]
        
    #Configure Python access to the clock_gettime C library, via ctypes:
    #Documentation:
    #-ctypes.CDLL: https://docs.python.org/3.2/library/ctypes.html
    #-librt.so.1 with clock_gettime: https://docs.oracle.com/cd/E36784_01/html/E36873/librt-3lib.html #-
    #-Linux clock_gettime(): http://linux.die.net/man/3/clock_gettime
    librt = ctypes.CDLL('librt.so.1', use_errno=True)
    clock_gettime = librt.clock_gettime
    #specify input arguments and types to the C clock_gettime() function
    # (int clock_ID, timespec* t)
    clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]

    def monotonic_time():
        "return a timestamp in seconds (sec)"
        t = timespec()
        #(Note that clock_gettime() returns 0 for success, or -1 for failure, in
        # which case errno is set appropriately)
        #-see here: http://linux.die.net/man/3/clock_gettime
        if clock_gettime(CLOCK_MONOTONIC_RAW , ctypes.pointer(t)) != 0:
            #if clock_gettime() returns an error
            errno_ = ctypes.get_errno()
            raise OSError(errno_, os.strerror(errno_))
        return t.tv_sec + t.tv_nsec*1e-9 #sec 
    
    def micros():
        "return a timestamp in microseconds (us)"
        return monotonic_time()*1e6 #us 
        
    def millis():
        "return a timestamp in milliseconds (ms)"
        return monotonic_time()*1e3 #ms 

#Other timing functions:
def delay(delay_ms):
    "delay for delay_ms milliseconds (ms)"
    t_start = millis()
    while (millis() - t_start < delay_ms):
      pass #do nothing 
    return

def delayMicroseconds(delay_us):
    "delay for delay_us microseconds (us)"
    t_start = micros()
    while (micros() - t_start < delay_us):
      pass #do nothing 
    return 
        
#-------------------------------------------------------------------
#EXAMPLES:
#-------------------------------------------------------------------
#Only executute this block of code if running this module directly,
#*not* if importing it
#-see here: http://effbot.org/pyfaq/tutor-what-is-if-name-main-for.htm
if __name__ == "__main__": #if running this module as a stand-alone program

    #print loop execution time 100 times, using micros()
    tStart = micros() #us
    for x in range(0, 100):
        tNow = micros() #us
        dt = tNow - tStart #us; delta time 
        tStart = tNow #us; update 
        print("dt(us) = " + str(dt))

    #print loop execution time 100 times, using millis()
    print("\n")
    tStart = millis() #ms
    for x in range(0, 100):
        tNow = millis() #ms
        dt = tNow - tStart #ms; delta time 
        tStart = tNow #ms; update 
        print("dt(ms) = " + str(dt))
        
    #print a counter once per second, for 5 seconds, using delay 
    print("\nstart")
    for i in range(1,6):
        delay(1000)
        print(i)

    #print a counter once per second, for 5 seconds, using delayMicroseconds
    print("\nstart")
    for i in range(1,6):
        delayMicroseconds(1000000)
        print(i)

If you know how to get the above millisecond and microsecond-resolution timestamps in Linux, please post, as that would be very helpful too.

This works for Linux too, including in pre-Python 3.3, since I'm using C functions via the ctypes module in order to read the time stamps.

(Note: code above originally posted here: http://www.electricrcaircraftguy.com/2016/07/arduino-like-millisecond-and-microsecond-timestamps-in-python.html)

Special thanks to @ArminRonacher for his brilliant pre-Python 3.3 Linux answer here: https://stackoverflow.com/a/1205762/4561887

Update: prior to Python 3.3, the built-in Python time library (https://docs.python.org/3.5/library/time.html) didn't have any explicitly high-resolution functions. Now, however it does provide other options, including some high-resolution functions.

My module above, however, provides high-resolution timestamps for Python code before Python 3.3, as well as after, and it does so on both Linux and Windows.

Here's an example of what I mean, showing that the time.sleep() function is NOT necessarily a high-resolution function. *On my Windows machine, it's resolution is perhaps 8ms at best, whereas my module above has 0.5us resolution (16000 times better!) on the same machine.

Code demonstration:

import time
import GS_timing as timing

def delayMicroseconds(n):
    time.sleep(n / 1000000.)

def delayMillisecond(n):
    time.sleep(n / 1000.)

t_start = 0
t_end = 0

#using time.sleep
print('using time.sleep')
print('delayMicroseconds(1)')
for x in range(10):
    t_start = timing.micros() #us 
    delayMicroseconds(1)
    t_end = timing.micros() #us
    print('dt (us) = ' + str(t_end - t_start))
print('delayMicroseconds(2000)')
for x in range(10):
    t_start = timing.micros() #us 
    delayMicroseconds(2000)
    t_end = timing.micros() #us
    print('dt (us) = ' + str(t_end - t_start))
  
#using GS_timing
print('\nusing GS_timing')
print('timing.delayMicroseconds(1)')
for x in range(10):
    t_start = timing.micros() #us 
    timing.delayMicroseconds(1)
    t_end = timing.micros() #us
    print('dt (us) = ' + str(t_end - t_start))
print('timing.delayMicroseconds(2000)')
for x in range(10):
    t_start = timing.micros() #us 
    timing.delayMicroseconds(2000)
    t_end = timing.micros() #us
    print('dt (us) = ' + str(t_end - t_start))

SAMPLE RESULTS ON MY WINDOWS 8.1 MACHINE (notice how much worse time.sleep does):

using time.sleep
delayMicroseconds(1)
dt (us) = 2872.059814453125
dt (us) = 886.3939208984375
dt (us) = 770.4649658203125
dt (us) = 1138.7698974609375
dt (us) = 1426.027099609375
dt (us) = 734.557861328125
dt (us) = 10617.233642578125
dt (us) = 9594.90576171875
dt (us) = 9155.299560546875
dt (us) = 9520.526611328125
delayMicroseconds(2000)
dt (us) = 8799.3056640625
dt (us) = 9609.2685546875
dt (us) = 9679.5439453125
dt (us) = 9248.145263671875
dt (us) = 9389.721923828125
dt (us) = 9637.994262695312
dt (us) = 9616.450073242188
dt (us) = 9592.853881835938
dt (us) = 9465.639892578125
dt (us) = 7650.276611328125

using GS_timing
timing.delayMicroseconds(1)
dt (us) = 53.3477783203125
dt (us) = 36.93310546875
dt (us) = 36.9329833984375
dt (us) = 34.8812255859375
dt (us) = 35.3941650390625
dt (us) = 40.010986328125
dt (us) = 38.4720458984375
dt (us) = 56.425537109375
dt (us) = 35.9072265625
dt (us) = 36.420166015625
timing.delayMicroseconds(2000)
dt (us) = 2039.526611328125
dt (us) = 2046.195068359375
dt (us) = 2033.8841552734375
dt (us) = 2037.4747314453125
dt (us) = 2032.34521484375
dt (us) = 2086.2059326171875
dt (us) = 2035.4229736328125
dt (us) = 2051.32470703125
dt (us) = 2040.03955078125
dt (us) = 2027.215576171875

SAMPLE RESULTS ON MY RASPBERRY PI VERSION 1 B+ (notice that the results between using time.sleep and my module are basically identical...apparently the low-level functions in time are already accessing better-resolution timers here, since it's a Linux machine (running Raspbian)...BUT in my GS_timing module I am explicitly calling the CLOCK_MONOTONIC_RAW timer. Who knows what's being used otherwise):

using time.sleep
delayMicroseconds(1)
dt (us) = 1022.0
dt (us) = 417.0
dt (us) = 407.0
dt (us) = 450.0
dt (us) = 2078.0
dt (us) = 393.0
dt (us) = 1297.0
dt (us) = 878.0
dt (us) = 1135.0
dt (us) = 2896.0
delayMicroseconds(2000)
dt (us) = 2746.0
dt (us) = 2568.0
dt (us) = 2512.0
dt (us) = 2423.0
dt (us) = 2454.0
dt (us) = 2608.0
dt (us) = 2518.0
dt (us) = 2569.0
dt (us) = 2548.0
dt (us) = 2496.0

using GS_timing
timing.delayMicroseconds(1)
dt (us) = 572.0
dt (us) = 673.0
dt (us) = 1084.0
dt (us) = 561.0
dt (us) = 728.0
dt (us) = 576.0
dt (us) = 556.0
dt (us) = 584.0
dt (us) = 576.0
dt (us) = 578.0
timing.delayMicroseconds(2000)
dt (us) = 2741.0
dt (us) = 2466.0
dt (us) = 2522.0
dt (us) = 2810.0
dt (us) = 2589.0
dt (us) = 2681.0
dt (us) = 2546.0
dt (us) = 3090.0
dt (us) = 2600.0
dt (us) = 2400.0

Related:

  1. [my own answer on how to do the same thing (get ms and us-resolution timestamps) in C++] Getting an accurate execution time in C++ (micro seconds)

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