Simulate NMEA RMC stream with leap second

nmealeap.py

#!/usr/bin/python
# nmealeap.py [+1|-1]

import time, math, sys

month=6
day=30
hour=23
minute=59
second=30

leap=int(sys.argv[1])

for i in range(120):
    while True:
        f = math.modf(time.time())[0]
        if f >= 0.1 and f <= 0.4:
            break
        time.sleep(0.1)
    second += 1
    if (minute == 59 and second == 60 + leap) or (minute != 59 and second > 59):
        second = 0
        minute += 1
    if minute > 59:
        minute = 0
        hour += 1
    if hour > 23:
        hour = 0
        day += 1
    if day > 30:
        day = 1
        month += 1

    msg="GNRMC,{:02d}{:02d}{:02d}.00,A,0000.00000,N,00000.00000,W,0.000,,{:02d}{:02d}24,,,A,V".format(
            hour, minute, second, day, month)

    csum = 0
    for c in msg:
        csum ^= ord(c)

    print("${}*{:02X}\r\n".format(msg, csum), end='', flush=True)

    time.sleep(0.5)