Solution to the problem of obtaining millisecond time by python

According to one statement on the Internet,

Obtaining ms level system time in python can be obtained in the following ways:

import datetime
print(datetime.datetime.now().microsecond)

However, the following code test shows that the value returned is not the value of ms, but the value of us:

import datetime 
def getTime_ms():
    return (datetime.datetime.now().hour*3600 +\
            datetime.datetime.now().minute*60+\
            datetime.datetime.now().second )*1000+\
           datetime.datetime.now().microsecond/1000
 
def timetime():
    t = getTime_ms()
    while getTime_ms() - t < 500:
        pass
    a = getTime_ms()
    print(t, a, a- t) 
  
if __name__ == '__main__': 
    from timeit import timeit
    t = timeit('timetime()', 'from __main__ import timetime', number=1)
    print(t)

Print results

(35460614, 35461114, 500) 0.499531984329

The above experiment is not very intuitive, change it to an intuitive point:

def timetime():
    t1 = datetime.datetime.now()
    while 1:
        t2 = datetime.datetime.now()
        if (t2 - t1).microseconds >= 1:
            print(t2,t2.microsecond,t1,t1.microsecond,(t2-t1).seconds)
            break 
 
if __name__ == '__main__':
    from timeit import timeit
    t = timeit('timetime()', 'from __main__ import timetime', number=1)
    print(t)
    #print (datetime.datetime.now())

Output

(datetime.datetime(2019, 4, 3, 10, 6, 20, 461882), 461882, datetime.datetime(2019, 4, 3, 10, 6, 20, 461863), 461863, 0) 7.10487365723e-05

def timetime():
    t1 = datetime.datetime.now()
    while 1:
        t2 = datetime.datetime.now()
        if (t2 - t1).microseconds >= 1000:
            print(t2,t2.microsecond,t1,t1.microsecond,(t2-t1).seconds)
            break 
 
if __name__ == '__main__':
    from timeit import timeit
    t = timeit('timetime()', 'from __main__ import timetime', number=1)
    print(t)
    #print (datetime.datetime.now())

Output

(datetime.datetime(2019, 4, 3, 10, 13, 52, 76548), 76548, datetime.datetime(2019, 4, 3, 10, 13, 52, 75547), 75547, 0) 0.00104904174805

Supplement: Python datetime Remove milliseconds to return to current time

The datetime module returns the current time

import datetime
if __name__ == '__main__':
    a = datetime.datetime.now().replace(microsecond=0)
    print(a, type(a))

Operation result:

2020-05-22 12:13:42 < class 'datetime.datetime' > Process finished with exit code 0