python 时间差的计算

import time
import datetime

start = datetime.datetime.now()
time.sleep(30)
end = datetime.datetime.now()

print (end-start).days # 0 天数
print (end-start).total_seconds() # 30.029522 精确秒数
print (end-start).seconds # 30 秒数
print (end-start).microseconds # 29522 毫秒数

import datetimenow = datetime.datetime.now()three_days_ago = now + datetime.timedelta(days=-3)three_weeks_ago = now + datetime.timedelta(weeks=-3)print now # datetime.datetime(2016, 12, 22, 11, 24, 49, 987171)print three_days_ago # datetime.datetime(2016, 12, 19, 11, 24, 49, 987171)print three_weeks_ago # datetime.datetime(2016, 12, 1, 11, 24, 49, 987171)

import datetimenow = datetime.datetime.now()three_days_later = now + datetime.timedelta(days=3)three_weeks_later = now + datetime.timedelta(weeks=3)print now # datetime.datetime(2016, 12, 22, 11, 24, 49, 987171)print three_days_later # datetime.datetime(2016, 12, 25, 11, 24, 49, 987171)print three_weeks_later # datetime.datetime(2017, 1, 12, 11, 24, 49, 987171)