函数功能说明：
指定时间间隔（day,hour,min,second）一个或多个选项，例如，从现在开始延迟 5分钟/1小时，运行一个hello函数。
from datetime import date, time, datetime, timedelta
import time
def hello():
print "hello world."
def runTask(func, day=0, hour=0, min=5, second=0):
# get current time
now = datetime.now()
strnow = now.strftime('%Y-%m-%d %H:%M:%S')
print "now:",strnow
# get net_run time
period = timedelta(days=day, hours=hour, minutes=min, seconds=second)
next_time = now + period
strnext_time = next_time.strftime('%Y-%m-%d %H:%M:%S')
print "next run:",strnext_time
while True:
now = datetime.now()
strnow = now.strftime('%Y-%m-%d %H:%M:%S')
# if system time eq next_time run the specific task(hello func)
if str(strnow) == str(strnext_time):
print strnow
func()
print "task done."
break
runTask(hello, min=3)
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