Fastest way to get system uptime in Python in Linux

Question

I\'m looking for a fast and lightweight way to read system uptime from a Python script. Is there a way to call the sysinfo Linux system call from Python?

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Answer 1

I don't think you can get much faster than using ctypes to call sysinfo() but in my tests, its slower than /proc. Those linux system programmers seem to know what they are doing!

import ctypes
import struct

def uptime3():
    libc = ctypes.CDLL('libc.so.6')
    buf = ctypes.create_string_buffer(4096) # generous buffer to hold
                                            # struct sysinfo
    if libc.sysinfo(buf) != 0:
        print('failed')
        return -1

    uptime = struct.unpack_from('@l', buf.raw)[0]
    return uptime

Running your two tests plus mine on my slow laptop, I got:

>>> print(timeit.timeit('ut.uptime1()', setup="import uptimecalls as ut", number=1000))
5.284219555993332
>>> print(timeit.timeit('ut.uptime2()', setup="import uptimecalls as ut", number=1000))
0.1044210599939106
>>> print(timeit.timeit('ut.uptime3()', setup="import uptimecalls as ut", number=1000))
0.11733305400412064

UPDATE

Most of the time is spent pulling in libc and creating the buffer. If you plan to make the call repeatedly over time, then you can pull those steps out of the function and measure just the system call. In that case, this solution is the clear winner:

uptime1: 5.066633300986723
uptime2: 0.11561189399799332
uptime3: 0.007740753993857652